diff --git a/Mesh/bakmeshGRegionBoundaryRecovery.cpp b/Mesh/bakmeshGRegionBoundaryRecovery.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..5c3118dc95557d08d4c9a8f448f4be74371affc3
--- /dev/null
+++ b/Mesh/bakmeshGRegionBoundaryRecovery.cpp
@@ -0,0 +1 @@
+dummy file
diff --git a/Mesh/meshGRegionBoundaryRecovery.cpp b/Mesh/meshGRegionBoundaryRecovery.cpp
index 62b27c30e5275bf8ec373266cfaeabd00e86fa47..724358da0d858ddc64056cdeb60be0190e290554 100644
--- a/Mesh/meshGRegionBoundaryRecovery.cpp
+++ b/Mesh/meshGRegionBoundaryRecovery.cpp
@@ -33,27 +33,6 @@ bool meshGRegionBoundaryRecovery(GRegion *gr)
 class tetgenio{
 public:
 
-  typedef struct {
-    int *vertexlist;
-    int numberofvertices;
-  } polygon;
-
-  // A "facet" describes a polygonal region possibly with holes, edges, and
-  //   points floating in it.  Each facet consists of a list of polygons and
-  //   a list of hole points (which lie strictly inside holes).
-  typedef struct {
-    polygon *polygonlist;
-    int numberofpolygons;
-    REAL *holelist;
-    int numberofholes;
-  } facet;
-
-  typedef struct{
-    REAL uv[2];
-    int tag;
-    int type;
-  } pointparam;
-
   int firstnumber;
   int numberofpointattributes;
 
@@ -68,7 +47,6 @@ public:
   int numberofpoints;
   int *pointlist;
   int *pointattributelist;
-  pointparam *pointparamlist;
 
   int numberofpointmakers;
   int *pointmarkerlist;
@@ -80,10 +58,6 @@ public:
   int *edgelist;
   int *edgemarkerlist;
 
-  int numberoffacets;
-  facet *facetlist;
-  int *facetmarkerlist;
-
   int numberofholes;
   REAL *holelist;
 
@@ -104,7 +78,6 @@ public:
     numberofpoints = 0;
     pointlist = 0;
     pointattributelist = 0;
-    pointparamlist = 0;
     numberofpointmakers = 0;
     pointmarkerlist = 0;
     numberofpointmtrs = 0;
@@ -112,9 +85,6 @@ public:
     numberofedges = 0;
     edgelist = 0;
     edgemarkerlist = 0;
-    numberoffacets = 0;
-    facetlist = 0;
-    facetmarkerlist = 0;
     numberofholes = 0;
     holelist = 0;
     numberofregions = 0;
@@ -149,7 +119,7 @@ bool tetgenmesh::reconstructmesh(void *p)
 
   in = new tetgenio();
   b = new tetgenbehavior();
-  char *opt = "pY";
+  char opt[] = "pY";
   b->parse_commandline(opt);
 
   bool returnValue (true);
@@ -537,7 +507,7 @@ bool tetgenmesh::reconstructmesh(void *p)
     insegments = subsegs->items;
 
     if (0) {
-      //outsurfacemesh("dump");
+      outsurfacemesh("dump");
     }
 
   } // meshsurface()
@@ -624,7 +594,9 @@ bool tetgenmesh::reconstructmesh(void *p)
   }
 
   // Debug
-  //outmesh2medit("dump");
+  if (0) {
+    //outmesh2medit("dump");
+  }
   ////////////////////////////////////////////////////////
 
 {
@@ -869,4 +841,213 @@ bool tetgenmesh::reconstructmesh(void *p)
 
 }
 
+// Dump the input surface mesh.
+// 'mfilename' is a filename without suffix.
+void tetgenmesh::outsurfacemesh(const char* mfilename)
+{
+  FILE *outfile = NULL;
+  char sfilename[256];
+  int firstindex;
+
+  point pointloop;
+  int pointnumber;
+  strcpy(sfilename, mfilename);
+  strcat(sfilename, ".node");
+  outfile = fopen(sfilename, "w");
+  if (!b->quiet) {
+    printf("Writing %s.\n", sfilename);
+  }
+  fprintf(outfile, "%ld  3  0  0\n", points->items);
+  // Determine the first index (0 or 1).
+  firstindex = b->zeroindex ? 0 : in->firstnumber;
+  points->traversalinit();
+  pointloop = pointtraverse();
+  pointnumber = firstindex; // in->firstnumber;
+  while (pointloop != (point) NULL) {
+    // Point number, x, y and z coordinates.
+    fprintf(outfile, "%4d    %.17g  %.17g  %.17g", pointnumber,
+            pointloop[0], pointloop[1], pointloop[2]);
+    fprintf(outfile, "\n");
+    pointloop = pointtraverse();
+    pointnumber++;
+  }
+  fclose(outfile);
+
+  face faceloop;
+  point torg, tdest, tapex;
+  strcpy(sfilename, mfilename);
+  strcat(sfilename, ".smesh");
+  outfile = fopen(sfilename, "w");
+  if (!b->quiet) {
+    printf("Writing %s.\n", sfilename);
+  }
+  int shift = 0; // Default no shiftment.
+  if ((in->firstnumber == 1) && (firstindex == 0)) {
+    shift = 1; // Shift the output indices by 1.
+  }
+  fprintf(outfile, "0 3 0 0\n");
+  fprintf(outfile, "%ld  1\n", subfaces->items);
+  subfaces->traversalinit();
+  faceloop.sh = shellfacetraverse(subfaces);
+  while (faceloop.sh != (shellface *) NULL) {
+    torg = sorg(faceloop);
+    tdest = sdest(faceloop);
+    tapex = sapex(faceloop);
+    fprintf(outfile, "3   %4d  %4d  %4d  %d\n",
+            pointmark(torg) - shift, pointmark(tdest) - shift,
+            pointmark(tapex) - shift, shellmark(faceloop));
+    faceloop.sh = shellfacetraverse(subfaces);
+  }
+  fprintf(outfile, "0\n");
+  fprintf(outfile, "0\n");
+  fclose(outfile);
+
+  face edgeloop;
+  int edgenumber;
+  strcpy(sfilename, mfilename);
+  strcat(sfilename, ".edge");
+  outfile = fopen(sfilename, "w");
+  if (!b->quiet) {
+    printf("Writing %s.\n", sfilename);
+  }
+  fprintf(outfile, "%ld  1\n", subsegs->items);
+  subsegs->traversalinit();
+  edgeloop.sh = shellfacetraverse(subsegs);
+  edgenumber = firstindex; // in->firstnumber;
+  while (edgeloop.sh != (shellface *) NULL) {
+    torg = sorg(edgeloop);
+    tdest = sdest(edgeloop);
+    fprintf(outfile, "%5d   %4d  %4d  %d\n", edgenumber,
+            pointmark(torg) - shift, pointmark(tdest) - shift,
+            shellmark(edgeloop));
+    edgenumber++;
+    edgeloop.sh = shellfacetraverse(subsegs);
+  }
+  fclose(outfile);
+}
+
+void tetgenmesh::outmesh2medit(const char* mfilename)
+{
+  FILE *outfile;
+  char mefilename[256];
+  tetrahedron* tetptr;
+  triface tface, tsymface;
+  face segloop, checkmark;
+  point ptloop, p1, p2, p3, p4;
+  long ntets, faces;
+  int shift = 0;
+  int marker;
+
+  if (mfilename != (char *) NULL && mfilename[0] != '\0') {
+    strcpy(mefilename, mfilename);
+  } else {
+    strcpy(mefilename, "unnamed");
+  }
+  strcat(mefilename, ".mesh");
+
+  if (!b->quiet) {
+    printf("Writing %s.\n", mefilename);
+  }
+  outfile = fopen(mefilename, "w");
+  if (outfile == (FILE *) NULL) {
+    printf("File I/O Error:  Cannot create file %s.\n", mefilename);
+    return;
+  }
+
+  fprintf(outfile, "MeshVersionFormatted 1\n");
+  fprintf(outfile, "\n");
+  fprintf(outfile, "Dimension\n");
+  fprintf(outfile, "3\n");
+  fprintf(outfile, "\n");
+
+  fprintf(outfile, "\n# Set of mesh vertices\n");
+  fprintf(outfile, "Vertices\n");
+  fprintf(outfile, "%ld\n", points->items);
+
+  points->traversalinit();
+  ptloop = pointtraverse();
+  //pointnumber = 1;
+  while (ptloop != (point) NULL) {
+    // Point coordinates.
+    fprintf(outfile, "%.17g  %.17g  %.17g", ptloop[0], ptloop[1], ptloop[2]);
+    fprintf(outfile, "    0\n");
+    //setpointmark(ptloop, pointnumber);
+    ptloop = pointtraverse();
+    //pointnumber++;
+  }
+
+  // Medit need start number form 1.
+  if (in->firstnumber == 1) {
+    shift = 0;
+  } else {
+    shift = 1;
+  }
+
+  // Compute the number of faces.
+  ntets = tetrahedrons->items - hullsize;
+  faces = (ntets * 4l + hullsize) / 2l;
+
+  /*
+  fprintf(outfile, "\n# Set of Triangles\n");
+  fprintf(outfile, "Triangles\n");
+  fprintf(outfile, "%ld\n", faces);
+
+  tetrahedrons->traversalinit();
+  tface.tet = tetrahedrontraverse();
+  while (tface.tet != (tetrahedron *) NULL) {
+    for (tface.ver = 0; tface.ver < 4; tface.ver ++) {
+      fsym(tface, tsymface);
+      if (ishulltet(tsymface) ||
+          (elemindex(tface.tet) < elemindex(tsymface.tet))) {
+        p1 = org (tface);
+        p2 = dest(tface);
+        p3 = apex(tface);
+        fprintf(outfile, "%5d  %5d  %5d",
+          pointmark(p1)+shift, pointmark(p2)+shift, pointmark(p3)+shift);
+        // Check if it is a subface.
+        tspivot(tface, checkmark);
+        if (checkmark.sh == NULL) {
+          marker = 0;  // It is an inner face. It's marker is 0.
+        } else {
+          marker = 1; // The default marker for subface is 1.
+        }
+        fprintf(outfile, "    %d\n", marker);
+      }
+    }
+    tface.tet = tetrahedrontraverse();
+  }
+  */
+
+  fprintf(outfile, "\n# Set of Tetrahedra\n");
+  fprintf(outfile, "Tetrahedra\n");
+  fprintf(outfile, "%ld\n", ntets);
+
+  tetrahedrons->traversalinit();
+  tetptr = tetrahedrontraverse();
+  while (tetptr != (tetrahedron *) NULL) {
+    if (!b->reversetetori) {
+      p1 = (point) tetptr[4];
+      p2 = (point) tetptr[5];
+    } else {
+      p1 = (point) tetptr[5];
+      p2 = (point) tetptr[4];
+    }
+    p3 = (point) tetptr[6];
+    p4 = (point) tetptr[7];
+    fprintf(outfile, "%5d  %5d  %5d  %5d",
+            pointmark(p1)+shift, pointmark(p2)+shift,
+            pointmark(p3)+shift, pointmark(p4)+shift);
+    if (numelemattrib > 0) {
+      fprintf(outfile, "  %.17g", elemattribute(tetptr, 0));
+    } else {
+      fprintf(outfile, "  0");
+    }
+    fprintf(outfile, "\n");
+    tetptr = tetrahedrontraverse();
+  }
+
+  fprintf(outfile, "\nEnd\n");
+  fclose(outfile);
+}
+
 #endif
diff --git a/Mesh/tetgenBR.cxx b/Mesh/tetgenBR.cxx
new file mode 100644
index 0000000000000000000000000000000000000000..2a756fd206d348ffc80c25818d04ebaf24200b17
--- /dev/null
+++ b/Mesh/tetgenBR.cxx
@@ -0,0 +1,17056 @@
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// parse_commandline()    Read the command line, identify switches, and set  //
+//                        up options and file names.                         //
+//                                                                           //
+// 'argc' and 'argv' are the same parameters passed to the function main()   //
+// of a C/C++ program. They together represent the command line user invoked //
+// from an environment in which TetGen is running.                           //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+bool tetgenbehavior::parse_commandline(int argc, char **argv)
+{
+  int startindex;
+  int increment;
+  int meshnumber;
+  int i, j, k;
+  char workstring[1024];
+
+  // First determine the input style of the switches.
+  if (argc == 0) {
+    startindex = 0;                    // Switches are given without a dash.
+    argc = 1;                    // For running the following for-loop once.
+    commandline[0] = '\0';
+  } else {
+    startindex = 1;
+    strcpy(commandline, argv[0]);
+    strcat(commandline, " ");
+  }
+
+  for (i = startindex; i < argc; i++) {
+    // Remember the command line for output.
+    strcat(commandline, argv[i]);
+    strcat(commandline, " ");
+    if (startindex == 1) {
+      // Is this string a filename?
+      if (argv[i][0] != '-') {
+        strncpy(infilename, argv[i], 1024 - 1);
+        infilename[1024 - 1] = '\0';
+        continue;                     
+      }
+    }
+    // Parse the individual switch from the string.
+    for (j = startindex; argv[i][j] != '\0'; j++) {
+      if (argv[i][j] == 'p') {
+        plc = 1;
+        if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+            (argv[i][j + 1] == '.')) {
+          k = 0;
+          while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                 (argv[i][j + 1] == '.')) {
+            j++;
+            workstring[k] = argv[i][j];
+            k++;
+          }
+          workstring[k] = '\0';
+          facet_separate_ang_tol = (REAL) strtod(workstring, (char **) NULL);
+        }
+		if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+              (argv[i][j + 1] == '.')) {
+            k = 0;
+            while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                 (argv[i][j + 1] == '.') || (argv[i][j + 1] == 'e') ||
+                 (argv[i][j + 1] == '-') || (argv[i][j + 1] == '+')) {
+              j++;
+              workstring[k] = argv[i][j];
+              k++;
+            }
+            workstring[k] = '\0';
+            facet_overlap_ang_tol = (REAL) strtod(workstring, (char **) NULL);
+          }
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+              (argv[i][j + 1] == '.')) {
+            k = 0;
+            while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                   (argv[i][j + 1] == '.')) {
+              j++;
+              workstring[k] = argv[i][j];
+              k++;
+            }
+            workstring[k] = '\0';
+            facet_small_ang_tol = (REAL) strtod(workstring, (char **) NULL);
+          }
+        }
+      } else if (argv[i][j] == 's') {
+        psc = 1;
+      } else if (argv[i][j] == 'Y') {
+        nobisect = 1;
+        if ((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) {
+          nobisect_nomerge = (argv[i][j + 1] - '0');
+          j++;
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if ((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) {
+            supsteiner_level = (argv[i][j + 1] - '0');
+            j++;
+          }
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if ((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) {
+            addsteiner_algo = (argv[i][j + 1] - '0');
+            j++;
+          }
+        }
+      } else if (argv[i][j] == 'r') {
+        refine = 1;
+      } else if (argv[i][j] == 'q') {
+        quality = 1;
+        if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+            (argv[i][j + 1] == '.')) {
+          k = 0;
+          while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                 (argv[i][j + 1] == '.')) {
+            j++;
+            workstring[k] = argv[i][j];
+            k++;
+          }
+          workstring[k] = '\0';
+          minratio = (REAL) strtod(workstring, (char **) NULL);
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+              (argv[i][j + 1] == '.')) {
+            k = 0;
+            while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                   (argv[i][j + 1] == '.')) {
+              j++;
+              workstring[k] = argv[i][j];
+              k++;
+            }
+            workstring[k] = '\0';
+            mindihedral = (REAL) strtod(workstring, (char **) NULL);
+          }
+        }
+      } else if (argv[i][j] == 'R') {
+        coarsen = 1;
+        if ((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) {
+          coarsen_param = (argv[i][j + 1] - '0');
+          j++;
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+              (argv[i][j + 1] == '.')) {
+            k = 0;
+            while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                   (argv[i][j + 1] == '.')) {
+              j++;
+              workstring[k] = argv[i][j];
+              k++;
+            }
+            workstring[k] = '\0';
+            coarsen_percent = (REAL) strtod(workstring, (char **) NULL);
+          }
+        }
+      } else if (argv[i][j] == 'w') {
+        weighted = 1;
+        if ((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) {
+          weighted_param = (argv[i][j + 1] - '0');
+          j++;
+        }
+      } else if (argv[i][j] == 'b') {
+        // -b(brio_threshold/brio_ratio/hilbert_limit/hilbert_order)
+        brio_hilbert = 1;
+        if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+            (argv[i][j + 1] == '.')) {
+          k = 0;
+          while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                 (argv[i][j + 1] == '.')) {
+            j++;
+            workstring[k] = argv[i][j];
+            k++;
+          }
+          workstring[k] = '\0';
+          brio_threshold = (int) strtol(workstring, (char **) &workstring, 0);
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+              (argv[i][j + 1] == '.')) {
+            k = 0;
+            while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                   (argv[i][j + 1] == '.')) {
+              j++;
+              workstring[k] = argv[i][j];
+              k++;
+            }
+            workstring[k] = '\0';
+            brio_ratio = (REAL) strtod(workstring, (char **) NULL);
+          }
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+              (argv[i][j + 1] == '.') || (argv[i][j + 1] == '-')) {
+            k = 0;
+            while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                   (argv[i][j + 1] == '.') || (argv[i][j + 1] == '-')) {
+              j++;
+              workstring[k] = argv[i][j];
+              k++;
+            }
+            workstring[k] = '\0';
+            hilbert_limit = (int) strtol(workstring, (char **) &workstring, 0);
+          }
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+              (argv[i][j + 1] == '.') || (argv[i][j + 1] == '-')) {
+            k = 0;
+            while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                   (argv[i][j + 1] == '.') || (argv[i][j + 1] == '-')) {
+              j++;
+              workstring[k] = argv[i][j];
+              k++;
+            }
+            workstring[k] = '\0';
+            hilbert_order = (REAL) strtod(workstring, (char **) NULL);
+          }
+        }
+        if (brio_threshold == 0) { // -b0
+          brio_hilbert = 0; // Turn off BRIO-Hilbert sorting. 
+        }
+        if (brio_ratio >= 1.0) { // -b/1
+          no_sort = 1;
+          brio_hilbert = 0; // Turn off BRIO-Hilbert sorting.
+        }
+      } else if (argv[i][j] == 'l') {
+        incrflip = 1;
+      } else if (argv[i][j] == 'L') {
+        flipinsert = 1;
+      } else if (argv[i][j] == 'm') {
+        metric = 1;
+      } else if (argv[i][j] == 'a') {
+        if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+            (argv[i][j + 1] == '.')) {
+          fixedvolume = 1;
+          k = 0;
+          while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                 (argv[i][j + 1] == '.') || (argv[i][j + 1] == 'e') ||
+                 (argv[i][j + 1] == '-') || (argv[i][j + 1] == '+')) {
+            j++;
+            workstring[k] = argv[i][j];
+            k++;
+          }
+          workstring[k] = '\0';
+          maxvolume = (REAL) strtod(workstring, (char **) NULL);
+        } else {
+          varvolume = 1;
+        }
+      } else if (argv[i][j] == 'A') {
+        regionattrib = 1;
+      } else if (argv[i][j] == 'D') {
+        cdtrefine = 1;
+        if ((argv[i][j + 1] >= '1') && (argv[i][j + 1] <= '3')) {
+          reflevel = (argv[i][j + 1] - '1') + 1; 
+          j++;
+        }
+      } else if (argv[i][j] == 'i') {
+        insertaddpoints = 1;
+      } else if (argv[i][j] == 'd') {
+        diagnose = 1;
+      } else if (argv[i][j] == 'c') {
+        convex = 1;
+      } else if (argv[i][j] == 'M') {
+        nomergefacet = 1;
+        nomergevertex = 1;
+        if ((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '1')) {
+          nomergefacet = (argv[i][j + 1] - '0');
+          j++;
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if ((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '1')) {
+            nomergevertex = (argv[i][j + 1] - '0');
+            j++;
+          }
+        }
+      } else if (argv[i][j] == 'X') {
+        if (argv[i][j + 1] == '1') {
+          nostaticfilter = 1;
+          j++;
+        } else {
+          noexact = 1;
+        }
+      } else if (argv[i][j] == 'z') {
+        if (argv[i][j + 1] == '1') {  // -z1
+          reversetetori = 1;
+          j++;
+        } else {
+          zeroindex = 1; // -z
+        }
+      } else if (argv[i][j] == 'f') {
+        facesout++;
+      } else if (argv[i][j] == 'e') {
+        edgesout++;
+      } else if (argv[i][j] == 'n') {
+        neighout++;
+      } else if (argv[i][j] == 'v') {
+        voroout = 1;
+      } else if (argv[i][j] == 'g') {
+        meditview = 1;
+      } else if (argv[i][j] == 'k') {
+        vtkview = 1;  
+      } else if (argv[i][j] == 'J') {
+        nojettison = 1;
+      } else if (argv[i][j] == 'B') {
+        nobound = 1;
+      } else if (argv[i][j] == 'N') {
+        nonodewritten = 1;
+      } else if (argv[i][j] == 'E') {
+        noelewritten = 1;
+      } else if (argv[i][j] == 'F') {
+        nofacewritten = 1;
+      } else if (argv[i][j] == 'I') {
+        noiterationnum = 1;
+      } else if (argv[i][j] == 'S') {
+        if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+            (argv[i][j + 1] == '.')) {
+          k = 0;
+          while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                 (argv[i][j + 1] == '.') || (argv[i][j + 1] == 'e') ||
+                 (argv[i][j + 1] == '-') || (argv[i][j + 1] == '+')) {
+            j++;
+            workstring[k] = argv[i][j];
+            k++;
+          }
+          workstring[k] = '\0';
+          steinerleft = (int) strtol(workstring, (char **) NULL, 0);
+        }
+      } else if (argv[i][j] == 'o') {
+        if (argv[i][j + 1] == '2') {
+          order = 2;
+          j++;
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+              (argv[i][j + 1] == '.')) {
+            k = 0;
+            while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                   (argv[i][j + 1] == '.')) {
+              j++;
+              workstring[k] = argv[i][j];
+              k++;
+            }
+            workstring[k] = '\0';
+            optmaxdihedral = (REAL) strtod(workstring, (char **) NULL);
+          }
+        }
+      } else if (argv[i][j] == 'O') {
+        if ((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) {
+          optlevel = (argv[i][j + 1] - '0');
+          j++;
+        }
+        if ((argv[i][j + 1] == '/') || (argv[i][j + 1] == ',')) {
+          j++;
+          if ((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '7')) {
+            optscheme = (argv[i][j + 1] - '0');
+            j++;
+          }
+        }
+      } else if (argv[i][j] == 'T') {
+        if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+            (argv[i][j + 1] == '.')) {
+          k = 0;
+          while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                 (argv[i][j + 1] == '.') || (argv[i][j + 1] == 'e') ||
+                 (argv[i][j + 1] == '-') || (argv[i][j + 1] == '+')) {
+            j++;
+            workstring[k] = argv[i][j];
+            k++;
+          }
+          workstring[k] = '\0';
+          epsilon = (REAL) strtod(workstring, (char **) NULL);
+        }
+      } else if (argv[i][j] == 'C') {
+        docheck++;
+      } else if (argv[i][j] == 'Q') {
+        quiet = 1;
+      } else if (argv[i][j] == 'V') {
+        verbose++;
+      } else if (argv[i][j] == 'x') {
+        if (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+            (argv[i][j + 1] == '.')) {
+          k = 0;
+          while (((argv[i][j + 1] >= '0') && (argv[i][j + 1] <= '9')) ||
+                 (argv[i][j + 1] == '.') || (argv[i][j + 1] == 'e') ||
+                 (argv[i][j + 1] == '-') || (argv[i][j + 1] == '+')) {
+            j++;
+            workstring[k] = argv[i][j];
+            k++;
+          }
+          workstring[k] = '\0';
+          tetrahedraperblock = (int) strtol(workstring, (char **) NULL, 0);
+          if (tetrahedraperblock > 8188) {
+            vertexperblock = tetrahedraperblock / 2;
+            shellfaceperblock = vertexperblock / 2;
+          } else {
+            tetrahedraperblock = 8188;
+          }
+        }
+      } else if ((argv[i][j] == 'h') || (argv[i][j] == 'H') ||
+                 (argv[i][j] == '?')) {
+      } else {
+        printf("Warning:  Unknown switch -%c.\n", argv[i][j]);
+      }
+    }
+  }
+
+  if (startindex == 0) {
+    // Set a temporary filename for debugging output.
+    strcpy(infilename, "tetgen-tmpfile");
+  } else {
+    if (infilename[0] == '\0') {
+    }
+    // Recognize the object from file extension if it is available.
+    if (!strcmp(&infilename[strlen(infilename) - 5], ".node")) {
+      infilename[strlen(infilename) - 5] = '\0';
+      object = NODES;
+    } else if (!strcmp(&infilename[strlen(infilename) - 5], ".poly")) {
+      infilename[strlen(infilename) - 5] = '\0';
+      object = POLY;
+      plc = 1;
+    } else if (!strcmp(&infilename[strlen(infilename) - 6], ".smesh")) {
+      infilename[strlen(infilename) - 6] = '\0';
+      object = POLY;
+      plc = 1;
+    } else if (!strcmp(&infilename[strlen(infilename) - 4], ".off")) {
+      infilename[strlen(infilename) - 4] = '\0';
+      object = OFF;
+      plc = 1;
+    } else if (!strcmp(&infilename[strlen(infilename) - 4], ".ply")) {
+      infilename[strlen(infilename) - 4] = '\0';
+      object = PLY;
+      plc = 1;
+    } else if (!strcmp(&infilename[strlen(infilename) - 4], ".stl")) {
+      infilename[strlen(infilename) - 4] = '\0';
+      object = STL;
+      plc = 1;
+    } else if (!strcmp(&infilename[strlen(infilename) - 5], ".mesh")) {
+      infilename[strlen(infilename) - 5] = '\0';
+      object = MEDIT;
+      if (!refine) plc = 1;
+    } else if (!strcmp(&infilename[strlen(infilename) - 4], ".vtk")) {
+      infilename[strlen(infilename) - 4] = '\0';
+      object = VTK;
+      plc = 1;
+    } else if (!strcmp(&infilename[strlen(infilename) - 4], ".ele")) {
+      infilename[strlen(infilename) - 4] = '\0';
+      object = MESH;
+      refine = 1;
+    }
+  }
+
+  if (nobisect && (!plc && !refine)) { // -Y
+    plc = 1; // Default -p option.
+  }
+  if (quality && (!plc && !refine)) { // -q
+    plc = 1; // Default -p option.
+  }
+  if (diagnose && !plc) { // -d
+    plc = 1;
+  }
+  if (refine && !quality) { // -r only
+    // Reconstruct a mesh, no mesh optimization.
+    optlevel = 0;
+  }
+  if (insertaddpoints && (optlevel == 0)) { // with -i option
+    optlevel = 2;
+  }
+  if (coarsen && (optlevel == 0)) { // with -R option
+    optlevel = 2;
+  }
+
+  // Detect improper combinations of switches.
+  if ((refine || plc) && weighted) {
+    printf("Error:  Switches -w cannot use together with -p or -r.\n");
+    return false;
+  }
+
+  if (convex) { // -c
+    if (plc && !regionattrib) {
+      // -A (region attribute) is needed for marking exterior tets (-1).
+      regionattrib = 1; 
+    }
+  }
+
+  // Note: -A must not used together with -r option. 
+  // Be careful not to add an extra attribute to each element unless the
+  //   input supports it (PLC in, but not refining a preexisting mesh).
+  if (refine || !plc) {
+    regionattrib = 0;
+  }
+  // Be careful not to allocate space for element area constraints that 
+  //   will never be assigned any value (other than the default -1.0).
+  if (!refine && !plc) {
+    varvolume = 0;
+  }
+  // If '-a' or '-aa' is in use, enable '-q' option too.
+  if (fixedvolume || varvolume) {
+    if (quality == 0) {
+      quality = 1;
+      if (!plc && !refine) {
+        plc = 1; // enable -p.
+      }
+    }
+  }
+  // No user-specified dihedral angle bound. Use default ones.
+  if (!quality) {
+    if (optmaxdihedral < 179.0) {
+      if (nobisect) {  // with -Y option
+        optmaxdihedral = 179.0;
+      } else { // -p only
+        optmaxdihedral = 179.999;
+      }
+    }
+    if (optminsmtdihed < 179.999) {
+      optminsmtdihed = 179.999;
+    }
+    if (optminslidihed < 179.999) {
+      optminslidihed = 179.999;
+    }
+  }
+
+  increment = 0;
+  strcpy(workstring, infilename);
+  j = 1;
+  while (workstring[j] != '\0') {
+    if ((workstring[j] == '.') && (workstring[j + 1] != '\0')) {
+      increment = j + 1;
+    }
+    j++;
+  }
+  meshnumber = 0;
+  if (increment > 0) {
+    j = increment;
+    do {
+      if ((workstring[j] >= '0') && (workstring[j] <= '9')) {
+        meshnumber = meshnumber * 10 + (int) (workstring[j] - '0');
+      } else {
+        increment = 0;
+      }
+      j++;
+    } while (workstring[j] != '\0');
+  }
+  if (noiterationnum) {
+    strcpy(outfilename, infilename);
+  } else if (increment == 0) {
+    strcpy(outfilename, infilename);
+    strcat(outfilename, ".1");
+  } else {
+    workstring[increment] = '%';
+    workstring[increment + 1] = 'd';
+    workstring[increment + 2] = '\0';
+    sprintf(outfilename, workstring, meshnumber + 1);
+  }
+  // Additional input file name has the end ".a".
+  strcpy(addinfilename, infilename);
+  strcat(addinfilename, ".a");
+  // Background filename has the form "*.b.ele", "*.b.node", ...
+  strcpy(bgmeshfilename, infilename);
+  strcat(bgmeshfilename, ".b");
+
+  return true;
+}
+
+////                                                                       ////
+////                                                                       ////
+//// behavior_cxx /////////////////////////////////////////////////////////////
+
+//// mempool_cxx //////////////////////////////////////////////////////////////
+////                                                                       ////
+////                                                                       ////
+
+// Initialize fast lookup tables for mesh maniplulation primitives.
+
+int tetgenmesh::bondtbl[12][12] = {{0,},};
+int tetgenmesh::enexttbl[12] = {0,};
+int tetgenmesh::eprevtbl[12] = {0,};
+int tetgenmesh::enextesymtbl[12] = {0,};
+int tetgenmesh::eprevesymtbl[12] = {0,};
+int tetgenmesh::eorgoppotbl[12] = {0,};
+int tetgenmesh::edestoppotbl[12] = {0,};
+int tetgenmesh::fsymtbl[12][12] = {{0,},};
+int tetgenmesh::facepivot1[12] = {0,};
+int tetgenmesh::facepivot2[12][12] = {{0,},};
+int tetgenmesh::tsbondtbl[12][6] = {{0,},};
+int tetgenmesh::stbondtbl[12][6] = {{0,},};
+int tetgenmesh::tspivottbl[12][6] = {{0,},};
+int tetgenmesh::stpivottbl[12][6] = {{0,},};
+
+// Table 'esymtbl' takes an directed edge (version) as input, returns the
+//   inversed edge (version) of it.
+
+int tetgenmesh::esymtbl[12] = {9, 6, 11, 4, 3, 7, 1, 5, 10, 0, 8, 2};
+
+// The following four tables give the 12 permutations of the set {0,1,2,3}.
+//   An offset 4 is added to each element for a direct access of the points
+//   in the tetrahedron data structure.
+
+int tetgenmesh:: orgpivot[12] = {7, 7, 5, 5, 6, 4, 4, 6, 5, 6, 7, 4};
+int tetgenmesh::destpivot[12] = {6, 4, 4, 6, 5, 6, 7, 4, 7, 7, 5, 5};
+int tetgenmesh::apexpivot[12] = {5, 6, 7, 4, 7, 7, 5, 5, 6, 4, 4, 6};
+int tetgenmesh::oppopivot[12] = {4, 5, 6, 7, 4, 5, 6, 7, 4, 5, 6, 7};
+
+// The twelve versions correspond to six undirected edges. The following two
+//   tables map a version to an undirected edge and vice versa.
+
+int tetgenmesh::ver2edge[12] = {0, 1, 2, 3, 3, 5, 1, 5, 4, 0, 4, 2};
+int tetgenmesh::edge2ver[ 6] = {0, 1, 2, 3, 8, 5};
+
+// Edge versions whose apex or opposite may be dummypoint.
+
+int tetgenmesh::epivot[12] = {4, 5, 2, 11, 4, 5, 2, 11, 4, 5, 2, 11};
+
+
+// Table 'snextpivot' takes an edge version as input, returns the next edge
+//   version in the same edge ring.
+
+int tetgenmesh::snextpivot[6] = {2, 5, 4, 1, 0, 3};
+
+// The following three tables give the 6 permutations of the set {0,1,2}.
+//   An offset 3 is added to each element for a direct access of the points
+//   in the triangle data structure.
+
+int tetgenmesh::sorgpivot [6] = {3, 4, 4, 5, 5, 3};
+int tetgenmesh::sdestpivot[6] = {4, 3, 5, 4, 3, 5};
+int tetgenmesh::sapexpivot[6] = {5, 5, 3, 3, 4, 4};
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// inittable()    Initialize the look-up tables.                             //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::inittables()
+{
+  int soffset, toffset;
+  int i, j;
+
+
+  // i = t1.ver; j = t2.ver;
+  for (i = 0; i < 12; i++) {
+    for (j = 0; j < 12; j++) {
+      bondtbl[i][j] = (j & 3) + (((i & 12) + (j & 12)) % 12);
+    }
+  }
+
+
+  // i = t1.ver; j = t2.ver
+  for (i = 0; i < 12; i++) {
+    for (j = 0; j < 12; j++) {
+      fsymtbl[i][j] = (j + 12 - (i & 12)) % 12;
+    }
+  }
+
+
+  for (i = 0; i < 12; i++) {
+    facepivot1[i] = (esymtbl[i] & 3);
+  }
+
+  for (i = 0; i < 12; i++) {
+    for (j = 0; j < 12; j++) {
+      facepivot2[i][j] = fsymtbl[esymtbl[i]][j];
+    }
+  }
+
+  for (i = 0; i < 12; i++) {
+    enexttbl[i] = (i + 4) % 12;
+    eprevtbl[i] = (i + 8) % 12;
+  }
+
+  for (i = 0; i < 12; i++) {
+    enextesymtbl[i] = esymtbl[enexttbl[i]];
+    eprevesymtbl[i] = esymtbl[eprevtbl[i]];
+  }
+
+  for (i = 0; i < 12; i++) {
+    eorgoppotbl [i] = eprevtbl[esymtbl[enexttbl[i]]];
+    edestoppotbl[i] = enexttbl[esymtbl[eprevtbl[i]]];
+  }
+
+  // i = t.ver, j = s.shver
+  for (i = 0; i < 12; i++) {
+    for (j = 0; j < 6; j++) {
+      if ((j & 1) == 0) {
+        soffset = (6 - ((i & 12) >> 1)) % 6;
+        toffset = (12 - ((j & 6) << 1)) % 12;
+      } else {
+        soffset = (i & 12) >> 1;
+        toffset = (j & 6) << 1;
+      }
+      tsbondtbl[i][j] = (j & 1) + (((j & 6) + soffset) % 6);
+      stbondtbl[i][j] = (i & 3) + (((i & 12) + toffset) % 12);
+    }
+  }
+
+
+  // i = t.ver, j = s.shver
+  for (i = 0; i < 12; i++) {
+    for (j = 0; j < 6; j++) {
+      if ((j & 1) == 0) {
+        soffset = (i & 12) >> 1;
+        toffset = (j & 6) << 1;
+      } else {
+        soffset = (6 - ((i & 12) >> 1)) % 6;
+        toffset = (12 - ((j & 6) << 1)) % 12;
+      }
+      tspivottbl[i][j] = (j & 1) + (((j & 6) + soffset) % 6);
+      stpivottbl[i][j] = (i & 3) + (((i & 12) + toffset) % 12);
+    }
+  }
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// restart()    Deallocate all objects in this pool.                         //
+//                                                                           //
+// The pool returns to a fresh state, like after it was initialized, except  //
+// that no memory is freed to the operating system.  Rather, the previously  //
+// allocated blocks are ready to be used.                                    //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::arraypool::restart()
+{
+  objects = 0l;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// poolinit()    Initialize an arraypool for allocation of objects.          //
+//                                                                           //
+// Before the pool may be used, it must be initialized by this procedure.    //
+// After initialization, memory can be allocated and freed in this pool.     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::arraypool::poolinit(int sizeofobject, int log2objperblk)
+{
+  // Each object must be at least one byte long.
+  objectbytes = sizeofobject > 1 ? sizeofobject : 1;
+
+  log2objectsperblock = log2objperblk;
+  // Compute the number of objects in each block.
+  objectsperblock = ((int) 1) << log2objectsperblock;
+  objectsperblockmark = objectsperblock - 1;
+
+  // No memory has been allocated.
+  totalmemory = 0l;
+  // The top array has not been allocated yet.
+  toparray = (char **) NULL;
+  toparraylen = 0;
+
+  // Ready all indices to be allocated.
+  restart();
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// arraypool()    The constructor and destructor.                            //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+tetgenmesh::arraypool::arraypool(int sizeofobject, int log2objperblk)
+{
+  poolinit(sizeofobject, log2objperblk);
+}
+
+tetgenmesh::arraypool::~arraypool()
+{
+  int i;
+
+  // Has anything been allocated at all?
+  if (toparray != (char **) NULL) {
+    // Walk through the top array.
+    for (i = 0; i < toparraylen; i++) {
+      // Check every pointer; NULLs may be scattered randomly.
+      if (toparray[i] != (char *) NULL) {
+        // Free an allocated block.
+        free((void *) toparray[i]);
+      }
+    }
+    // Free the top array.
+    free((void *) toparray);
+  }
+
+  // The top array is no longer allocated.
+  toparray = (char **) NULL;
+  toparraylen = 0;
+  objects = 0;
+  totalmemory = 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// getblock()    Return (and perhaps create) the block containing the object //
+//               with a given index.                                         //
+//                                                                           //
+// This function takes care of allocating or resizing the top array if nece- //
+// ssary, and of allocating the block if it hasn't yet been allocated.       //
+//                                                                           //
+// Return a pointer to the beginning of the block (NOT the object).          //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+char* tetgenmesh::arraypool::getblock(int objectindex)
+{
+  char **newarray;
+  char *block;
+  int newsize;
+  int topindex;
+  int i;
+
+  // Compute the index in the top array (upper bits).
+  topindex = objectindex >> log2objectsperblock;
+  // Does the top array need to be allocated or resized?
+  if (toparray == (char **) NULL) {
+    // Allocate the top array big enough to hold 'topindex', and NULL out
+    //   its contents.
+    newsize = topindex + 128;
+    toparray = (char **) malloc((size_t) (newsize * sizeof(char *)));
+    toparraylen = newsize;
+    for (i = 0; i < newsize; i++) {
+      toparray[i] = (char *) NULL;
+    }
+    // Account for the memory.
+    totalmemory = newsize * (uintptr_t) sizeof(char *);
+  } else if (topindex >= toparraylen) {
+    // Resize the top array, making sure it holds 'topindex'.
+    newsize = 3 * toparraylen;
+    if (topindex >= newsize) {
+      newsize = topindex + 128;
+    }
+    // Allocate the new array, copy the contents, NULL out the rest, and
+    //   free the old array.
+    newarray = (char **) malloc((size_t) (newsize * sizeof(char *)));
+    for (i = 0; i < toparraylen; i++) {
+      newarray[i] = toparray[i];
+    }
+    for (i = toparraylen; i < newsize; i++) {
+      newarray[i] = (char *) NULL;
+    }
+    free(toparray);
+    // Account for the memory.
+    totalmemory += (newsize - toparraylen) * sizeof(char *);
+    toparray = newarray;
+    toparraylen = newsize;
+  }
+
+  // Find the block, or learn that it hasn't been allocated yet.
+  block = toparray[topindex];
+  if (block == (char *) NULL) {
+    // Allocate a block at this index.
+    block = (char *) malloc((size_t) (objectsperblock * objectbytes));
+    toparray[topindex] = block;
+    // Account for the memory.
+    totalmemory += objectsperblock * objectbytes;
+  }
+
+  // Return a pointer to the block.
+  return block;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// lookup()    Return the pointer to the object with a given index, or NULL  //
+//             if the object's block doesn't exist yet.                      //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void* tetgenmesh::arraypool::lookup(int objectindex)
+{
+  char *block;
+  int topindex;
+
+  // Has the top array been allocated yet?
+  if (toparray == (char **) NULL) {
+    return (void *) NULL;
+  }
+
+  // Compute the index in the top array (upper bits).
+  topindex = objectindex >> log2objectsperblock;
+  // Does the top index fit in the top array?
+  if (topindex >= toparraylen) {
+    return (void *) NULL;
+  }
+
+  // Find the block, or learn that it hasn't been allocated yet.
+  block = toparray[topindex];
+  if (block == (char *) NULL) {
+    return (void *) NULL;
+  }
+
+  // Compute a pointer to the object with the given index.  Note that
+  //   'objectsperblock' is a power of two, so the & operation is a bit mask
+  //   that preserves the lower bits.
+  return (void *)(block + (objectindex & (objectsperblock - 1)) * objectbytes);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// newindex()    Allocate space for a fresh object from the pool.            //
+//                                                                           //
+// 'newptr' returns a pointer to the new object (it must not be a NULL).     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::arraypool::newindex(void **newptr)
+{
+  // Allocate an object at index 'firstvirgin'.
+  int newindex = objects;
+  *newptr = (void *) (getblock(objects) +
+    (objects & (objectsperblock - 1)) * objectbytes);
+  objects++;
+
+  return newindex;
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// memorypool()   The constructors of memorypool.                            //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+tetgenmesh::memorypool::memorypool()
+{
+  firstblock = nowblock = (void **) NULL;
+  nextitem = (void *) NULL;
+  deaditemstack = (void *) NULL;
+  pathblock = (void **) NULL;
+  pathitem = (void *) NULL;
+  alignbytes = 0;
+  itembytes = itemwords = 0;
+  itemsperblock = 0;
+  items = maxitems = 0l;
+  unallocateditems = 0;
+  pathitemsleft = 0;
+}
+
+tetgenmesh::memorypool::memorypool(int bytecount, int itemcount, int wsize, 
+                                   int alignment)
+{
+  poolinit(bytecount, itemcount, wsize, alignment);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// ~memorypool()   Free to the operating system all memory taken by a pool.  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+tetgenmesh::memorypool::~memorypool()
+{
+  while (firstblock != (void **) NULL) {
+    nowblock = (void **) *(firstblock);
+    free(firstblock);
+    firstblock = nowblock;
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// poolinit()    Initialize a pool of memory for allocation of items.        //
+//                                                                           //
+// A `pool' is created whose records have size at least `bytecount'.  Items  //
+// will be allocated in `itemcount'-item blocks.  Each item is assumed to be //
+// a collection of words, and either pointers or floating-point values are   //
+// assumed to be the "primary" word type.  (The "primary" word type is used  //
+// to determine alignment of items.)  If `alignment' isn't zero, all items   //
+// will be `alignment'-byte aligned in memory.  `alignment' must be either a //
+// multiple or a factor of the primary word size;  powers of two are safe.   //
+// `alignment' is normally used to create a few unused bits at the bottom of //
+// each item's pointer, in which information may be stored.                  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::memorypool::poolinit(int bytecount,int itemcount,int wordsize,
+                                      int alignment)
+{
+  // Find the proper alignment, which must be at least as large as:
+  //   - The parameter `alignment'.
+  //   - The primary word type, to avoid unaligned accesses.
+  //   - sizeof(void *), so the stack of dead items can be maintained
+  //       without unaligned accesses.
+  if (alignment > wordsize) {
+    alignbytes = alignment;
+  } else {
+    alignbytes = wordsize;
+  }
+  if ((int) sizeof(void *) > alignbytes) {
+    alignbytes = (int) sizeof(void *);
+  }
+  itemwords = ((bytecount + alignbytes - 1) /  alignbytes)
+            * (alignbytes / wordsize);
+  itembytes = itemwords * wordsize;
+  itemsperblock = itemcount;
+
+  // Allocate a block of items.  Space for `itemsperblock' items and one
+  //   pointer (to point to the next block) are allocated, as well as space
+  //   to ensure alignment of the items. 
+  firstblock = (void **) malloc(itemsperblock * itembytes + sizeof(void *)
+                                + alignbytes); 
+  if (firstblock == (void **) NULL) {
+    terminatetetgen(NULL, 1);
+  }
+  // Set the next block pointer to NULL.
+  *(firstblock) = (void *) NULL;
+  restart();
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// restart()   Deallocate all items in this pool.                            //
+//                                                                           //
+// The pool is returned to its starting state, except that no memory is      //
+// freed to the operating system.  Rather, the previously allocated blocks   //
+// are ready to be reused.                                                   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::memorypool::restart()
+{
+  uintptr_t alignptr;
+
+  items = 0;
+  maxitems = 0;
+
+  // Set the currently active block.
+  nowblock = firstblock;
+  // Find the first item in the pool.  Increment by the size of (void *).
+  alignptr = (uintptr_t) (nowblock + 1);
+  // Align the item on an `alignbytes'-byte boundary.
+  nextitem = (void *)
+    (alignptr + (uintptr_t) alignbytes -
+     (alignptr % (uintptr_t) alignbytes));
+  // There are lots of unallocated items left in this block.
+  unallocateditems = itemsperblock;
+  // The stack of deallocated items is empty.
+  deaditemstack = (void *) NULL;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// alloc()   Allocate space for an item.                                     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void* tetgenmesh::memorypool::alloc()
+{
+  void *newitem;
+  void **newblock;
+  uintptr_t alignptr;
+
+  // First check the linked list of dead items.  If the list is not 
+  //   empty, allocate an item from the list rather than a fresh one.
+  if (deaditemstack != (void *) NULL) {
+    newitem = deaditemstack;                     // Take first item in list.
+    deaditemstack = * (void **) deaditemstack;
+  } else {
+    // Check if there are any free items left in the current block.
+    if (unallocateditems == 0) {
+      // Check if another block must be allocated.
+      if (*nowblock == (void *) NULL) {
+        // Allocate a new block of items, pointed to by the previous block.
+        newblock = (void **) malloc(itemsperblock * itembytes + sizeof(void *) 
+                                    + alignbytes);
+        if (newblock == (void **) NULL) {
+          terminatetetgen(NULL, 1);
+        }
+        *nowblock = (void *) newblock;
+        // The next block pointer is NULL.
+        *newblock = (void *) NULL;
+      }
+      // Move to the new block.
+      nowblock = (void **) *nowblock;
+      // Find the first item in the block.
+      //   Increment by the size of (void *).
+      alignptr = (uintptr_t) (nowblock + 1);
+      // Align the item on an `alignbytes'-byte boundary.
+      nextitem = (void *)
+        (alignptr + (uintptr_t) alignbytes -
+         (alignptr % (uintptr_t) alignbytes));
+      // There are lots of unallocated items left in this block.
+      unallocateditems = itemsperblock;
+    }
+    // Allocate a new item.
+    newitem = nextitem;
+    // Advance `nextitem' pointer to next free item in block.
+    nextitem = (void *) ((uintptr_t) nextitem + itembytes);
+    unallocateditems--;
+    maxitems++;
+  }
+  items++;
+  return newitem;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// dealloc()   Deallocate space for an item.                                 //
+//                                                                           //
+// The deallocated space is stored in a queue for later reuse.               //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::memorypool::dealloc(void *dyingitem)
+{
+  // Push freshly killed item onto stack.
+  *((void **) dyingitem) = deaditemstack;
+  deaditemstack = dyingitem;
+  items--;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// traversalinit()   Prepare to traverse the entire list of items.           //
+//                                                                           //
+// This routine is used in conjunction with traverse().                      //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::memorypool::traversalinit()
+{
+  uintptr_t alignptr;
+
+  // Begin the traversal in the first block.
+  pathblock = firstblock;
+  // Find the first item in the block.  Increment by the size of (void *).
+  alignptr = (uintptr_t) (pathblock + 1);
+  // Align with item on an `alignbytes'-byte boundary.
+  pathitem = (void *)
+    (alignptr + (uintptr_t) alignbytes -
+     (alignptr % (uintptr_t) alignbytes));
+  // Set the number of items left in the current block.
+  pathitemsleft = itemsperblock;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// traverse()   Find the next item in the list.                              //
+//                                                                           //
+// This routine is used in conjunction with traversalinit().  Be forewarned  //
+// that this routine successively returns all items in the list, including   //
+// deallocated ones on the deaditemqueue. It's up to you to figure out which //
+// ones are actually dead.  It can usually be done more space-efficiently by //
+// a routine that knows something about the structure of the item.           //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void* tetgenmesh::memorypool::traverse()
+{
+  void *newitem;
+  uintptr_t alignptr;
+
+  // Stop upon exhausting the list of items.
+  if (pathitem == nextitem) {
+    return (void *) NULL;
+  }
+  // Check whether any untraversed items remain in the current block.
+  if (pathitemsleft == 0) {
+    // Find the next block.
+    pathblock = (void **) *pathblock;
+    // Find the first item in the block.  Increment by the size of (void *).
+    alignptr = (uintptr_t) (pathblock + 1);
+    // Align with item on an `alignbytes'-byte boundary.
+    pathitem = (void *)
+      (alignptr + (uintptr_t) alignbytes -
+       (alignptr % (uintptr_t) alignbytes));
+    // Set the number of items left in the current block.
+    pathitemsleft = itemsperblock;
+  }
+  newitem = pathitem;
+  // Find the next item in the block.
+  pathitem = (void *) ((uintptr_t) pathitem + itembytes);
+  pathitemsleft--;
+  return newitem;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// makeindex2pointmap()    Create a map from index to vertices.              //
+//                                                                           //
+// 'idx2verlist' returns the created map.  Traverse all vertices, a pointer  //
+// to each vertex is set into the array.  The pointer to the first vertex is //
+// saved in 'idx2verlist[in->firstnumber]'.                                  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::makeindex2pointmap(point*& idx2verlist)
+{
+  point pointloop;
+  int idx;
+
+  if (b->verbose > 1) {
+    printf("  Constructing mapping from indices to points.\n");
+  }
+
+  idx2verlist = new point[points->items + 1];
+
+  points->traversalinit();
+  pointloop = pointtraverse();
+  idx =  in->firstnumber;
+  while (pointloop != (point) NULL) {
+    idx2verlist[idx++] = pointloop;
+    pointloop = pointtraverse();
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// makesubfacemap()    Create a map from vertex to subfaces incident at it.  //
+//                                                                           //
+// The map is returned in two arrays 'idx2faclist' and 'facperverlist'.  All //
+// subfaces incident at i-th vertex (i is counted from 0) are found in the   //
+// array facperverlist[j], where idx2faclist[i] <= j < idx2faclist[i + 1].   //
+// Each entry in facperverlist[j] is a subface whose origin is the vertex.   //
+//                                                                           //
+// NOTE: These two arrays will be created inside this routine, don't forget  //
+// to free them after using.                                                 //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::makepoint2submap(memorypool* pool, int*& idx2faclist,
+                                  face*& facperverlist)
+{
+  face shloop;
+  int i, j, k;
+
+  if (b->verbose > 1) {
+    printf("  Making a map from points to subfaces.\n");
+  }
+
+  // Initialize 'idx2faclist'.
+  idx2faclist = new int[points->items + 1];
+  for (i = 0; i < points->items + 1; i++) idx2faclist[i] = 0;
+
+  // Loop all subfaces, counter the number of subfaces incident at a vertex.
+  pool->traversalinit();
+  shloop.sh = shellfacetraverse(pool);
+  while (shloop.sh != (shellface *) NULL) {
+    // Increment the number of incident subfaces for each vertex.
+    j = pointmark((point) shloop.sh[3]) - in->firstnumber;
+    idx2faclist[j]++;
+    j = pointmark((point) shloop.sh[4]) - in->firstnumber;
+    idx2faclist[j]++;
+    // Skip the third corner if it is a segment.
+    if (shloop.sh[5] != NULL) {
+      j = pointmark((point) shloop.sh[5]) - in->firstnumber;
+      idx2faclist[j]++;
+    }
+    shloop.sh = shellfacetraverse(pool);
+  }
+
+  // Calculate the total length of array 'facperverlist'.
+  j = idx2faclist[0];
+  idx2faclist[0] = 0;  // Array starts from 0 element.
+  for (i = 0; i < points->items; i++) {
+    k = idx2faclist[i + 1];
+    idx2faclist[i + 1] = idx2faclist[i] + j;
+    j = k;
+  }
+
+  // The total length is in the last unit of idx2faclist.
+  facperverlist = new face[idx2faclist[i]];
+
+  // Loop all subfaces again, remember the subfaces at each vertex.
+  pool->traversalinit();
+  shloop.sh = shellfacetraverse(pool);
+  while (shloop.sh != (shellface *) NULL) {
+    j = pointmark((point) shloop.sh[3]) - in->firstnumber;
+    shloop.shver = 0; // save the origin.
+    facperverlist[idx2faclist[j]] = shloop;
+    idx2faclist[j]++;
+    // Is it a subface or a subsegment?
+    if (shloop.sh[5] != NULL) {
+      j = pointmark((point) shloop.sh[4]) - in->firstnumber;
+      shloop.shver = 2; // save the origin.
+      facperverlist[idx2faclist[j]] = shloop;
+      idx2faclist[j]++;
+      j = pointmark((point) shloop.sh[5]) - in->firstnumber;
+      shloop.shver = 4; // save the origin.
+      facperverlist[idx2faclist[j]] = shloop;
+      idx2faclist[j]++;
+    } else {
+      j = pointmark((point) shloop.sh[4]) - in->firstnumber;
+      shloop.shver = 1; // save the origin.
+      facperverlist[idx2faclist[j]] = shloop;
+      idx2faclist[j]++;
+    }
+    shloop.sh = shellfacetraverse(pool);
+  }
+
+  // Contents in 'idx2faclist' are shifted, now shift them back.
+  for (i = points->items - 1; i >= 0; i--) {
+    idx2faclist[i + 1] = idx2faclist[i];
+  }
+  idx2faclist[0] = 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// tetrahedrondealloc()    Deallocate space for a tet., marking it dead.     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::tetrahedrondealloc(tetrahedron *dyingtetrahedron)
+{
+  // Set tetrahedron's vertices to NULL. This makes it possible to detect
+  //   dead tetrahedra when traversing the list of all tetrahedra.
+  dyingtetrahedron[4] = (tetrahedron) NULL;
+
+  // Dealloc the space to subfaces/subsegments.
+  if (dyingtetrahedron[8] != NULL) {
+    tet2segpool->dealloc((shellface *) dyingtetrahedron[8]);
+  }
+  if (dyingtetrahedron[9] != NULL) {
+    tet2subpool->dealloc((shellface *) dyingtetrahedron[9]);
+  }
+
+  tetrahedrons->dealloc((void *) dyingtetrahedron);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// tetrahedrontraverse()    Traverse the tetrahedra, skipping dead ones.     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+tetgenmesh::tetrahedron* tetgenmesh::tetrahedrontraverse()
+{
+  tetrahedron *newtetrahedron;
+
+  do {
+    newtetrahedron = (tetrahedron *) tetrahedrons->traverse();
+    if (newtetrahedron == (tetrahedron *) NULL) {
+      return (tetrahedron *) NULL;
+    }
+  } while ((newtetrahedron[4] == (tetrahedron) NULL) ||
+           ((point) newtetrahedron[7] == dummypoint));
+  return newtetrahedron;
+}
+
+tetgenmesh::tetrahedron* tetgenmesh::alltetrahedrontraverse()
+{
+  tetrahedron *newtetrahedron;
+
+  do {
+    newtetrahedron = (tetrahedron *) tetrahedrons->traverse();
+    if (newtetrahedron == (tetrahedron *) NULL) {
+      return (tetrahedron *) NULL;
+    }
+  } while (newtetrahedron[4] == (tetrahedron) NULL); // Skip dead ones.
+  return newtetrahedron;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// shellfacedealloc()    Deallocate space for a shellface, marking it dead.  //
+//                       Used both for dealloc a subface and subsegment.     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::shellfacedealloc(memorypool *pool, shellface *dyingsh)
+{
+  // Set shellface's vertices to NULL. This makes it possible to detect dead
+  //   shellfaces when traversing the list of all shellfaces.
+  dyingsh[3] = (shellface) NULL;
+  pool->dealloc((void *) dyingsh);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// shellfacetraverse()    Traverse the subfaces, skipping dead ones. Used    //
+//                        for both subfaces and subsegments pool traverse.   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+tetgenmesh::shellface* tetgenmesh::shellfacetraverse(memorypool *pool)
+{
+  shellface *newshellface;
+
+  do {
+    newshellface = (shellface *) pool->traverse();
+    if (newshellface == (shellface *) NULL) {
+      return (shellface *) NULL;
+    }
+  } while (newshellface[3] == (shellface) NULL);          // Skip dead ones.
+  return newshellface;
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// pointdealloc()    Deallocate space for a point, marking it dead.          //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::pointdealloc(point dyingpoint)
+{
+  // Mark the point as dead. This  makes it possible to detect dead points
+  //   when traversing the list of all points.
+  setpointtype(dyingpoint, DEADVERTEX);
+  points->dealloc((void *) dyingpoint);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// pointtraverse()    Traverse the points, skipping dead ones.               //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+tetgenmesh::point tetgenmesh::pointtraverse()
+{
+  point newpoint;
+
+  do {
+    newpoint = (point) points->traverse();
+    if (newpoint == (point) NULL) {
+      return (point) NULL;
+    }
+  } while (pointtype(newpoint) == DEADVERTEX);            // Skip dead ones.
+  return newpoint;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// maketetrahedron()    Create a new tetrahedron.                            //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::maketetrahedron(triface *newtet)
+{
+  newtet->tet = (tetrahedron *) tetrahedrons->alloc();
+
+  // Initialize the four adjoining tetrahedra to be "outer space".
+  newtet->tet[0] = NULL;
+  newtet->tet[1] = NULL;
+  newtet->tet[2] = NULL;
+  newtet->tet[3] = NULL;
+  // Four NULL vertices.
+  newtet->tet[4] = NULL;
+  newtet->tet[5] = NULL;
+  newtet->tet[6] = NULL;
+  newtet->tet[7] = NULL;
+  // No attached segments and subfaces yet.
+  newtet->tet[8] = NULL; 
+  newtet->tet[9] = NULL; 
+  // Initialize the marker (clear all flags).
+  setelemmarker(newtet->tet, 0);
+  for (int i = 0; i < numelemattrib; i++) {
+    setelemattribute(newtet->tet, i, 0.0);
+  }
+  if (b->varvolume) {
+    setvolumebound(newtet->tet, -1.0);
+  }
+
+  // Initialize the version to be Zero.
+  newtet->ver = 11;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// makeshellface()    Create a new shellface with version zero. Used for     //
+//                    both subfaces and subsegments.                         //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::makeshellface(memorypool *pool, face *newface)
+{
+  newface->sh = (shellface *) pool->alloc();
+
+  // No adjointing subfaces.
+  newface->sh[0] = NULL;
+  newface->sh[1] = NULL;
+  newface->sh[2] = NULL;
+  // Three NULL vertices.
+  newface->sh[3] = NULL;
+  newface->sh[4] = NULL;
+  newface->sh[5] = NULL;
+  // No adjoining subsegments.
+  newface->sh[6] = NULL;
+  newface->sh[7] = NULL;
+  newface->sh[8] = NULL;
+  // No adjoining tetrahedra.
+  newface->sh[9] = NULL;
+  newface->sh[10] = NULL;
+  if (checkconstraints) {
+    // Initialize the maximum area bound.
+    setareabound(*newface, 0.0);
+  }
+  // Set the boundary marker to zero.
+  setshellmark(*newface, 0);
+  // Clear the infection and marktest bits.
+  ((int *) (newface->sh))[shmarkindex + 1] = 0;
+  if (useinsertradius) {
+    setfacetindex(*newface, 0);
+  }
+
+  newface->shver = 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// makepoint()    Create a new point.                                        //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::makepoint(point* pnewpoint, enum verttype vtype)
+{
+  int i;
+
+  *pnewpoint = (point) points->alloc();
+
+  // Initialize the point attributes.
+  for (i = 0; i < numpointattrib; i++) {
+    (*pnewpoint)[3 + i] = 0.0;
+  }
+  // Initialize the metric tensor.
+  for (i = 0; i < sizeoftensor; i++) {
+    (*pnewpoint)[pointmtrindex + i] = 0.0;
+  }
+  setpoint2tet(*pnewpoint, NULL);
+  setpoint2ppt(*pnewpoint, NULL);
+  if (b->plc || b->refine) {
+    // Initialize the point-to-simplex field.
+    setpoint2sh(*pnewpoint, NULL);
+    if (b->metric && (bgm != NULL)) {
+      setpoint2bgmtet(*pnewpoint, NULL);
+    }
+  }
+  // Initialize the point marker (starting from in->firstnumber).
+  setpointmark(*pnewpoint, (int) (points->items) - (!in->firstnumber));
+  // Clear all flags.
+  ((int *) (*pnewpoint))[pointmarkindex + 1] = 0;
+  // Initialize (set) the point type. 
+  setpointtype(*pnewpoint, vtype);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// initializepools()    Calculate the sizes of the point, tetrahedron, and   //
+//                      subface. Initialize their memory pools.              //
+//                                                                           //
+// This routine also computes the indices 'pointmarkindex', 'point2simindex',//
+// 'point2pbcptindex', 'elemattribindex', and 'volumeboundindex'.  They are  //
+// used to find values within each point and tetrahedron, respectively.      //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::initializepools()
+{
+  int pointsize = 0, elesize = 0, shsize = 0;
+  int i;
+
+  if (b->verbose) {
+    printf("  Initializing memorypools.\n");
+    printf("  tetrahedron per block: %d.\n", b->tetrahedraperblock);
+  }
+
+  inittables();
+
+  // There are three input point lists available, which are in, addin,
+  //   and bgm->in. These point lists may have different number of 
+  //   attributes. Decide the maximum number.
+  numpointattrib = in->numberofpointattributes;
+  if (bgm != NULL) {
+    if (bgm->in->numberofpointattributes > numpointattrib) {
+      numpointattrib = bgm->in->numberofpointattributes;
+    }
+  }
+  if (addin != NULL) {
+    if (addin->numberofpointattributes > numpointattrib) {
+      numpointattrib = addin->numberofpointattributes;
+    }
+  }
+  if (b->weighted || b->flipinsert) { // -w or -L.
+    // The internal number of point attribute needs to be at least 1
+    //   (for storing point weights).
+    if (numpointattrib == 0) {    
+      numpointattrib = 1;
+    }
+  }
+
+  // Default varconstraint = 0;
+  if (in->segmentconstraintlist || in->facetconstraintlist) {
+    checkconstraints = 1;
+  }
+  if (b->plc || b->refine) {
+    // Save the insertion radius for Steiner points if boundaries
+    //   are allowed be split.
+    if (!b->nobisect || checkconstraints) {
+      useinsertradius = 1;
+    }
+  }
+
+  // The index within each point at which its metric tensor is found. 
+  // Each vertex has three coordinates.
+  if (b->psc) {
+    // '-s' option (PSC), the u,v coordinates are provided.
+    pointmtrindex = 5 + numpointattrib;
+    // The index within each point at which its u, v coordinates are found.
+    // Comment: They are saved after the list of point attributes.
+    pointparamindex = pointmtrindex - 2;
+  } else {
+    pointmtrindex = 3 + numpointattrib;
+  }
+  // For '-m' option. A tensor field is provided (*.mtr or *.b.mtr file).
+  if (b->metric) {
+    // Decide the size (1, 3, or 6) of the metric tensor.
+    if (bgm != (tetgenmesh *) NULL) {
+      // A background mesh is allocated. It may not exist though.
+      sizeoftensor = (bgm->in != (tetgenio *) NULL) ? 
+        bgm->in->numberofpointmtrs : in->numberofpointmtrs;
+    } else {
+      // No given background mesh - Itself is a background mesh.
+      sizeoftensor = in->numberofpointmtrs;
+    }
+    // Make sure sizeoftensor is at least 1.
+    sizeoftensor = (sizeoftensor > 0) ? sizeoftensor : 1;
+  } else {
+    // For '-q' option. Make sure to have space for saving a scalar value.
+    sizeoftensor = b->quality ? 1 : 0;
+  }
+  if (useinsertradius) {
+    // Increase a space (REAL) for saving point insertion radius, it is
+    //   saved directly after the metric. 
+    sizeoftensor++;
+  }
+  pointinsradiusindex = pointmtrindex + sizeoftensor - 1;
+  // The index within each point at which an element pointer is found, where
+  //   the index is measured in pointers. Ensure the index is aligned to a
+  //   sizeof(tetrahedron)-byte address.
+  point2simindex = ((pointmtrindex + sizeoftensor) * sizeof(REAL)
+                 + sizeof(tetrahedron) - 1) / sizeof(tetrahedron);
+  if (b->plc || b->refine || b->voroout) {
+    // Increase the point size by three pointers, which are:
+    //   - a pointer to a tet, read by point2tet();
+    //   - a pointer to a parent point, read by point2ppt()).
+    //   - a pointer to a subface or segment, read by point2sh();
+    if (b->metric && (bgm != (tetgenmesh *) NULL)) {
+      // Increase one pointer into the background mesh, point2bgmtet().
+      pointsize = (point2simindex + 4) * sizeof(tetrahedron);
+    } else {
+      pointsize = (point2simindex + 3) * sizeof(tetrahedron);
+    }
+  } else {
+    // Increase the point size by two pointer, which are:
+    //   - a pointer to a tet, read by point2tet();
+    //   - a pointer to a parent point, read by point2ppt()). -- Used by btree.
+    pointsize = (point2simindex + 2) * sizeof(tetrahedron);
+  }
+  // The index within each point at which the boundary marker is found,
+  //   Ensure the point marker is aligned to a sizeof(int)-byte address.
+  pointmarkindex = (pointsize + sizeof(int) - 1) / sizeof(int);
+  // Now point size is the ints (indicated by pointmarkindex) plus:
+  //   - an integer for boundary marker;
+  //   - an integer for vertex type;
+  //   - an integer for geometry tag (optional, -s option).
+  pointsize = (pointmarkindex + 2 + (b->psc ? 1 : 0)) * sizeof(tetrahedron);
+
+  // Initialize the pool of vertices.
+  points = new memorypool(pointsize, b->vertexperblock, sizeof(REAL), 0);
+
+  if (b->verbose) {
+    printf("  Size of a point: %d bytes.\n", points->itembytes);
+  }
+
+  // Initialize the infinite vertex.
+  dummypoint = (point) new char[pointsize];
+  // Initialize all fields of this point.
+  dummypoint[0] = 0.0;
+  dummypoint[1] = 0.0;
+  dummypoint[2] = 0.0;
+  for (i = 0; i < numpointattrib; i++) {
+    dummypoint[3 + i] = 0.0;
+  }
+  // Initialize the metric tensor.
+  for (i = 0; i < sizeoftensor; i++) {
+    dummypoint[pointmtrindex + i] = 0.0;
+  }
+  setpoint2tet(dummypoint, NULL);
+  setpoint2ppt(dummypoint, NULL);
+  if (b->plc || b->psc || b->refine) {
+    // Initialize the point-to-simplex field.
+    setpoint2sh(dummypoint, NULL);
+    if (b->metric && (bgm != NULL)) {
+      setpoint2bgmtet(dummypoint, NULL);
+    }
+  }
+  // Initialize the point marker (starting from in->firstnumber).
+  setpointmark(dummypoint, -1); // The unique marker for dummypoint.
+  // Clear all flags.
+  ((int *) (dummypoint))[pointmarkindex + 1] = 0;
+  // Initialize (set) the point type. 
+  setpointtype(dummypoint, UNUSEDVERTEX); // Does not matter.
+
+  // The number of bytes occupied by a tetrahedron is varying by the user-
+  //   specified options. The contents of the first 12 pointers are listed
+  //   in the following table:
+  //     [0]  |__ neighbor at f0 __|
+  //     [1]  |__ neighbor at f1 __|
+  //     [2]  |__ neighbor at f2 __|
+  //     [3]  |__ neighbor at f3 __|
+  //     [4]  |_____ vertex p0 ____|
+  //     [5]  |_____ vertex p1 ____|
+  //     [6]  |_____ vertex p2 ____|
+  //     [7]  |_____ vertex p3 ____|
+  //     [8]  |__ segments array __| (used by -p)
+  //     [9]  |__ subfaces array __| (used by -p)
+  //    [10]  |_____ reserved _____|
+  //    [11]  |___ elem marker ____| (used as an integer)
+
+  elesize = 12 * sizeof(tetrahedron); 
+
+  // The index to find the element markers. An integer containing varies
+  //   flags and element counter. 
+  if (!(sizeof(int) <= sizeof(tetrahedron)) ||
+      ((sizeof(tetrahedron) % sizeof(int)))) {
+    terminatetetgen(this, 2);
+  }
+  elemmarkerindex = (elesize - sizeof(tetrahedron)) / sizeof(int);
+
+  // The actual number of element attributes. Note that if the
+  //   `b->regionattrib' flag is set, an additional attribute will be added.
+  numelemattrib = in->numberoftetrahedronattributes + (b->regionattrib > 0);
+
+  // The index within each element at which its attributes are found, where
+  //   the index is measured in REALs. 
+  elemattribindex = (elesize + sizeof(REAL) - 1) / sizeof(REAL);
+  // The index within each element at which the maximum volume bound is
+  //   found, where the index is measured in REALs.
+  volumeboundindex = elemattribindex + numelemattrib;
+  // If element attributes or an constraint are needed, increase the number
+  //   of bytes occupied by an element.
+  if (b->varvolume) {
+    elesize = (volumeboundindex + 1) * sizeof(REAL);
+  } else if (numelemattrib > 0) {
+    elesize = volumeboundindex * sizeof(REAL);
+  }
+
+
+  // Having determined the memory size of an element, initialize the pool.
+  tetrahedrons = new memorypool(elesize, b->tetrahedraperblock, sizeof(void *),
+                                16);
+
+  if (b->verbose) {
+    printf("  Size of a tetrahedron: %d (%d) bytes.\n", elesize,
+           tetrahedrons->itembytes);
+  }
+
+  if (b->plc || b->refine) { // if (b->useshelles) {
+    // The number of bytes occupied by a subface.  The list of pointers
+    //   stored in a subface are: three to other subfaces, three to corners,
+    //   three to subsegments, two to tetrahedra.
+    shsize = 11 * sizeof(shellface);
+    // The index within each subface at which the maximum area bound is
+    //   found, where the index is measured in REALs.
+    areaboundindex = (shsize + sizeof(REAL) - 1) / sizeof(REAL);
+    // If -q switch is in use, increase the number of bytes occupied by
+    //   a subface for saving maximum area bound.
+    if (checkconstraints) { 
+      shsize = (areaboundindex + 1) * sizeof(REAL);
+    } else {
+      shsize = areaboundindex * sizeof(REAL);
+    }
+    // The index within subface at which the facet marker is found. Ensure
+    //   the marker is aligned to a sizeof(int)-byte address.
+    shmarkindex = (shsize + sizeof(int) - 1) / sizeof(int);
+    // Increase the number of bytes by two or three integers, one for facet
+    //   marker, one for shellface type and flags, and optionally one
+	//   for storing facet index (for mesh refinement).
+    shsize = (shmarkindex + 2 + useinsertradius) * sizeof(shellface);
+
+    // Initialize the pool of subfaces. Each subface record is eight-byte
+    //   aligned so it has room to store an edge version (from 0 to 5) in
+    //   the least three bits.
+    subfaces = new memorypool(shsize, b->shellfaceperblock, sizeof(void *), 8);
+
+    if (b->verbose) {
+      printf("  Size of a shellface: %d (%d) bytes.\n", shsize,
+             subfaces->itembytes);
+    }
+
+    // Initialize the pool of subsegments. The subsegment's record is same
+    //   with subface.
+    subsegs = new memorypool(shsize, b->shellfaceperblock, sizeof(void *), 8);
+
+    // Initialize the pool for tet-subseg connections.
+    tet2segpool = new memorypool(6 * sizeof(shellface), b->shellfaceperblock, 
+                                 sizeof(void *), 0);
+    // Initialize the pool for tet-subface connections.
+    tet2subpool = new memorypool(4 * sizeof(shellface), b->shellfaceperblock, 
+                                 sizeof(void *), 0);
+
+    // Initialize arraypools for segment & facet recovery.
+    subsegstack = new arraypool(sizeof(face), 10);
+    subfacstack = new arraypool(sizeof(face), 10);
+    subvertstack = new arraypool(sizeof(point), 8);
+
+    // Initialize arraypools for surface point insertion/deletion.
+    caveshlist = new arraypool(sizeof(face), 8);
+    caveshbdlist = new arraypool(sizeof(face), 8);
+    cavesegshlist = new arraypool(sizeof(face), 4);
+
+    cavetetshlist = new arraypool(sizeof(face), 8);
+    cavetetseglist = new arraypool(sizeof(face), 8);
+    caveencshlist = new arraypool(sizeof(face), 8);
+    caveencseglist = new arraypool(sizeof(face), 8);
+  }
+
+  // Initialize the pools for flips.
+  flippool = new memorypool(sizeof(badface), 1024, sizeof(void *), 0);
+  unflipqueue = new arraypool(sizeof(badface), 10);
+
+  // Initialize the arraypools for point insertion.
+  cavetetlist = new arraypool(sizeof(triface), 10);
+  cavebdrylist = new arraypool(sizeof(triface), 10);
+  caveoldtetlist = new arraypool(sizeof(triface), 10);
+  cavetetvertlist = new arraypool(sizeof(point), 10);
+}
+
+////                                                                       ////
+////                                                                       ////
+//// mempool_cxx //////////////////////////////////////////////////////////////
+
+//// geom_cxx /////////////////////////////////////////////////////////////////
+////                                                                       ////
+////                                                                       ////
+
+// PI is the ratio of a circle's circumference to its diameter.
+REAL tetgenmesh::PI = 3.14159265358979323846264338327950288419716939937510582;
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// insphere_s()    Insphere test with symbolic perturbation.                 //
+//                                                                           //
+// Given four points pa, pb, pc, and pd, test if the point pe lies inside or //
+// outside the circumscribed sphere of the four points.                      //
+//                                                                           //
+// Here we assume that the 3d orientation of the point sequence {pa, pb, pc, //
+// pd} is positive (NOT zero), i.e., pd lies above the plane passing through //
+// points pa, pb, and pc. Otherwise, the returned sign is flipped.           //
+//                                                                           //
+// Return a positive value (> 0) if pe lies inside, a negative value (< 0)   //
+// if pe lies outside the sphere, the returned value will not be zero.       //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+REAL tetgenmesh::insphere_s(REAL* pa, REAL* pb, REAL* pc, REAL* pd, REAL* pe)
+{
+  REAL sign;
+
+  sign = insphere(pa, pb, pc, pd, pe);
+  if (sign != 0.0) {
+    return sign;
+  }
+
+  // Symbolic perturbation.
+  point pt[5], swappt;
+  REAL oriA, oriB;
+  int swaps, count;
+  int n, i;
+
+  pt[0] = pa;
+  pt[1] = pb;
+  pt[2] = pc;
+  pt[3] = pd;
+  pt[4] = pe;
+  
+  // Sort the five points such that their indices are in the increasing
+  //   order. An optimized bubble sort algorithm is used, i.e., it has
+  //   the worst case O(n^2) runtime, but it is usually much faster.
+  swaps = 0; // Record the total number of swaps.
+  n = 5;
+  do {
+    count = 0;
+    n = n - 1;
+    for (i = 0; i < n; i++) {
+      if (pointmark(pt[i]) > pointmark(pt[i+1])) {
+        swappt = pt[i]; pt[i] = pt[i+1]; pt[i+1] = swappt;
+        count++;
+      }
+    }
+    swaps += count;
+  } while (count > 0); // Continue if some points are swapped.
+
+  oriA = orient3d(pt[1], pt[2], pt[3], pt[4]);
+  if (oriA != 0.0) {
+    // Flip the sign if there are odd number of swaps.
+    if ((swaps % 2) != 0) oriA = -oriA;
+    return oriA;
+  }
+  
+  oriB = -orient3d(pt[0], pt[2], pt[3], pt[4]);
+  if (oriB == 0.0) {
+    terminatetetgen(this, 2);
+  }
+  // Flip the sign if there are odd number of swaps.
+  if ((swaps % 2) != 0) oriB = -oriB;
+  return oriB;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// orient4d_s()    4d orientation test with symbolic perturbation.           //
+//                                                                           //
+// Given four lifted points pa', pb', pc', and pd' in R^4,test if the lifted //
+// point pe' in R^4 lies below or above the hyperplane passing through the   //
+// four points pa', pb', pc', and pd'.                                       //
+//                                                                           //
+// Here we assume that the 3d orientation of the point sequence {pa, pb, pc, //
+// pd} is positive (NOT zero), i.e., pd lies above the plane passing through //
+// the points pa, pb, and pc. Otherwise, the returned sign is flipped.       //
+//                                                                           //
+// Return a positive value (> 0) if pe' lies below, a negative value (< 0)   //
+// if pe' lies above the hyperplane, the returned value should not be zero.  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+REAL tetgenmesh::orient4d_s(REAL* pa, REAL* pb, REAL* pc, REAL* pd, REAL* pe,
+                            REAL aheight, REAL bheight, REAL cheight, 
+                            REAL dheight, REAL eheight)
+{
+  REAL sign;
+
+  sign = orient4d(pa, pb, pc, pd, pe, 
+                  aheight, bheight, cheight, dheight, eheight);
+  if (sign != 0.0) {
+    return sign;
+  }
+
+  // Symbolic perturbation.
+  point pt[5], swappt;
+  REAL oriA, oriB;
+  int swaps, count;
+  int n, i;
+
+  pt[0] = pa;
+  pt[1] = pb;
+  pt[2] = pc;
+  pt[3] = pd;
+  pt[4] = pe;
+  
+  // Sort the five points such that their indices are in the increasing
+  //   order. An optimized bubble sort algorithm is used, i.e., it has
+  //   the worst case O(n^2) runtime, but it is usually much faster.
+  swaps = 0; // Record the total number of swaps.
+  n = 5;
+  do {
+    count = 0;
+    n = n - 1;
+    for (i = 0; i < n; i++) {
+      if (pointmark(pt[i]) > pointmark(pt[i+1])) {
+        swappt = pt[i]; pt[i] = pt[i+1]; pt[i+1] = swappt;
+        count++;
+      }
+    }
+    swaps += count;
+  } while (count > 0); // Continue if some points are swapped.
+
+  oriA = orient3d(pt[1], pt[2], pt[3], pt[4]);
+  if (oriA != 0.0) {
+    // Flip the sign if there are odd number of swaps.
+    if ((swaps % 2) != 0) oriA = -oriA;
+    return oriA;
+  }
+  
+  oriB = -orient3d(pt[0], pt[2], pt[3], pt[4]);
+  if (oriB == 0.0) {
+    terminatetetgen(this, 2);
+  }
+  // Flip the sign if there are odd number of swaps.
+  if ((swaps % 2) != 0) oriB = -oriB;
+  return oriB;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// tri_edge_test()    Triangle-edge intersection test.                       //
+//                                                                           //
+// This routine takes a triangle T (with vertices A, B, C) and an edge E (P, //
+// Q) in 3D, and tests if they intersect each other.                         //
+//                                                                           //
+// If the point 'R' is not NULL, it lies strictly above the plane defined by //
+// A, B, C. It is used in test when T and E are coplanar.                    //
+//                                                                           //
+// If T and E intersect each other, they may intersect in different ways. If //
+// 'level' > 0, their intersection type will be reported 'types' and 'pos'.  //
+//                                                                           //
+// The return value indicates one of the following cases:                    //
+//   - 0, T and E are disjoint.                                              //
+//   - 1, T and E intersect each other.                                      //
+//   - 2, T and E are not coplanar. They intersect at a single point.        //
+//   - 4, T and E are coplanar. They intersect at a single point or a line   //
+//        segment (if types[1] != DISJOINT).                                 //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+#define SETVECTOR3(V, a0, a1, a2) (V)[0] = (a0); (V)[1] = (a1); (V)[2] = (a2)
+
+#define SWAP2(a0, a1, tmp) (tmp) = (a0); (a0) = (a1); (a1) = (tmp)
+
+int tetgenmesh::tri_edge_2d(point A, point B, point C, point P, point Q, 
+                            point R, int level, int *types, int *pos)
+{
+  point U[3], V[3];  // The permuted vectors of points.
+  int pu[3], pv[3];  // The original positions of points.
+  REAL abovept[3];
+  REAL sA, sB, sC;
+  REAL s1, s2, s3, s4;
+  int z1;
+
+  if (R == NULL) {
+    // Calculate a lift point.
+    if (1) {
+      REAL n[3], len;
+      // Calculate a lift point, saved in dummypoint.
+      facenormal(A, B, C, n, 1, NULL);
+      len = sqrt(dot(n, n));
+      if (len != 0) {
+        n[0] /= len;
+        n[1] /= len;
+        n[2] /= len;
+        len = distance(A, B);
+        len += distance(B, C);
+        len += distance(C, A);
+        len /= 3.0;
+        R = abovept; //dummypoint;
+        R[0] = A[0] + len * n[0];
+        R[1] = A[1] + len * n[1];
+        R[2] = A[2] + len * n[2];
+      } else {
+        // The triangle [A,B,C] is (nearly) degenerate, i.e., it is (close)
+        //   to a line.  We need a line-line intersection test.
+        // !!! A non-save return value.!!!
+        return 0;  // DISJOINT
+      }
+    }
+  }
+
+  // Test A's, B's, and C's orientations wrt plane PQR. 
+  sA = orient3d(P, Q, R, A);
+  sB = orient3d(P, Q, R, B);
+  sC = orient3d(P, Q, R, C);
+
+
+  if (sA < 0) {
+    if (sB < 0) {
+      if (sC < 0) { // (---).
+        return 0; 
+      } else {
+        if (sC > 0) { // (--+).
+          // All points are in the right positions.
+          SETVECTOR3(U, A, B, C);  // I3
+          SETVECTOR3(V, P, Q, R);  // I2
+          SETVECTOR3(pu, 0, 1, 2);
+          SETVECTOR3(pv, 0, 1, 2);
+          z1 = 0;
+        } else { // (--0).
+          SETVECTOR3(U, A, B, C);  // I3
+          SETVECTOR3(V, P, Q, R);  // I2
+          SETVECTOR3(pu, 0, 1, 2);
+          SETVECTOR3(pv, 0, 1, 2);
+          z1 = 1;
+        }
+      }
+    } else { 
+      if (sB > 0) {
+        if (sC < 0) { // (-+-).
+          SETVECTOR3(U, C, A, B);  // PT = ST
+          SETVECTOR3(V, P, Q, R);  // I2
+          SETVECTOR3(pu, 2, 0, 1);
+          SETVECTOR3(pv, 0, 1, 2);
+          z1 = 0;
+        } else {
+          if (sC > 0) { // (-++).
+            SETVECTOR3(U, B, C, A);  // PT = ST x ST
+            SETVECTOR3(V, Q, P, R);  // PL = SL
+            SETVECTOR3(pu, 1, 2, 0);
+            SETVECTOR3(pv, 1, 0, 2);
+            z1 = 0;
+          } else { // (-+0).
+            SETVECTOR3(U, C, A, B);  // PT = ST
+            SETVECTOR3(V, P, Q, R);  // I2
+            SETVECTOR3(pu, 2, 0, 1);
+            SETVECTOR3(pv, 0, 1, 2);
+            z1 = 2;
+          }
+        }
+      } else {
+        if (sC < 0) { // (-0-).
+          SETVECTOR3(U, C, A, B);  // PT = ST
+          SETVECTOR3(V, P, Q, R);  // I2
+          SETVECTOR3(pu, 2, 0, 1);
+          SETVECTOR3(pv, 0, 1, 2);
+          z1 = 1;
+        } else {
+          if (sC > 0) { // (-0+).
+            SETVECTOR3(U, B, C, A);  // PT = ST x ST
+            SETVECTOR3(V, Q, P, R);  // PL = SL
+            SETVECTOR3(pu, 1, 2, 0);
+            SETVECTOR3(pv, 1, 0, 2);
+            z1 = 2;
+          } else { // (-00).
+            SETVECTOR3(U, B, C, A);  // PT = ST x ST
+            SETVECTOR3(V, Q, P, R);  // PL = SL
+            SETVECTOR3(pu, 1, 2, 0);
+            SETVECTOR3(pv, 1, 0, 2);
+            z1 = 3; 
+          }
+        }
+      }
+    }
+  } else {
+    if (sA > 0) {
+      if (sB < 0) {
+        if (sC < 0) { // (+--).
+          SETVECTOR3(U, B, C, A);  // PT = ST x ST
+          SETVECTOR3(V, P, Q, R);  // I2
+          SETVECTOR3(pu, 1, 2, 0);
+          SETVECTOR3(pv, 0, 1, 2);
+          z1 = 0;
+        } else {
+          if (sC > 0) { // (+-+).
+            SETVECTOR3(U, C, A, B);  // PT = ST
+            SETVECTOR3(V, Q, P, R);  // PL = SL
+            SETVECTOR3(pu, 2, 0, 1);
+            SETVECTOR3(pv, 1, 0, 2);
+            z1 = 0;
+          } else { // (+-0).
+            SETVECTOR3(U, C, A, B);  // PT = ST
+            SETVECTOR3(V, Q, P, R);  // PL = SL
+            SETVECTOR3(pu, 2, 0, 1);
+            SETVECTOR3(pv, 1, 0, 2);
+            z1 = 2;
+          }
+        }
+      } else { 
+        if (sB > 0) {
+          if (sC < 0) { // (++-).
+            SETVECTOR3(U, A, B, C);  // I3
+            SETVECTOR3(V, Q, P, R);  // PL = SL
+            SETVECTOR3(pu, 0, 1, 2);
+            SETVECTOR3(pv, 1, 0, 2);
+            z1 = 0;
+          } else {
+            if (sC > 0) { // (+++).
+              return 0; 
+            } else { // (++0).
+              SETVECTOR3(U, A, B, C);  // I3
+              SETVECTOR3(V, Q, P, R);  // PL = SL
+              SETVECTOR3(pu, 0, 1, 2);
+              SETVECTOR3(pv, 1, 0, 2);
+              z1 = 1; 
+            }
+          }
+        } else { // (+0#)
+          if (sC < 0) { // (+0-).
+            SETVECTOR3(U, B, C, A);  // PT = ST x ST
+            SETVECTOR3(V, P, Q, R);  // I2
+            SETVECTOR3(pu, 1, 2, 0);
+            SETVECTOR3(pv, 0, 1, 2);
+            z1 = 2;
+          } else {
+            if (sC > 0) { // (+0+).
+              SETVECTOR3(U, C, A, B);  // PT = ST
+              SETVECTOR3(V, Q, P, R);  // PL = SL
+              SETVECTOR3(pu, 2, 0, 1);
+              SETVECTOR3(pv, 1, 0, 2);
+              z1 = 1;
+            } else { // (+00).
+              SETVECTOR3(U, B, C, A);  // PT = ST x ST
+              SETVECTOR3(V, P, Q, R);  // I2
+              SETVECTOR3(pu, 1, 2, 0);
+              SETVECTOR3(pv, 0, 1, 2);
+              z1 = 3; 
+            }
+          }
+        }
+      }
+    } else { 
+      if (sB < 0) {
+        if (sC < 0) { // (0--).
+          SETVECTOR3(U, B, C, A);  // PT = ST x ST
+          SETVECTOR3(V, P, Q, R);  // I2
+          SETVECTOR3(pu, 1, 2, 0);
+          SETVECTOR3(pv, 0, 1, 2);
+          z1 = 1;
+        } else {
+          if (sC > 0) { // (0-+).
+            SETVECTOR3(U, A, B, C);  // I3
+            SETVECTOR3(V, P, Q, R);  // I2
+            SETVECTOR3(pu, 0, 1, 2);
+            SETVECTOR3(pv, 0, 1, 2);
+            z1 = 2;
+          } else { // (0-0).
+            SETVECTOR3(U, C, A, B);  // PT = ST
+            SETVECTOR3(V, Q, P, R);  // PL = SL
+            SETVECTOR3(pu, 2, 0, 1);
+            SETVECTOR3(pv, 1, 0, 2);
+            z1 = 3; 
+          }
+        }
+      } else { 
+        if (sB > 0) {
+          if (sC < 0) { // (0+-).
+            SETVECTOR3(U, A, B, C);  // I3
+            SETVECTOR3(V, Q, P, R);  // PL = SL
+            SETVECTOR3(pu, 0, 1, 2);
+            SETVECTOR3(pv, 1, 0, 2);
+            z1 = 2;
+          } else {
+            if (sC > 0) { // (0++).
+              SETVECTOR3(U, B, C, A);  // PT = ST x ST
+              SETVECTOR3(V, Q, P, R);  // PL = SL
+              SETVECTOR3(pu, 1, 2, 0);
+              SETVECTOR3(pv, 1, 0, 2);
+              z1 = 1;
+            } else { // (0+0).
+              SETVECTOR3(U, C, A, B);  // PT = ST
+              SETVECTOR3(V, P, Q, R);  // I2
+              SETVECTOR3(pu, 2, 0, 1);
+              SETVECTOR3(pv, 0, 1, 2);
+              z1 = 3; 
+            }
+          }
+        } else { // (00#)
+          if (sC < 0) { // (00-).
+            SETVECTOR3(U, A, B, C);  // I3
+            SETVECTOR3(V, Q, P, R);  // PL = SL
+            SETVECTOR3(pu, 0, 1, 2);
+            SETVECTOR3(pv, 1, 0, 2);
+            z1 = 3; 
+          } else {
+            if (sC > 0) { // (00+).
+              SETVECTOR3(U, A, B, C);  // I3
+              SETVECTOR3(V, P, Q, R);  // I2
+              SETVECTOR3(pu, 0, 1, 2);
+              SETVECTOR3(pv, 0, 1, 2);
+              z1 = 3; 
+            } else { // (000)
+              // Not possible unless ABC is degenerate.
+              // Avoiding compiler warnings.
+              SETVECTOR3(U, A, B, C);  // I3
+              SETVECTOR3(V, P, Q, R);  // I2
+              SETVECTOR3(pu, 0, 1, 2);
+              SETVECTOR3(pv, 0, 1, 2);
+              z1 = 4;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  s1 = orient3d(U[0], U[2], R, V[1]);  // A, C, R, Q
+  s2 = orient3d(U[1], U[2], R, V[0]);  // B, C, R, P
+
+  if (s1 > 0) {
+    return 0;
+  }
+  if (s2 < 0) {
+    return 0;
+  }
+
+  if (level == 0) {
+    return 1;  // They are intersected.
+  }
+
+
+  if (z1 == 1) {
+    if (s1 == 0) {  // (0###)
+      // C = Q.
+      types[0] = (int) SHAREVERT;
+      pos[0] = pu[2]; // C
+      pos[1] = pv[1]; // Q
+      types[1] = (int) DISJOINT;
+    } else {
+      if (s2 == 0) { // (#0##)
+        // C = P.
+        types[0] = (int) SHAREVERT;
+        pos[0] = pu[2]; // C
+        pos[1] = pv[0]; // P
+        types[1] = (int) DISJOINT;
+      } else { // (-+##)
+        // C in [P, Q].
+        types[0] = (int) ACROSSVERT;
+        pos[0] = pu[2]; // C
+        pos[1] = pv[0]; // [P, Q]
+        types[1] = (int) DISJOINT;
+      }
+    }
+    return 4;
+  }
+
+  s3 = orient3d(U[0], U[2], R, V[0]);  // A, C, R, P
+  s4 = orient3d(U[1], U[2], R, V[1]);  // B, C, R, Q
+      
+  if (z1 == 0) {  // (tritri-03)
+    if (s1 < 0) {
+      if (s3 > 0) {
+        if (s4 > 0) {
+          // [P, Q] overlaps [k, l] (-+++).
+          types[0] = (int) ACROSSEDGE;
+          pos[0] = pu[2]; // [C, A]
+          pos[1] = pv[0]; // [P, Q]
+          types[1] = (int) TOUCHFACE;
+          pos[2] = 3;     // [A, B, C]
+          pos[3] = pv[1]; // Q
+        } else {
+          if (s4 == 0) {
+            // Q = l, [P, Q] contains [k, l] (-++0).
+            types[0] = (int) ACROSSEDGE;
+            pos[0] = pu[2]; // [C, A]
+            pos[1] = pv[0]; // [P, Q]
+            types[1] = (int) TOUCHEDGE;
+            pos[2] = pu[1]; // [B, C]
+            pos[3] = pv[1]; // Q
+          } else { // s4 < 0
+            // [P, Q] contains [k, l] (-++-).
+            types[0] = (int) ACROSSEDGE;
+            pos[0] = pu[2]; // [C, A]
+            pos[1] = pv[0]; // [P, Q]
+            types[1] = (int) ACROSSEDGE;
+            pos[2] = pu[1]; // [B, C]
+            pos[3] = pv[0]; // [P, Q]
+          }
+        }
+      } else {
+        if (s3 == 0) {
+          if (s4 > 0) {
+            // P = k, [P, Q] in [k, l] (-+0+).
+            types[0] = (int) TOUCHEDGE;
+            pos[0] = pu[2]; // [C, A]
+            pos[1] = pv[0]; // P
+            types[1] = (int) TOUCHFACE;
+            pos[2] = 3;     // [A, B, C]
+            pos[3] = pv[1]; // Q
+          } else {
+            if (s4 == 0) {
+              // [P, Q] = [k, l] (-+00).
+              types[0] = (int) TOUCHEDGE;
+              pos[0] = pu[2]; // [C, A]
+              pos[1] = pv[0]; // P
+              types[1] = (int) TOUCHEDGE;
+              pos[2] = pu[1]; // [B, C]
+              pos[3] = pv[1]; // Q
+            } else {
+              // P = k, [P, Q] contains [k, l] (-+0-).
+              types[0] = (int) TOUCHEDGE;
+              pos[0] = pu[2]; // [C, A]
+              pos[1] = pv[0]; // P
+              types[1] = (int) ACROSSEDGE;
+              pos[2] = pu[1]; // [B, C]
+              pos[3] = pv[0]; // [P, Q]
+            }
+          }
+        } else { // s3 < 0
+          if (s2 > 0) {
+            if (s4 > 0) {
+              // [P, Q] in [k, l] (-+-+).
+              types[0] = (int) TOUCHFACE;
+              pos[0] = 3;     // [A, B, C]
+              pos[1] = pv[0]; // P
+              types[1] = (int) TOUCHFACE;
+              pos[2] = 3;     // [A, B, C]
+              pos[3] = pv[1]; // Q
+            } else {
+              if (s4 == 0) {
+                // Q = l, [P, Q] in [k, l] (-+-0).
+                types[0] = (int) TOUCHFACE;
+                pos[0] = 3;     // [A, B, C]
+                pos[1] = pv[0]; // P
+                types[1] = (int) TOUCHEDGE;
+                pos[2] = pu[1]; // [B, C]
+                pos[3] = pv[1]; // Q
+              } else { // s4 < 0
+                // [P, Q] overlaps [k, l] (-+--).
+                types[0] = (int) TOUCHFACE;
+                pos[0] = 3;     // [A, B, C]
+                pos[1] = pv[0]; // P
+                types[1] = (int) ACROSSEDGE;
+                pos[2] = pu[1]; // [B, C]
+                pos[3] = pv[0]; // [P, Q]
+              }
+            }
+          } else { // s2 == 0
+            // P = l (#0##).
+            types[0] = (int) TOUCHEDGE;
+            pos[0] = pu[1]; // [B, C]
+            pos[1] = pv[0]; // P
+            types[1] = (int) DISJOINT;
+          }
+        }
+      }
+    } else { // s1 == 0
+      // Q = k (0####)
+      types[0] = (int) TOUCHEDGE;
+      pos[0] = pu[2]; // [C, A]
+      pos[1] = pv[1]; // Q
+      types[1] = (int) DISJOINT;
+    }
+  } else if (z1 == 2) {  // (tritri-23)
+    if (s1 < 0) {
+      if (s3 > 0) {
+        if (s4 > 0) {
+          // [P, Q] overlaps [A, l] (-+++).
+          types[0] = (int) ACROSSVERT;
+          pos[0] = pu[0]; // A
+          pos[1] = pv[0]; // [P, Q]
+          types[1] = (int) TOUCHFACE;
+          pos[2] = 3;     // [A, B, C]
+          pos[3] = pv[1]; // Q
+        } else {
+          if (s4 == 0) {
+            // Q = l, [P, Q] contains [A, l] (-++0).
+            types[0] = (int) ACROSSVERT;
+            pos[0] = pu[0]; // A
+            pos[1] = pv[0]; // [P, Q]
+            types[1] = (int) TOUCHEDGE;
+            pos[2] = pu[1]; // [B, C]
+            pos[3] = pv[1]; // Q
+          } else { // s4 < 0
+            // [P, Q] contains [A, l] (-++-).
+            types[0] = (int) ACROSSVERT;
+            pos[0] = pu[0]; // A
+            pos[1] = pv[0]; // [P, Q]
+            types[1] = (int) ACROSSEDGE;
+            pos[2] = pu[1]; // [B, C]
+            pos[3] = pv[0]; // [P, Q]
+          }
+        }
+      } else {
+        if (s3 == 0) {
+          if (s4 > 0) {
+            // P = A, [P, Q] in [A, l] (-+0+).
+            types[0] = (int) SHAREVERT;
+            pos[0] = pu[0]; // A
+            pos[1] = pv[0]; // P
+            types[1] = (int) TOUCHFACE;
+            pos[2] = 3;     // [A, B, C]
+            pos[3] = pv[1]; // Q
+          } else {
+            if (s4 == 0) {
+              // [P, Q] = [A, l] (-+00).
+              types[0] = (int) SHAREVERT;
+              pos[0] = pu[0]; // A
+              pos[1] = pv[0]; // P
+              types[1] = (int) TOUCHEDGE;
+              pos[2] = pu[1]; // [B, C]
+              pos[3] = pv[1]; // Q
+            } else { // s4 < 0
+              // Q = l, [P, Q] in [A, l] (-+0-).
+              types[0] = (int) SHAREVERT;
+              pos[0] = pu[0]; // A
+              pos[1] = pv[0]; // P
+              types[1] = (int) ACROSSEDGE;
+              pos[2] = pu[1]; // [B, C]
+              pos[3] = pv[0]; // [P, Q]
+            }
+          }
+        } else { // s3 < 0
+          if (s2 > 0) {
+            if (s4 > 0) {
+              // [P, Q] in [A, l] (-+-+).
+              types[0] = (int) TOUCHFACE;
+              pos[0] = 3;     // [A, B, C]
+              pos[1] = pv[0]; // P
+              types[0] = (int) TOUCHFACE;
+              pos[0] = 3;     // [A, B, C]
+              pos[1] = pv[1]; // Q
+            } else {
+              if (s4 == 0) {
+                // Q = l, [P, Q] in [A, l] (-+-0).
+                types[0] = (int) TOUCHFACE;
+                pos[0] = 3;     // [A, B, C]
+                pos[1] = pv[0]; // P
+                types[0] = (int) TOUCHEDGE;
+                pos[0] = pu[1]; // [B, C]
+                pos[1] = pv[1]; // Q
+              } else { // s4 < 0
+                // [P, Q] overlaps [A, l] (-+--).
+                types[0] = (int) TOUCHFACE;
+                pos[0] = 3;     // [A, B, C]
+                pos[1] = pv[0]; // P
+                types[0] = (int) ACROSSEDGE;
+                pos[0] = pu[1]; // [B, C]
+                pos[1] = pv[0]; // [P, Q]
+              }
+            }
+          } else { // s2 == 0
+            // P = l (#0##).
+            types[0] = (int) TOUCHEDGE;
+            pos[0] = pu[1]; // [B, C]
+            pos[1] = pv[0]; // P
+            types[1] = (int) DISJOINT;
+          }
+        }
+      }
+    } else { // s1 == 0
+      // Q = A (0###).
+      types[0] = (int) SHAREVERT;
+      pos[0] = pu[0]; // A
+      pos[1] = pv[1]; // Q
+      types[1] = (int) DISJOINT;
+    }
+  } else if (z1 == 3) {  // (tritri-33)
+    if (s1 < 0) {
+      if (s3 > 0) {
+        if (s4 > 0) {
+          // [P, Q] overlaps [A, B] (-+++).
+          types[0] = (int) ACROSSVERT;
+          pos[0] = pu[0]; // A
+          pos[1] = pv[0]; // [P, Q]
+          types[1] = (int) TOUCHEDGE;
+          pos[2] = pu[0]; // [A, B]
+          pos[3] = pv[1]; // Q
+        } else {
+          if (s4 == 0) {
+            // Q = B, [P, Q] contains [A, B] (-++0).
+            types[0] = (int) ACROSSVERT;
+            pos[0] = pu[0]; // A
+            pos[1] = pv[0]; // [P, Q]
+            types[1] = (int) SHAREVERT;
+            pos[2] = pu[1]; // B
+            pos[3] = pv[1]; // Q
+          } else { // s4 < 0
+            // [P, Q] contains [A, B] (-++-).
+            types[0] = (int) ACROSSVERT;
+            pos[0] = pu[0]; // A
+            pos[1] = pv[0]; // [P, Q]
+            types[1] = (int) ACROSSVERT;
+            pos[2] = pu[1]; // B
+            pos[3] = pv[0]; // [P, Q]
+          }
+        }
+      } else {
+        if (s3 == 0) {
+          if (s4 > 0) {
+            // P = A, [P, Q] in [A, B] (-+0+).
+            types[0] = (int) SHAREVERT;
+            pos[0] = pu[0]; // A
+            pos[1] = pv[0]; // P
+            types[1] = (int) TOUCHEDGE;
+            pos[2] = pu[0]; // [A, B]
+            pos[3] = pv[1]; // Q
+          } else {
+            if (s4 == 0) {
+              // [P, Q] = [A, B] (-+00).
+              types[0] = (int) SHAREEDGE;
+              pos[0] = pu[0]; // [A, B]
+              pos[1] = pv[0]; // [P, Q]
+              types[1] = (int) DISJOINT;
+            } else { // s4 < 0
+              // P= A, [P, Q] in [A, B] (-+0-).
+              types[0] = (int) SHAREVERT;
+              pos[0] = pu[0]; // A
+              pos[1] = pv[0]; // P
+              types[1] = (int) ACROSSVERT;
+              pos[2] = pu[1]; // B
+              pos[3] = pv[0]; // [P, Q]
+            }
+          }
+        } else { // s3 < 0
+          if (s2 > 0) {
+            if (s4 > 0) {
+              // [P, Q] in [A, B] (-+-+).
+              types[0] = (int) TOUCHEDGE;
+              pos[0] = pu[0]; // [A, B]
+              pos[1] = pv[0]; // P
+              types[1] = (int) TOUCHEDGE;
+              pos[2] = pu[0]; // [A, B]
+              pos[3] = pv[1]; // Q
+            } else {
+              if (s4 == 0) {
+                // Q = B, [P, Q] in [A, B] (-+-0).
+                types[0] = (int) TOUCHEDGE;
+                pos[0] = pu[0]; // [A, B]
+                pos[1] = pv[0]; // P
+                types[1] = (int) SHAREVERT;
+                pos[2] = pu[1]; // B
+                pos[3] = pv[1]; // Q
+              } else { // s4 < 0
+                // [P, Q] overlaps [A, B] (-+--).
+                types[0] = (int) TOUCHEDGE;
+                pos[0] = pu[0]; // [A, B]
+                pos[1] = pv[0]; // P
+                types[1] = (int) ACROSSVERT;
+                pos[2] = pu[1]; // B
+                pos[3] = pv[0]; // [P, Q]
+              }
+            }
+          } else { // s2 == 0
+            // P = B (#0##).
+            types[0] = (int) SHAREVERT;
+            pos[0] = pu[1]; // B
+            pos[1] = pv[0]; // P
+            types[1] = (int) DISJOINT;
+          }
+        }
+      }
+    } else { // s1 == 0
+      // Q = A (0###).
+      types[0] = (int) SHAREVERT;
+      pos[0] = pu[0]; // A
+      pos[1] = pv[1]; // Q
+      types[1] = (int) DISJOINT;
+    }
+  }
+
+  return 4;
+}
+
+int tetgenmesh::tri_edge_tail(point A,point B,point C,point P,point Q,point R,
+                              REAL sP,REAL sQ,int level,int *types,int *pos)
+{
+  point U[3], V[3]; //, Ptmp;
+  int pu[3], pv[3]; //, itmp;
+  REAL s1, s2, s3;
+  int z1;
+
+
+  if (sP < 0) {
+    if (sQ < 0) { // (--) disjoint
+      return 0;
+    } else {
+      if (sQ > 0) { // (-+)
+        SETVECTOR3(U, A, B, C);
+        SETVECTOR3(V, P, Q, R);
+        SETVECTOR3(pu, 0, 1, 2);
+        SETVECTOR3(pv, 0, 1, 2);
+        z1 = 0;
+      } else { // (-0)
+        SETVECTOR3(U, A, B, C);
+        SETVECTOR3(V, P, Q, R);
+        SETVECTOR3(pu, 0, 1, 2);
+        SETVECTOR3(pv, 0, 1, 2);
+        z1 = 1;
+      }
+    }
+  } else {
+    if (sP > 0) { // (+-)
+      if (sQ < 0) {
+        SETVECTOR3(U, A, B, C);
+        SETVECTOR3(V, Q, P, R);  // P and Q are flipped.
+        SETVECTOR3(pu, 0, 1, 2);
+        SETVECTOR3(pv, 1, 0, 2);
+        z1 = 0;
+      } else {
+        if (sQ > 0) { // (++) disjoint
+          return 0;
+        } else { // (+0)
+          SETVECTOR3(U, B, A, C); // A and B are flipped.
+          SETVECTOR3(V, P, Q, R);
+          SETVECTOR3(pu, 1, 0, 2);
+          SETVECTOR3(pv, 0, 1, 2);
+          z1 = 1;
+        }
+      }
+    } else { // sP == 0
+      if (sQ < 0) { // (0-)
+        SETVECTOR3(U, A, B, C);
+        SETVECTOR3(V, Q, P, R);  // P and Q are flipped.
+        SETVECTOR3(pu, 0, 1, 2);
+        SETVECTOR3(pv, 1, 0, 2);
+        z1 = 1;
+      } else {
+        if (sQ > 0) { // (0+)
+          SETVECTOR3(U, B, A, C);  // A and B are flipped.
+          SETVECTOR3(V, Q, P, R);  // P and Q are flipped.
+          SETVECTOR3(pu, 1, 0, 2);
+          SETVECTOR3(pv, 1, 0, 2);
+          z1 = 1;
+        } else { // (00)
+          // A, B, C, P, and Q are coplanar.
+          z1 = 2;
+        }
+      }
+    }
+  }
+
+  if (z1 == 2) {
+    // The triangle and the edge are coplanar.
+    return tri_edge_2d(A, B, C, P, Q, R, level, types, pos);
+  }
+
+  s1 = orient3d(U[0], U[1], V[0], V[1]);
+  if (s1 < 0) {
+    return 0;
+  }
+
+  s2 = orient3d(U[1], U[2], V[0], V[1]);
+  if (s2 < 0) {
+    return 0;
+  }
+
+  s3 = orient3d(U[2], U[0], V[0], V[1]);
+  if (s3 < 0) {
+    return 0;
+  }
+
+  if (level == 0) {
+    return 1;  // The are intersected.
+  }
+
+  types[1] = (int) DISJOINT; // No second intersection point.
+
+  if (z1 == 0) {
+    if (s1 > 0) {
+      if (s2 > 0) {
+        if (s3 > 0) { // (+++)
+          // [P, Q] passes interior of [A, B, C].
+          types[0] = (int) ACROSSFACE;
+          pos[0] = 3;  // interior of [A, B, C]
+          pos[1] = 0;  // [P, Q]
+        } else { // s3 == 0 (++0)
+          // [P, Q] intersects [C, A].
+          types[0] = (int) ACROSSEDGE;
+          pos[0] = pu[2];  // [C, A]
+          pos[1] = 0;  // [P, Q]
+        }
+      } else { // s2 == 0
+        if (s3 > 0) { // (+0+)
+          // [P, Q] intersects [B, C].
+          types[0] = (int) ACROSSEDGE;
+          pos[0] = pu[1];  // [B, C]
+          pos[1] = 0;  // [P, Q]
+        } else { // s3 == 0 (+00)
+          // [P, Q] passes C.
+          types[0] = (int) ACROSSVERT;
+          pos[0] = pu[2];  // C
+          pos[1] = 0;  // [P, Q]
+        }
+      }
+    } else { // s1 == 0
+      if (s2 > 0) {
+        if (s3 > 0) { // (0++)
+          // [P, Q] intersects [A, B].
+          types[0] = (int) ACROSSEDGE;
+          pos[0] = pu[0];  // [A, B]
+          pos[1] = 0;  // [P, Q]
+        } else { // s3 == 0 (0+0)
+          // [P, Q] passes A.
+          types[0] = (int) ACROSSVERT;
+          pos[0] = pu[0];  // A
+          pos[1] = 0;  // [P, Q]
+        }
+      } else { // s2 == 0
+        if (s3 > 0) { // (00+)
+          // [P, Q] passes B.
+          types[0] = (int) ACROSSVERT;
+          pos[0] = pu[1];  // B
+          pos[1] = 0;  // [P, Q]
+        }
+      }
+    }
+  } else { // z1 == 1
+    if (s1 > 0) {
+      if (s2 > 0) {
+        if (s3 > 0) { // (+++)
+          // Q lies in [A, B, C].
+          types[0] = (int) TOUCHFACE;
+          pos[0] = 0; // [A, B, C]
+          pos[1] = pv[1]; // Q
+        } else { // s3 == 0 (++0)
+          // Q lies on [C, A].
+          types[0] = (int) TOUCHEDGE;
+          pos[0] = pu[2]; // [C, A]
+          pos[1] = pv[1]; // Q
+        }
+      } else { // s2 == 0
+        if (s3 > 0) { // (+0+)
+          // Q lies on [B, C].
+          types[0] = (int) TOUCHEDGE;
+          pos[0] = pu[1]; // [B, C]
+          pos[1] = pv[1]; // Q
+        } else { // s3 == 0 (+00)
+          // Q = C.
+          types[0] = (int) SHAREVERT;
+          pos[0] = pu[2]; // C
+          pos[1] = pv[1]; // Q
+        }
+      }
+    } else { // s1 == 0
+      if (s2 > 0) {
+        if (s3 > 0) { // (0++)
+          // Q lies on [A, B].
+          types[0] = (int) TOUCHEDGE;
+          pos[0] = pu[0]; // [A, B]
+          pos[1] = pv[1]; // Q
+        } else { // s3 == 0 (0+0)
+          // Q = A.
+          types[0] = (int) SHAREVERT;
+          pos[0] = pu[0]; // A
+          pos[1] = pv[1]; // Q
+        }
+      } else { // s2 == 0
+        if (s3 > 0) { // (00+)
+          // Q = B.
+          types[0] = (int) SHAREVERT;
+          pos[0] = pu[1]; // B
+          pos[1] = pv[1]; // Q
+        }
+      }
+    }
+  }
+
+  // T and E intersect in a single point.
+  return 2;
+}
+
+int tetgenmesh::tri_edge_test(point A, point B, point C, point P, point Q, 
+                              point R, int level, int *types, int *pos)
+{
+  REAL sP, sQ;
+
+  // Test the locations of P and Q with respect to ABC.
+  sP = orient3d(A, B, C, P);
+  sQ = orient3d(A, B, C, Q);
+
+  return tri_edge_tail(A, B, C, P, Q, R, sP, sQ, level, types, pos);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// tri_tri_inter()    Test whether two triangle (abc) and (opq) are          //
+//                    intersecting or not.                                   //
+//                                                                           //
+// Return 0 if they are disjoint. Otherwise, return 1. 'type' returns one of //
+// the four cases: SHAREVERTEX, SHAREEDGE, SHAREFACE, and INTERSECT.         //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::tri_edge_inter_tail(REAL* A, REAL* B, REAL* C,  REAL* P, 
+                                    REAL* Q, REAL s_p, REAL s_q)
+{
+  int types[2], pos[4];
+  int ni;  // =0, 2, 4
+
+  ni = tri_edge_tail(A, B, C, P, Q, NULL, s_p, s_q, 1, types, pos);
+
+  if (ni > 0) {
+    if (ni == 2) {
+      // Get the intersection type.
+      if (types[0] == (int) SHAREVERT) {
+        return (int) SHAREVERT;
+      } else {
+        return (int) INTERSECT;
+      }
+    } else if (ni == 4) { 
+      // There may be two intersections.
+      if (types[0] == (int) SHAREVERT) {
+        if (types[1] == (int) DISJOINT) {
+          return (int) SHAREVERT;
+        } else {
+          return (int) INTERSECT;
+        }
+      } else {
+        if (types[0] == (int) SHAREEDGE) {
+          return (int) SHAREEDGE;
+        } else {
+          return (int) INTERSECT;
+        }
+      }
+    }
+  }
+
+  return (int) DISJOINT;
+}
+
+int tetgenmesh::tri_tri_inter(REAL* A,REAL* B,REAL* C,REAL* O,REAL* P,REAL* Q)
+{
+  REAL s_o, s_p, s_q;
+  REAL s_a, s_b, s_c;
+
+  s_o = orient3d(A, B, C, O);
+  s_p = orient3d(A, B, C, P);
+  s_q = orient3d(A, B, C, Q);
+  if ((s_o * s_p > 0.0) && (s_o * s_q > 0.0)) {
+    // o, p, q are all in the same halfspace of ABC.
+    return 0; // DISJOINT;
+  }
+
+  s_a = orient3d(O, P, Q, A);
+  s_b = orient3d(O, P, Q, B);
+  s_c = orient3d(O, P, Q, C);
+  if ((s_a * s_b > 0.0) && (s_a * s_c > 0.0)) {
+    // a, b, c are all in the same halfspace of OPQ.
+    return 0; // DISJOINT;
+  }
+
+  int abcop, abcpq, abcqo;
+  int shareedge = 0;
+
+  abcop = tri_edge_inter_tail(A, B, C, O, P, s_o, s_p);
+  if (abcop == (int) INTERSECT) {
+    return (int) INTERSECT;
+  } else if (abcop == (int) SHAREEDGE) {
+    shareedge++;
+  }
+  abcpq = tri_edge_inter_tail(A, B, C, P, Q, s_p, s_q);
+  if (abcpq == (int) INTERSECT) {
+    return (int) INTERSECT;
+  } else if (abcpq == (int) SHAREEDGE) {
+    shareedge++;
+  }
+  abcqo = tri_edge_inter_tail(A, B, C, Q, O, s_q, s_o);
+  if (abcqo == (int) INTERSECT) {
+    return (int) INTERSECT;
+  } else if (abcqo == (int) SHAREEDGE) {
+    shareedge++;
+  }
+  if (shareedge == 3) {
+    // opq are coincident with abc.
+    return (int) SHAREFACE;
+  }
+
+  // Continue to detect whether opq and abc are intersecting or not.
+  int opqab, opqbc, opqca;
+
+  opqab = tri_edge_inter_tail(O, P, Q, A, B, s_a, s_b);
+  if (opqab == (int) INTERSECT) {
+    return (int) INTERSECT;
+  }
+  opqbc = tri_edge_inter_tail(O, P, Q, B, C, s_b, s_c);
+  if (opqbc == (int) INTERSECT) {
+    return (int) INTERSECT;
+  }
+  opqca = tri_edge_inter_tail(O, P, Q, C, A, s_c, s_a);
+  if (opqca == (int) INTERSECT) {
+    return (int) INTERSECT;
+  }
+
+  // At this point, two triangles are not intersecting and not coincident.
+  //   They may be share an edge, or share a vertex, or disjoint.
+  if (abcop == (int) SHAREEDGE) {
+    // op is coincident with an edge of abc.
+    return (int) SHAREEDGE;
+  }
+  if (abcpq == (int) SHAREEDGE) {
+    // pq is coincident with an edge of abc.
+    return (int) SHAREEDGE;
+  }
+  if (abcqo == (int) SHAREEDGE) {
+    // qo is coincident with an edge of abc.
+    return (int) SHAREEDGE;
+  }
+
+  // They may share a vertex or disjoint.
+  if (abcop == (int) SHAREVERT) {
+    return (int) SHAREVERT;
+  }
+  if (abcpq == (int) SHAREVERT) {
+    // q is the coincident vertex.
+    return (int) SHAREVERT;
+  }
+
+  // They are disjoint.
+  return (int) DISJOINT;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// lu_decmp()    Compute the LU decomposition of a matrix.                   //
+//                                                                           //
+// Compute the LU decomposition of a (non-singular) square matrix A using    //
+// partial pivoting and implicit row exchanges.  The result is:              //
+//     A = P * L * U,                                                        //
+// where P is a permutation matrix, L is unit lower triangular, and U is     //
+// upper triangular.  The factored form of A is used in combination with     //
+// 'lu_solve()' to solve linear equations: Ax = b, or invert a matrix.       //
+//                                                                           //
+// The inputs are a square matrix 'lu[N..n+N-1][N..n+N-1]', it's size is 'n'.//
+// On output, 'lu' is replaced by the LU decomposition of a rowwise permuta- //
+// tion of itself, 'ps[N..n+N-1]' is an output vector that records the row   //
+// permutation effected by the partial pivoting, effectively,  'ps' array    //
+// tells the user what the permutation matrix P is; 'd' is output as +1/-1   //
+// depending on whether the number of row interchanges was even or odd,      //
+// respectively.                                                             //
+//                                                                           //
+// Return true if the LU decomposition is successfully computed, otherwise,  //
+// return false in case that A is a singular matrix.                         //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+bool tetgenmesh::lu_decmp(REAL lu[4][4], int n, int* ps, REAL* d, int N)
+{
+  REAL scales[4];
+  REAL pivot, biggest, mult, tempf;
+  int pivotindex = 0;
+  int i, j, k;
+
+  *d = 1.0;                                      // No row interchanges yet.
+
+  for (i = N; i < n + N; i++) {                             // For each row.
+    // Find the largest element in each row for row equilibration
+    biggest = 0.0;
+    for (j = N; j < n + N; j++)
+      if (biggest < (tempf = fabs(lu[i][j])))
+        biggest  = tempf;
+    if (biggest != 0.0)
+      scales[i] = 1.0 / biggest;
+    else {
+      scales[i] = 0.0;
+      return false;                            // Zero row: singular matrix.
+    }
+    ps[i] = i;                                 // Initialize pivot sequence.
+  }
+
+  for (k = N; k < n + N - 1; k++) {                      // For each column.
+    // Find the largest element in each column to pivot around.
+    biggest = 0.0;
+    for (i = k; i < n + N; i++) {
+      if (biggest < (tempf = fabs(lu[ps[i]][k]) * scales[ps[i]])) {
+        biggest = tempf;
+        pivotindex = i;
+      }
+    }
+    if (biggest == 0.0) {
+      return false;                         // Zero column: singular matrix.
+    }
+    if (pivotindex != k) {                         // Update pivot sequence.
+      j = ps[k];
+      ps[k] = ps[pivotindex];
+      ps[pivotindex] = j;
+      *d = -(*d);                          // ...and change the parity of d.
+    }
+
+    // Pivot, eliminating an extra variable  each time
+    pivot = lu[ps[k]][k];
+    for (i = k + 1; i < n + N; i++) {
+      lu[ps[i]][k] = mult = lu[ps[i]][k] / pivot;
+      if (mult != 0.0) {
+        for (j = k + 1; j < n + N; j++)
+          lu[ps[i]][j] -= mult * lu[ps[k]][j];
+      }
+    }
+  }
+
+  // (lu[ps[n + N - 1]][n + N - 1] == 0.0) ==> A is singular.
+  return lu[ps[n + N - 1]][n + N - 1] != 0.0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// lu_solve()    Solves the linear equation:  Ax = b,  after the matrix A    //
+//               has been decomposed into the lower and upper triangular     //
+//               matrices L and U, where A = LU.                             //
+//                                                                           //
+// 'lu[N..n+N-1][N..n+N-1]' is input, not as the matrix 'A' but rather as    //
+// its LU decomposition, computed by the routine 'lu_decmp'; 'ps[N..n+N-1]'  //
+// is input as the permutation vector returned by 'lu_decmp';  'b[N..n+N-1]' //
+// is input as the right-hand side vector, and returns with the solution     //
+// vector. 'lu', 'n', and 'ps' are not modified by this routine and can be   //
+// left in place for successive calls with different right-hand sides 'b'.   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::lu_solve(REAL lu[4][4], int n, int* ps, REAL* b, int N)
+{
+  int i, j;
+  REAL X[4], dot;
+
+  for (i = N; i < n + N; i++) X[i] = 0.0;
+
+  // Vector reduction using U triangular matrix.
+  for (i = N; i < n + N; i++) {
+    dot = 0.0;
+    for (j = N; j < i + N; j++)
+      dot += lu[ps[i]][j] * X[j];
+    X[i] = b[ps[i]] - dot;
+  }
+
+  // Back substitution, in L triangular matrix.
+  for (i = n + N - 1; i >= N; i--) {
+    dot = 0.0;
+    for (j = i + 1; j < n + N; j++)
+      dot += lu[ps[i]][j] * X[j];
+    X[i] = (X[i] - dot) / lu[ps[i]][i];
+  }
+
+  for (i = N; i < n + N; i++) b[i] = X[i];
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// incircle3d()    3D in-circle test.                                        //
+//                                                                           //
+// Return a negative value if pd is inside the circumcircle of the triangle  //
+// pa, pb, and pc.                                                           //
+//                                                                           //
+// IMPORTANT: It assumes that [a,b] is the common edge, i.e., the two input  //
+// triangles are [a,b,c] and [b,a,d].                                        //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+REAL tetgenmesh::incircle3d(point pa, point pb, point pc, point pd)
+{
+  REAL area2[2], n1[3], n2[3], c[3];
+  REAL sign, r, d;
+
+  // Calculate the areas of the two triangles [a, b, c] and [b, a, d].
+  facenormal(pa, pb, pc, n1, 1, NULL);
+  area2[0] = dot(n1, n1);
+  facenormal(pb, pa, pd, n2, 1, NULL);
+  area2[1] = dot(n2, n2);
+
+  if (area2[0] > area2[1]) {
+    // Choose [a, b, c] as the base triangle.
+    circumsphere(pa, pb, pc, NULL, c, &r);
+    d = distance(c, pd);
+  } else {
+    // Choose [b, a, d] as the base triangle.
+    if (area2[1] > 0) {
+      circumsphere(pb, pa, pd, NULL, c, &r);
+      d = distance(c, pc);
+    } else {
+      // The four points are collinear. This case only happens on the boundary.
+      return 0; // Return "not inside".
+    }
+  }
+
+  sign = d - r;
+  if (fabs(sign) / r < b->epsilon) {
+    sign = 0;
+  }
+
+  return sign;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// facenormal()    Calculate the normal of the face.                         //
+//                                                                           //
+// The normal of the face abc can be calculated by the cross product of 2 of //
+// its 3 edge vectors.  A better choice of two edge vectors will reduce the  //
+// numerical error during the calculation.  Burdakov proved that the optimal //
+// basis problem is equivalent to the minimum spanning tree problem with the //
+// edge length be the functional, see Burdakov, "A greedy algorithm for the  //
+// optimal basis problem", BIT 37:3 (1997), 591-599. If 'pivot' > 0, the two //
+// short edges in abc are chosen for the calculation.                        //
+//                                                                           //
+// If 'lav' is not NULL and if 'pivot' is set, the average edge length of    //
+// the edges of the face [a,b,c] is returned.                                //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::facenormal(point pa, point pb, point pc, REAL *n, int pivot,
+                            REAL* lav)
+{
+  REAL v1[3], v2[3], v3[3], *pv1, *pv2;
+  REAL L1, L2, L3;
+
+  v1[0] = pb[0] - pa[0];  // edge vector v1: a->b
+  v1[1] = pb[1] - pa[1];
+  v1[2] = pb[2] - pa[2];
+  v2[0] = pa[0] - pc[0];  // edge vector v2: c->a
+  v2[1] = pa[1] - pc[1];
+  v2[2] = pa[2] - pc[2];
+
+  // Default, normal is calculated by: v1 x (-v2) (see Fig. fnormal).
+  if (pivot > 0) {
+    // Choose edge vectors by Burdakov's algorithm.
+    v3[0] = pc[0] - pb[0];  // edge vector v3: b->c
+    v3[1] = pc[1] - pb[1];
+    v3[2] = pc[2] - pb[2];
+    L1 = dot(v1, v1);
+    L2 = dot(v2, v2);
+    L3 = dot(v3, v3);
+    // Sort the three edge lengths.
+    if (L1 < L2) {
+      if (L2 < L3) {
+        pv1 = v1; pv2 = v2; // n = v1 x (-v2).
+      } else {
+        pv1 = v3; pv2 = v1; // n = v3 x (-v1).
+      }
+    } else {
+      if (L1 < L3) {
+        pv1 = v1; pv2 = v2; // n = v1 x (-v2).
+      } else {
+        pv1 = v2; pv2 = v3; // n = v2 x (-v3).
+      }
+    }
+    if (lav) {
+      // return the average edge length.
+      *lav = (sqrt(L1) + sqrt(L2) + sqrt(L3)) / 3.0;
+    }
+  } else {
+    pv1 = v1; pv2 = v2; // n = v1 x (-v2).
+  }
+
+  // Calculate the face normal.
+  cross(pv1, pv2, n);
+  // Inverse the direction;
+  n[0] = -n[0];
+  n[1] = -n[1];
+  n[2] = -n[2];
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// shortdistance()    Returns the shortest distance from point p to a line   //
+//                    defined by two points e1 and e2.                       //
+//                                                                           //
+// First compute the projection length l_p of the vector v1 = p - e1 along   //
+// the vector v2 = e2 - e1. Then Pythagoras' Theorem is used to compute the  //
+// shortest distance.                                                        //
+//                                                                           //
+// This routine allows that p is collinear with the line. In this case, the  //
+// return value is zero. The two points e1 and e2 should not be identical.   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+REAL tetgenmesh::shortdistance(REAL* p, REAL* e1, REAL* e2)
+{
+  REAL v1[3], v2[3];
+  REAL len, l_p;
+
+  v1[0] = e2[0] - e1[0];
+  v1[1] = e2[1] - e1[1];
+  v1[2] = e2[2] - e1[2];
+  v2[0] = p[0] - e1[0];
+  v2[1] = p[1] - e1[1];
+  v2[2] = p[2] - e1[2];
+
+  len = sqrt(dot(v1, v1));
+
+  v1[0] /= len;
+  v1[1] /= len;
+  v1[2] /= len;
+  l_p = dot(v1, v2);
+
+  return sqrt(dot(v2, v2) - l_p * l_p);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// triarea()    Return the area of a triangle.                               //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+REAL tetgenmesh::triarea(REAL* pa, REAL* pb, REAL* pc)
+{
+  REAL A[4][4];  
+
+  // Compute the coefficient matrix A (3x3).
+  A[0][0] = pb[0] - pa[0];
+  A[0][1] = pb[1] - pa[1];
+  A[0][2] = pb[2] - pa[2]; // vector V1 (pa->pb)
+  A[1][0] = pc[0] - pa[0];
+  A[1][1] = pc[1] - pa[1];
+  A[1][2] = pc[2] - pa[2]; // vector V2 (pa->pc)
+
+  cross(A[0], A[1], A[2]); // vector V3 (V1 X V2)
+
+  return 0.5 * sqrt(dot(A[2], A[2])); // The area of [a,b,c].
+}
+
+REAL tetgenmesh::orient3dfast(REAL *pa, REAL *pb, REAL *pc, REAL *pd)
+{
+  REAL adx, bdx, cdx;
+  REAL ady, bdy, cdy;
+  REAL adz, bdz, cdz;
+
+  adx = pa[0] - pd[0];
+  bdx = pb[0] - pd[0];
+  cdx = pc[0] - pd[0];
+  ady = pa[1] - pd[1];
+  bdy = pb[1] - pd[1];
+  cdy = pc[1] - pd[1];
+  adz = pa[2] - pd[2];
+  bdz = pb[2] - pd[2];
+  cdz = pc[2] - pd[2];
+
+  return adx * (bdy * cdz - bdz * cdy)
+       + bdx * (cdy * adz - cdz * ady)
+       + cdx * (ady * bdz - adz * bdy);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// interiorangle()    Return the interior angle (0 - 2 * PI) between vectors //
+//                    o->p1 and o->p2.                                       //
+//                                                                           //
+// 'n' is the normal of the plane containing face (o, p1, p2).  The interior //
+// angle is the total angle rotating from o->p1 around n to o->p2.  Exchange //
+// the position of p1 and p2 will get the complement angle of the other one. //
+// i.e., interiorangle(o, p1, p2) = 2 * PI - interiorangle(o, p2, p1).  Set  //
+// 'n' be NULL if you only want the interior angle between 0 - PI.           //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+REAL tetgenmesh::interiorangle(REAL* o, REAL* p1, REAL* p2, REAL* n)
+{
+  REAL v1[3], v2[3], np[3];
+  REAL theta, costheta, lenlen;
+  REAL ori, len1, len2;
+
+  // Get the interior angle (0 - PI) between o->p1, and o->p2.
+  v1[0] = p1[0] - o[0];
+  v1[1] = p1[1] - o[1];
+  v1[2] = p1[2] - o[2];
+  v2[0] = p2[0] - o[0];
+  v2[1] = p2[1] - o[1];
+  v2[2] = p2[2] - o[2];
+  len1 = sqrt(dot(v1, v1));
+  len2 = sqrt(dot(v2, v2));
+  lenlen = len1 * len2;
+
+  costheta = dot(v1, v2) / lenlen;
+  if (costheta > 1.0) {
+    costheta = 1.0; // Roundoff. 
+  } else if (costheta < -1.0) {
+    costheta = -1.0; // Roundoff. 
+  }
+  theta = acos(costheta);
+  if (n != NULL) {
+    // Get a point above the face (o, p1, p2);
+    np[0] = o[0] + n[0];
+    np[1] = o[1] + n[1];
+    np[2] = o[2] + n[2];
+    // Adjust theta (0 - 2 * PI).
+    ori = orient3d(p1, o, np, p2);
+    if (ori > 0.0) {
+      theta = 2 * PI - theta;
+    }
+  }
+
+  return theta;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// projpt2edge()    Return the projection point from a point to an edge.     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::projpt2edge(REAL* p, REAL* e1, REAL* e2, REAL* prj)
+{
+  REAL v1[3], v2[3];
+  REAL len, l_p;
+
+  v1[0] = e2[0] - e1[0];
+  v1[1] = e2[1] - e1[1];
+  v1[2] = e2[2] - e1[2];
+  v2[0] = p[0] - e1[0];
+  v2[1] = p[1] - e1[1];
+  v2[2] = p[2] - e1[2];
+
+  len = sqrt(dot(v1, v1));
+  v1[0] /= len;
+  v1[1] /= len;
+  v1[2] /= len;
+  l_p = dot(v1, v2);
+
+  prj[0] = e1[0] + l_p * v1[0];
+  prj[1] = e1[1] + l_p * v1[1];
+  prj[2] = e1[2] + l_p * v1[2];
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// projpt2face()    Return the projection point from a point to a face.      //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::projpt2face(REAL* p, REAL* f1, REAL* f2, REAL* f3, REAL* prj)
+{
+  REAL fnormal[3], v1[3];
+  REAL len, dist;
+
+  // Get the unit face normal.
+  facenormal(f1, f2, f3, fnormal, 1, NULL);
+  len = sqrt(fnormal[0]*fnormal[0] + fnormal[1]*fnormal[1] + 
+             fnormal[2]*fnormal[2]);
+  fnormal[0] /= len;
+  fnormal[1] /= len;
+  fnormal[2] /= len;
+  // Get the vector v1 = |p - f1|.
+  v1[0] = p[0] - f1[0];
+  v1[1] = p[1] - f1[1];
+  v1[2] = p[2] - f1[2];
+  // Get the project distance.
+  dist = dot(fnormal, v1);
+  
+  // Get the project point.
+  prj[0] = p[0] - dist * fnormal[0];
+  prj[1] = p[1] - dist * fnormal[1];
+  prj[2] = p[2] - dist * fnormal[2];
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// tetalldihedral()    Get all (six) dihedral angles of a tet.               //
+//                                                                           //
+// If 'cosdd' is not NULL, it returns the cosines of the 6 dihedral angles,  //
+// the edge indices are given in the global array 'edge2ver'. If 'cosmaxd'   //
+// (or 'cosmind') is not NULL, it returns the cosine of the maximal (or      //
+// minimal) dihedral angle.                                                  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+bool tetgenmesh::tetalldihedral(point pa, point pb, point pc, point pd,
+                                REAL* cosdd, REAL* cosmaxd, REAL* cosmind)
+{
+  REAL N[4][3], vol, cosd, len;
+  int f1 = 0, f2 = 0, i, j;
+
+  vol = 0; // Check if the tet is valid or not.
+
+  // Get four normals of faces of the tet.
+  tetallnormal(pa, pb, pc, pd, N, &vol);
+
+  if (vol > 0) {
+    // Normalize the normals.
+    for (i = 0; i < 4; i++) {
+      len = sqrt(dot(N[i], N[i]));
+      if (len != 0.0) {
+        for (j = 0; j < 3; j++) N[i][j] /= len;
+      } else {
+        // There are degeneracies, such as duplicated vertices.
+        vol = 0; //assert(0);
+      }
+    }
+  }
+
+  if (vol <= 0) { // if (vol == 0.0) {
+    // A degenerated tet or an inverted tet.
+    facenormal(pc, pb, pd, N[0], 1, NULL);
+    facenormal(pa, pc, pd, N[1], 1, NULL);
+    facenormal(pb, pa, pd, N[2], 1, NULL);
+    facenormal(pa, pb, pc, N[3], 1, NULL);
+    // Normalize the normals.
+    for (i = 0; i < 4; i++) {
+      len = sqrt(dot(N[i], N[i]));
+      if (len != 0.0) {
+        for (j = 0; j < 3; j++) N[i][j] /= len;
+      } else {
+        // There are degeneracies, such as duplicated vertices.
+        break; // Not a valid normal.
+      }
+    }
+    if (i < 4) {
+      // Do not calculate dihedral angles.
+      // Set all angles be 0 degree. There will be no quality optimization for
+      //   this tet! Use volume optimization to correct it.
+      if (cosdd != NULL) {
+        for (i = 0; i < 6; i++) {
+          cosdd[i] = -1.0; // 180 degree.
+        }
+      }
+      // This tet has zero volume.
+      if (cosmaxd != NULL) {
+        *cosmaxd = -1.0; // 180 degree.
+      }
+      if (cosmind != NULL) {
+        *cosmind = -1.0; // 180 degree.
+      }
+      return false;
+    }
+  }
+
+  // Calculate the cosine of the dihedral angles of the edges.
+  for (i = 0; i < 6; i++) {
+    switch (i) {
+    case 0: f1 = 0; f2 = 1; break; // [c,d].
+    case 1: f1 = 1; f2 = 2; break; // [a,d].
+    case 2: f1 = 2; f2 = 3; break; // [a,b].
+    case 3: f1 = 0; f2 = 3; break; // [b,c].
+    case 4: f1 = 2; f2 = 0; break; // [b,d].
+    case 5: f1 = 1; f2 = 3; break; // [a,c].
+    }
+    cosd = -dot(N[f1], N[f2]);
+    if (cosd < -1.0) cosd = -1.0; // Rounding.
+    if (cosd >  1.0) cosd =  1.0; // Rounding.
+    if (cosdd) cosdd[i] = cosd;
+    if (cosmaxd || cosmind) {
+      if (i == 0) {
+        if (cosmaxd) *cosmaxd = cosd;
+        if (cosmind) *cosmind = cosd;
+      } else {
+        if (cosmaxd) *cosmaxd = cosd < *cosmaxd ? cosd : *cosmaxd;
+        if (cosmind) *cosmind = cosd > *cosmind ? cosd : *cosmind;
+      }
+    }
+  }
+
+  return true;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// tetallnormal()    Get the in-normals of the four faces of a given tet.    //
+//                                                                           //
+// Let tet be abcd. N[4][3] returns the four normals, which are: N[0] cbd,   //
+// N[1] acd, N[2] bad, N[3] abc (exactly corresponding to the face indices   //
+// of the mesh data structure). These normals are unnormalized.              //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::tetallnormal(point pa, point pb, point pc, point pd,
+                              REAL N[4][3], REAL* volume)
+{
+  REAL A[4][4], rhs[4], D;
+  int indx[4];
+  int i, j;
+
+  // get the entries of A[3][3].
+  for (i = 0; i < 3; i++) A[0][i] = pa[i] - pd[i];  // d->a vec
+  for (i = 0; i < 3; i++) A[1][i] = pb[i] - pd[i];  // d->b vec
+  for (i = 0; i < 3; i++) A[2][i] = pc[i] - pd[i];  // d->c vec
+
+  // Compute the inverse of matrix A, to get 3 normals of the 4 faces.
+  if (lu_decmp(A, 3, indx, &D, 0)) { // Decompose the matrix just once.
+    if (volume != NULL) {
+      // Get the volume of the tet.
+      *volume = fabs((A[indx[0]][0] * A[indx[1]][1] * A[indx[2]][2])) / 6.0;
+    }
+    for (j = 0; j < 3; j++) {
+      for (i = 0; i < 3; i++) rhs[i] = 0.0;
+      rhs[j] = 1.0;  // Positive means the inside direction
+      lu_solve(A, 3, indx, rhs, 0);
+      for (i = 0; i < 3; i++) N[j][i] = rhs[i];
+    }
+    // Get the fourth normal by summing up the first three.
+    for (i = 0; i < 3; i++) N[3][i] = - N[0][i] - N[1][i] - N[2][i];
+  } else {
+    // The tet is degenerated.
+    if (volume != NULL) {
+      *volume = 0;
+    }
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// tetaspectratio()    Calculate the aspect ratio of the tetrahedron.        //
+//                                                                           //
+// The aspect ratio of a tet is L/h, where L is the longest edge length, and //
+// h is the shortest height of the tet.                                      //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+REAL tetgenmesh::tetaspectratio(point pa, point pb, point pc, point pd)
+{
+  REAL V[6][3], edgelength[6], longlen;
+  REAL vda[3], vdb[3], vdc[3];
+  REAL N[4][3], A[4][4], rhs[4], D;
+  REAL H[4], volume, minheightinv;
+  int indx[4];
+  int i, j; 
+
+  // Set the edge vectors: V[0], ..., V[5]
+  for (i = 0; i < 3; i++) V[0][i] = pa[i] - pd[i]; 
+  for (i = 0; i < 3; i++) V[1][i] = pb[i] - pd[i]; 
+  for (i = 0; i < 3; i++) V[2][i] = pc[i] - pd[i]; 
+  for (i = 0; i < 3; i++) V[3][i] = pb[i] - pa[i]; 
+  for (i = 0; i < 3; i++) V[4][i] = pc[i] - pb[i]; 
+  for (i = 0; i < 3; i++) V[5][i] = pa[i] - pc[i]; 
+
+  // Get the squares of the edge lengths.
+  for (i = 0; i < 6; i++) edgelength[i] = dot(V[i], V[i]);
+
+  // Calculate the longest and shortest edge length.
+  longlen = edgelength[0];
+  for (i = 1; i < 6; i++) {
+    longlen  = edgelength[i] > longlen ? edgelength[i] : longlen;
+  }
+
+  // Set the matrix A = [vda, vdb, vdc]^T.
+  for (i = 0; i < 3; i++) A[0][i] = vda[i] = pa[i] - pd[i];
+  for (i = 0; i < 3; i++) A[1][i] = vdb[i] = pb[i] - pd[i];
+  for (i = 0; i < 3; i++) A[2][i] = vdc[i] = pc[i] - pd[i];
+  // Lu-decompose the matrix A.
+  lu_decmp(A, 3, indx, &D, 0);
+  // Get the volume of abcd.
+  volume = (A[indx[0]][0] * A[indx[1]][1] * A[indx[2]][2]) / 6.0;
+  // Check if it is zero.
+  if (volume == 0.0) return 1.0e+200; // A degenerate tet.
+
+  // Compute the 4 face normals (N[0], ..., N[3]).
+  for (j = 0; j < 3; j++) {
+    for (i = 0; i < 3; i++) rhs[i] = 0.0;
+    rhs[j] = 1.0;  // Positive means the inside direction
+    lu_solve(A, 3, indx, rhs, 0);
+    for (i = 0; i < 3; i++) N[j][i] = rhs[i];
+  }
+  // Get the fourth normal by summing up the first three.
+  for (i = 0; i < 3; i++) N[3][i] = - N[0][i] - N[1][i] - N[2][i];
+  // Normalized the normals.
+  for (i = 0; i < 4; i++) {
+    // H[i] is the inverse of the height of its corresponding face.
+    H[i] = sqrt(dot(N[i], N[i]));
+    // if (H[i] > 0.0) {
+    //   for (j = 0; j < 3; j++) N[i][j] /= H[i];
+    // }
+  }
+  // Get the radius of the inscribed sphere.
+  // insradius = 1.0 / (H[0] + H[1] + H[2] + H[3]);
+  // Get the biggest H[i] (corresponding to the smallest height).
+  minheightinv = H[0];
+  for (i = 1; i < 4; i++) {
+    if (H[i] > minheightinv) minheightinv = H[i];
+  }
+
+  return sqrt(longlen) * minheightinv;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// circumsphere()    Calculate the smallest circumsphere (center and radius) //
+//                   of the given three or four points.                      //
+//                                                                           //
+// The circumsphere of four points (a tetrahedron) is unique if they are not //
+// degenerate. If 'pd = NULL', the smallest circumsphere of three points is  //
+// the diametral sphere of the triangle if they are not degenerate.          //
+//                                                                           //
+// Return TRUE if the input points are not degenerate and the circumcenter   //
+// and circumradius are returned in 'cent' and 'radius' respectively if they //
+// are not NULLs.  Otherwise, return FALSE, the four points are co-planar.   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+bool tetgenmesh::circumsphere(REAL* pa, REAL* pb, REAL* pc, REAL* pd, 
+                              REAL* cent, REAL* radius)
+{
+  REAL A[4][4], rhs[4], D;
+  int indx[4];
+
+  // Compute the coefficient matrix A (3x3).
+  A[0][0] = pb[0] - pa[0];
+  A[0][1] = pb[1] - pa[1];
+  A[0][2] = pb[2] - pa[2];
+  A[1][0] = pc[0] - pa[0];
+  A[1][1] = pc[1] - pa[1];
+  A[1][2] = pc[2] - pa[2];
+  if (pd != NULL) {
+    A[2][0] = pd[0] - pa[0];
+    A[2][1] = pd[1] - pa[1]; 
+    A[2][2] = pd[2] - pa[2];
+  } else {
+    cross(A[0], A[1], A[2]);
+  }
+
+  // Compute the right hand side vector b (3x1).
+  rhs[0] = 0.5 * dot(A[0], A[0]);
+  rhs[1] = 0.5 * dot(A[1], A[1]);
+  if (pd != NULL) {
+    rhs[2] = 0.5 * dot(A[2], A[2]);
+  } else {
+    rhs[2] = 0.0;
+  }
+
+  // Solve the 3 by 3 equations use LU decomposition with partial pivoting
+  //   and backward and forward substitute..
+  if (!lu_decmp(A, 3, indx, &D, 0)) {
+    if (radius != (REAL *) NULL) *radius = 0.0;
+    return false;
+  }    
+  lu_solve(A, 3, indx, rhs, 0);
+  if (cent != (REAL *) NULL) {
+    cent[0] = pa[0] + rhs[0];
+    cent[1] = pa[1] + rhs[1];
+    cent[2] = pa[2] + rhs[2];
+  }
+  if (radius != (REAL *) NULL) {
+    *radius = sqrt(rhs[0] * rhs[0] + rhs[1] * rhs[1] + rhs[2] * rhs[2]);
+  }
+  return true;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// orthosphere()    Calulcate the orthosphere of four weighted points.       //
+//                                                                           //
+// A weighted point (p, P^2) can be interpreted as a sphere centered at the  //
+// point 'p' with a radius 'P'. The 'height' of 'p' is pheight = p[0]^2 +    //
+// p[1]^2 + p[2]^2 - P^2.                                                    //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+bool tetgenmesh::orthosphere(REAL* pa, REAL* pb, REAL* pc, REAL* pd,
+                             REAL  aheight, REAL bheight, REAL cheight, 
+                             REAL  dheight, REAL* orthocent, REAL* radius)
+{
+  REAL A[4][4], rhs[4], D;
+  int indx[4];
+
+  // Set the coefficient matrix A (4 x 4).
+  A[0][0] = 1.0; A[0][1] = pa[0]; A[0][2] = pa[1]; A[0][3] = pa[2];
+  A[1][0] = 1.0; A[1][1] = pb[0]; A[1][2] = pb[1]; A[1][3] = pb[2];
+  A[2][0] = 1.0; A[2][1] = pc[0]; A[2][2] = pc[1]; A[2][3] = pc[2];
+  A[3][0] = 1.0; A[3][1] = pd[0]; A[3][2] = pd[1]; A[3][3] = pd[2];
+
+  // Set the right hand side vector (4 x 1).
+  rhs[0] = 0.5 * aheight;
+  rhs[1] = 0.5 * bheight;
+  rhs[2] = 0.5 * cheight;
+  rhs[3] = 0.5 * dheight;
+
+  // Solve the 4 by 4 equations use LU decomposition with partial pivoting
+  //   and backward and forward substitute..
+  if (!lu_decmp(A, 4, indx, &D, 0)) {
+    if (radius != (REAL *) NULL) *radius = 0.0;
+    return false;
+  }
+  lu_solve(A, 4, indx, rhs, 0);
+
+  if (orthocent != (REAL *) NULL) {
+    orthocent[0] = rhs[1];
+    orthocent[1] = rhs[2];
+    orthocent[2] = rhs[3];
+  }
+  if (radius != (REAL *) NULL) {
+    // rhs[0] = - rheight / 2;
+    // rheight  = - 2 * rhs[0];
+    //          =  r[0]^2 + r[1]^2 + r[2]^2 - radius^2
+    // radius^2 = r[0]^2 + r[1]^2 + r[2]^2 -rheight
+    //          = r[0]^2 + r[1]^2 + r[2]^2 + 2 * rhs[0]
+    *radius = sqrt(rhs[1] * rhs[1] + rhs[2] * rhs[2] + rhs[3] * rhs[3]
+                   + 2.0 * rhs[0]);
+  }
+  return true;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// planelineint()    Calculate the intersection of a line and a plane.       //
+//                                                                           //
+// The equation of a plane (points P are on the plane with normal N and P3   //
+// on the plane) can be written as: N dot (P - P3) = 0. The equation of the  //
+// line (points P on the line passing through P1 and P2) can be written as:  //
+// P = P1 + u (P2 - P1). The intersection of these two occurs when:          //
+//   N dot (P1 + u (P2 - P1)) = N dot P3.                                    //
+// Solving for u gives:                                                      //
+//         N dot (P3 - P1)                                                   //
+//   u = ------------------.                                                 //
+//         N dot (P2 - P1)                                                   //
+// If the denominator is 0 then N (the normal to the plane) is perpendicular //
+// to the line.  Thus the line is either parallel to the plane and there are //
+// no solutions or the line is on the plane in which case there are an infi- //
+// nite number of solutions.                                                 //
+//                                                                           //
+// The plane is given by three points pa, pb, and pc, e1 and e2 defines the  //
+// line. If u is non-zero, The intersection point (if exists) returns in ip. //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::planelineint(REAL* pa, REAL* pb, REAL* pc, REAL* e1, REAL* e2,
+                              REAL* ip, REAL* u)
+{
+  REAL n[3], det, det1;
+
+  // Calculate N.
+  facenormal(pa, pb, pc, n, 1, NULL);
+  // Calculate N dot (e2 - e1).
+  det = n[0] * (e2[0] - e1[0]) + n[1] * (e2[1] - e1[1])
+      + n[2] * (e2[2] - e1[2]);
+  if (det != 0.0) {
+    // Calculate N dot (pa - e1)
+    det1 = n[0] * (pa[0] - e1[0]) + n[1] * (pa[1] - e1[1])
+         + n[2] * (pa[2] - e1[2]);
+    *u = det1 / det;
+    ip[0] = e1[0] + *u * (e2[0] - e1[0]);
+    ip[1] = e1[1] + *u * (e2[1] - e1[1]);
+    ip[2] = e1[2] + *u * (e2[2] - e1[2]);
+  } else {
+    *u = 0.0;
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// linelineint()    Calculate the intersection(s) of two line segments.      //
+//                                                                           //
+// Calculate the line segment [P, Q] that is the shortest route between two  //
+// lines from A to B and C to D. Calculate also the values of tp and tq      //
+// where: P = A + tp (B - A), and Q = C + tq (D - C).                        //
+//                                                                           //
+// Return 1 if the line segment exists. Otherwise, return 0.                 //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::linelineint(REAL* A, REAL* B, REAL* C, REAL* D, REAL* P, 
+		            REAL* Q, REAL* tp, REAL* tq)
+{
+  REAL vab[3], vcd[3], vca[3];
+  REAL vab_vab, vcd_vcd, vab_vcd;
+  REAL vca_vab, vca_vcd;
+  REAL det, eps;
+  int i;
+
+  for (i = 0; i < 3; i++) {
+    vab[i] = B[i] - A[i];
+    vcd[i] = D[i] - C[i];
+    vca[i] = A[i] - C[i];
+  }
+
+  vab_vab = dot(vab, vab);
+  vcd_vcd = dot(vcd, vcd);
+  vab_vcd = dot(vab, vcd);
+
+  det = vab_vab * vcd_vcd - vab_vcd * vab_vcd;
+  // Round the result.
+  eps = det / (fabs(vab_vab * vcd_vcd) + fabs(vab_vcd * vab_vcd));
+  if (eps < b->epsilon) {
+    return 0;
+  }
+
+  vca_vab = dot(vca, vab);
+  vca_vcd = dot(vca, vcd);
+
+  *tp = (vcd_vcd * (- vca_vab) + vab_vcd * vca_vcd) / det;
+  *tq = (vab_vcd * (- vca_vab) + vab_vab * vca_vcd) / det;
+
+  for (i = 0; i < 3; i++) P[i] = A[i] + (*tp) * vab[i];
+  for (i = 0; i < 3; i++) Q[i] = C[i] + (*tq) * vcd[i];
+
+  return 1;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// tetprismvol()    Calculate the volume of a tetrahedral prism in 4D.       //
+//                                                                           //
+// A tetrahedral prism is a convex uniform polychoron (four dimensional poly-//
+// tope). It has 6 polyhedral cells: 2 tetrahedra connected by 4 triangular  //
+// prisms. It has 14 faces: 8 triangular and 6 square. It has 16 edges and 8 //
+// vertices. (Wikipedia).                                                    //
+//                                                                           //
+// Let 'p0', ..., 'p3' be four affinely independent points in R^3. They form //
+// the lower tetrahedral facet of the prism.  The top tetrahedral facet is   //
+// formed by four vertices, 'p4', ..., 'p7' in R^4, which is obtained by     //
+// lifting each vertex of the lower facet into R^4 by a weight (height).  A  //
+// canonical choice of the weights is the square of Euclidean norm of of the //
+// points (vectors).                                                         //
+//                                                                           //
+//                                                                           //
+// The return value is (4!) 24 times of the volume of the tetrahedral prism. //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+REAL tetgenmesh::tetprismvol(REAL* p0, REAL* p1, REAL* p2, REAL* p3)
+{
+  REAL *p4, *p5, *p6, *p7;
+  REAL w4, w5, w6, w7;
+  REAL vol[4];
+
+  p4 = p0;
+  p5 = p1;
+  p6 = p2;
+  p7 = p3;
+
+  // TO DO: these weights can be pre-calculated!
+  w4 = dot(p0, p0);
+  w5 = dot(p1, p1);
+  w6 = dot(p2, p2);
+  w7 = dot(p3, p3);
+
+  // Calculate the volume of the tet-prism.
+  vol[0] = orient4d(p5, p6, p4, p3, p7, w5, w6, w4, 0, w7);
+  vol[1] = orient4d(p3, p6, p2, p0, p1,  0, w6,  0, 0,  0);
+  vol[2] = orient4d(p4, p6, p3, p0, p1, w4, w6,  0, 0,  0);
+  vol[3] = orient4d(p6, p5, p4, p3, p1, w6, w5, w4, 0,  0);
+
+  return fabs(vol[0]) + fabs(vol[1]) + fabs(vol[2]) + fabs(vol[3]);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// calculateabovepoint()    Calculate a point above a facet in 'dummypoint'. //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+bool tetgenmesh::calculateabovepoint(arraypool *facpoints, point *ppa,
+                                     point *ppb, point *ppc)
+{
+  point *ppt, pa, pb, pc;
+  REAL v1[3], v2[3], n[3];
+  REAL lab, len, A, area;
+  REAL x, y, z;
+  int i;
+
+  ppt = (point *) fastlookup(facpoints, 0);
+  pa = *ppt; // a is the first point.
+  pb = pc = NULL; // Avoid compiler warnings.
+
+  // Get a point b s.t. the length of [a, b] is maximal.
+  lab = 0;
+  for (i = 1; i < facpoints->objects; i++) {
+    ppt = (point *) fastlookup(facpoints, i);
+    x = (*ppt)[0] - pa[0];
+    y = (*ppt)[1] - pa[1];
+    z = (*ppt)[2] - pa[2];
+    len = x * x + y * y + z * z;
+    if (len > lab) {
+      lab = len;
+      pb = *ppt;
+    }
+  }
+  lab = sqrt(lab);
+  if (lab == 0) {
+    if (!b->quiet) {
+      printf("Warning:  All points of a facet are coincident with %d.\n",
+        pointmark(pa));
+    }
+    return false;
+  }
+
+  // Get a point c s.t. the area of [a, b, c] is maximal.
+  v1[0] = pb[0] - pa[0];
+  v1[1] = pb[1] - pa[1];
+  v1[2] = pb[2] - pa[2];
+  A = 0;
+  for (i = 1; i < facpoints->objects; i++) {
+    ppt = (point *) fastlookup(facpoints, i);
+    v2[0] = (*ppt)[0] - pa[0];
+    v2[1] = (*ppt)[1] - pa[1];
+    v2[2] = (*ppt)[2] - pa[2];
+    cross(v1, v2, n);
+    area = dot(n, n);
+    if (area > A) {
+      A = area;
+      pc = *ppt;
+    }
+  }
+  if (A == 0) {
+    // All points are collinear. No above point.
+    if (!b->quiet) {
+      printf("Warning:  All points of a facet are collinaer with [%d, %d].\n",
+        pointmark(pa), pointmark(pb));
+    }
+    return false;
+  }
+
+  // Calculate an above point of this facet.
+  facenormal(pa, pb, pc, n, 1, NULL);
+  len = sqrt(dot(n, n));
+  n[0] /= len;
+  n[1] /= len;
+  n[2] /= len;
+  lab /= 2.0; // Half the maximal length.
+  dummypoint[0] = pa[0] + lab * n[0];
+  dummypoint[1] = pa[1] + lab * n[1];
+  dummypoint[2] = pa[2] + lab * n[2];
+
+  if (ppa != NULL) {
+    // Return the three points.
+    *ppa = pa;
+    *ppb = pb;
+    *ppc = pc;
+  }
+
+  return true;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Calculate an above point. It lies above the plane containing  the subface //
+//   [a,b,c], and save it in dummypoint. Moreover, the vector pa->dummypoint //
+//   is the normal of the plane.                                             //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::calculateabovepoint4(point pa, point pb, point pc, point pd)
+{
+  REAL n1[3], n2[3], *norm;
+  REAL len, len1, len2;
+
+  // Select a base.
+  facenormal(pa, pb, pc, n1, 1, NULL);
+  len1 = sqrt(dot(n1, n1));
+  facenormal(pa, pb, pd, n2, 1, NULL);
+  len2 = sqrt(dot(n2, n2));
+  if (len1 > len2) {
+    norm = n1;
+    len = len1;
+  } else {
+    norm = n2;
+    len = len2;
+  }
+  norm[0] /= len;
+  norm[1] /= len;
+  norm[2] /= len;
+  len = distance(pa, pb);
+  dummypoint[0] = pa[0] + len * norm[0];
+  dummypoint[1] = pa[1] + len * norm[1];
+  dummypoint[2] = pa[2] + len * norm[2];
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// report_overlapping_facets()    Report two overlapping facets.             //
+//                                                                           //
+// Two subfaces, f1 [a, b, c] and f2 [a, b, d], share the same edge [a, b].  //
+// 'dihedang' is the dihedral angle between these two facets. It must less   //
+// than the variable 'b->facet_overlap_angle_tol'.                           //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::report_overlapping_facets(face *f1, face *f2, REAL dihedang)
+{
+  point pa, pb, pc, pd;
+
+  pa = sorg(*f1);
+  pb = sdest(*f1);
+  pc = sapex(*f1);
+  pd = sapex(*f2);
+
+  if (pc != pd) {
+    printf("Found two %s self-intersecting facets.\n", 
+           dihedang > 0 ? "nearly" : "exactly");
+    printf("  1st: [%d, %d, %d] #%d\n", 
+	       pointmark(pa), pointmark(pb), pointmark(pc), shellmark(*f1));
+    printf("  2nd: [%d, %d, %d] #%d\n",
+	       pointmark(pa), pointmark(pb), pointmark(pd), shellmark(*f2));
+    if (dihedang > 0) {
+      printf("The dihedral angle between them is %g degree.\n", 
+             dihedang / PI * 180.0);
+      printf("Hint:  You may use -p/# to decrease the dihedral angle");
+      printf("  tolerance %g (degree).\n", b->facet_overlap_ang_tol);
+    }
+  } else {
+    if (shellmark(*f1) != shellmark(*f2)) {
+      // Two identical faces from two different facet.
+      printf("Found two overlapping facets.\n");
+    } else {
+      printf("Found two duplicated facets.\n");
+    }
+    printf("  1st: [%d, %d, %d] #%d\n", 
+	       pointmark(pa), pointmark(pb), pointmark(pc), shellmark(*f1));
+    printf("  2nd: [%d, %d, %d] #%d\n",
+	       pointmark(pa), pointmark(pb), pointmark(pd), shellmark(*f2));
+  }
+
+  terminatetetgen(this, 3);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// report_selfint_edge()    Report a self-intersection at an edge.           //
+//                                                                           //
+// The edge 'e1'->'e2' and the tetrahedron 'itet' intersect. 'dir' indicates //
+// that the edge intersects the tet at its origin vertex (ACROSSVERTEX), or  //
+// its current face (ACROSSFACE), or its current edge (ACROSSEDGE).          //
+// If 'iedge' is not NULL, it is either a segment or a subface that contains //
+// the edge 'e1'->'e2'.  It is used to report the geometry entity.           //
+//                                                                           //
+// Since it is a self-intersection, the vertex, edge or face of 'itet' that  //
+// is intersecting with this edge must be an input vertex, a segment, or a   //
+// subface, respectively.                                                    //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::report_selfint_edge(point e1, point e2, face *iedge,
+  triface* itet, enum interresult dir)
+{
+  point forg = NULL, fdest = NULL, fapex = NULL;
+  int etype = 0, geomtag = 0, facemark = 0;
+
+  if (iedge != NULL) {
+    if (iedge->sh[5] != NULL) {
+      etype = 2;  // A subface
+      forg = e1;
+      fdest = e2;
+      fapex = sapex(*iedge);
+      facemark = shellmark(*iedge);
+    } else {
+      etype = 1;  // A segment
+      forg = farsorg(*iedge);
+      fdest = farsdest(*iedge);
+      // Get a facet containing this segment.
+      face parentsh;
+      spivot(*iedge, parentsh);
+      if (parentsh.sh != NULL) {
+        facemark = shellmark(parentsh);
+      }
+    }
+    geomtag = shellmark(*iedge);
+  }
+
+  if (dir == SHAREEDGE) {
+    // Two edges (segments) are coincide.
+    face colseg;
+    tsspivot1(*itet, colseg);
+    if (etype == 1) {
+      if (colseg.sh != iedge->sh) {
+        face parentsh;
+        spivot(colseg, parentsh);
+        printf("PLC Error:  Two segments are overlapping.\n");
+        printf("  Segment 1: [%d, %d] #%d (%d)\n", pointmark(sorg(colseg)),
+               pointmark(sdest(colseg)), shellmark(colseg),
+               parentsh.sh ? shellmark(parentsh) : 0);
+        printf("  Segment 2: [%d, %d] #%d (%d)\n", pointmark(forg),
+               pointmark(fdest), geomtag, facemark);
+      } else {
+        // Two identical segments. Why report it?
+        terminatetetgen(this, 2); 
+      }
+    } else if (etype == 2) {
+      printf("PLC Error:  A segment lies in a facet.\n");
+      printf("  Segment: [%d, %d] #%d\n", pointmark(sorg(colseg)),
+             pointmark(sdest(colseg)), shellmark(colseg));
+      printf("  Facet:   [%d,%d,%d] #%d\n", pointmark(forg), 
+             pointmark(fdest), pointmark(fapex), geomtag);
+    }
+  } else if (dir == SHAREFACE) {
+    // Two triangles (subfaces) are coincide.
+	face colface;
+    tspivot(*itet, colface);
+	if (etype == 2) {
+	  if (colface.sh != iedge->sh) {
+	    printf("PLC Error:  Two facets are overlapping.\n");
+		printf("  Facet 1:  [%d,%d,%d] #%d\n", pointmark(forg), 
+               pointmark(fdest), pointmark(fapex), geomtag);
+		printf("  Facet 2:  [%d,%d,%d] #%d\n", pointmark(sorg(colface)), 
+             pointmark(sdest(colface)), pointmark(sapex(colface)), 
+			 shellmark(colface));
+	  } else {
+	    // Two identical subfaces. Why report it?
+        terminatetetgen(this, 2); 
+	  }
+	} else {
+	  terminatetetgen(this, 2);
+	}
+  } else if (dir == ACROSSVERT) {
+    point pp = dest(*itet);
+    if ((pointtype(pp) == RIDGEVERTEX) || (pointtype(pp) == FACETVERTEX)
+        || (pointtype(pp) == VOLVERTEX)) {
+      if (etype == 1) {
+        printf("PLC Error:  A vertex lies in a segment.\n");
+        printf("  Vertex:  [%d] (%g,%g,%g).\n",pointmark(pp),pp[0],pp[1],pp[2]);
+        printf("  Segment: [%d, %d] #%d (%d)\n", pointmark(forg), 
+               pointmark(fdest), geomtag, facemark);
+      } else if (etype == 2) {
+        printf("PLC Error:  A vertex lies in a facet.\n");
+        printf("  Vertex: [%d] (%g,%g,%g).\n",pointmark(pp),pp[0],pp[1],pp[2]);
+        printf("  Facet:  [%d,%d,%d] #%d\n", pointmark(forg), pointmark(fdest),
+               pointmark(fapex), geomtag);
+      }
+    } else if (pointtype(pp) == FREESEGVERTEX) {
+      face parentseg, parentsh;
+      sdecode(point2sh(pp), parentseg);
+      spivot(parentseg, parentsh);
+      if (parentseg.sh != NULL) {
+        point p1 = farsorg(parentseg);
+        point p2 = farsdest(parentseg);
+        if (etype == 1) {
+          printf("PLC Error:  Two segments intersect at point (%g,%g,%g).\n",
+                 pp[0], pp[1], pp[2]);
+          printf("  Segment 1: [%d, %d], #%d (%d)\n", pointmark(forg), 
+                 pointmark(fdest), geomtag, facemark);
+          printf("  Segment 2: [%d, %d], #%d (%d)\n", pointmark(p1), 
+                 pointmark(p2), shellmark(parentseg),
+                 parentsh.sh ? shellmark(parentsh) : 0);
+        } else if (etype == 2) {
+          printf("PLC Error:  A segment and a facet intersect at point");
+          printf(" (%g,%g,%g).\n", pp[0], pp[1], pp[2]);
+          printf("  Segment: [%d, %d], #%d (%d)\n", pointmark(p1),
+                 pointmark(p2), shellmark(parentseg),
+                 parentsh.sh ? shellmark(parentsh) : 0);
+          printf("  Facet:   [%d,%d,%d] #%d\n", pointmark(forg), 
+                 pointmark(fdest), pointmark(fapex), geomtag);
+        }
+      } else {
+        terminatetetgen(this, 2); // Report a bug.
+      }
+    } else if (pointtype(pp) == FREEFACETVERTEX) {
+      face parentsh;
+      sdecode(point2sh(pp), parentsh);
+      if (parentsh.sh != NULL) {
+        point p1 = sorg(parentsh);
+        point p2 = sdest(parentsh);
+        point p3 = sapex(parentsh);
+        if (etype == 1) {
+          printf("PLC Error:  A segment and a facet intersect at point");
+          printf(" (%g,%g,%g).\n", pp[0], pp[1], pp[2]);
+          printf("  Segment : [%d, %d], #%d (%d)\n", pointmark(forg), 
+                 pointmark(fdest), geomtag, facemark);
+          printf("  Facet   : [%d, %d, %d]  #%d.\n", pointmark(p1),
+                 pointmark(p2), pointmark(p3), shellmark(parentsh));
+        } else if (etype == 2) {
+          printf("PLC Error:  Two facets intersect at point (%g,%g,%g).\n",
+                 pp[0], pp[1], pp[2]);
+          printf("  Facet 1: [%d, %d, %d] #%d.\n", pointmark(forg), 
+                 pointmark(fdest), pointmark(fapex), geomtag);
+          printf("  Facet 2: [%d, %d, %d] #%d.\n", pointmark(p1),
+                 pointmark(p2), pointmark(p3), shellmark(parentsh));
+        }
+      } else {
+        terminatetetgen(this, 2); // Report a bug.
+      }
+    } else if (pointtype(pp) == FREEVOLVERTEX) {
+      // This is not a PLC error. 
+      // We should shift the vertex.
+      // not down yet.
+      terminatetetgen(this, 2); // Report a bug.
+    } else {
+      terminatetetgen(this, 2); // Report a bug.
+    }
+    terminatetetgen(this, 3);
+  } else if (dir == ACROSSEDGE) {
+    if (issubseg(*itet)) {
+      face checkseg;
+      tsspivot1(*itet, checkseg);
+      face parentsh;
+      spivot(checkseg, parentsh);
+      // Calulcate the intersecting point.
+      point p1 = sorg(checkseg);
+      point p2 = sdest(checkseg);
+      REAL P[3], Q[3], tp = 0, tq = 0;
+      linelineint(e1, e2, p1, p2, P, Q, &tp, &tq);
+      if (etype == 1) {
+        printf("PLC Error:  Two segments intersect at point (%g,%g,%g).\n",
+               P[0], P[1], P[2]);
+        printf("  Segment 1: [%d, %d] #%d (%d)\n", pointmark(forg), 
+               pointmark(fdest), geomtag, facemark);
+        printf("  Segment 2: [%d, %d] #%d (%d)\n", pointmark(p1), 
+               pointmark(p2), shellmark(checkseg),
+               parentsh.sh ? shellmark(parentsh) : 0);
+      } else if (etype == 2) {
+        printf("PLC Error:  A segment and a facet intersect at point");
+        printf(" (%g,%g,%g).\n", P[0], P[1], P[2]);
+        printf("  Segment: [%d, %d] #%d (%d)\n", pointmark(p1), 
+               pointmark(p2), shellmark(checkseg),
+               parentsh.sh ? shellmark(parentsh) : 0);
+        printf("  Facet:   [%d, %d, %d] #%d.\n", pointmark(forg), 
+               pointmark(fdest), pointmark(fapex), geomtag);
+      }
+      terminatetetgen(this, 3);
+    }
+  } else if (dir == ACROSSFACE) {
+    if (issubface(*itet)) {
+      face checksh;
+      tspivot(*itet, checksh);
+      point p1 = sorg(checksh);
+      point p2 = sdest(checksh);
+      point p3 = sapex(checksh);
+      REAL ip[3], u = 0;
+      planelineint(p1, p2, p3, e1, e2, ip, &u);
+      if (etype == 1) {
+        printf("PLC Error:  A segment and a facet intersect at point");
+        printf(" (%g,%g,%g).\n", ip[0], ip[1], ip[2]);
+        printf("  Segment: [%d, %d] #%d (%d)\n", pointmark(forg), 
+               pointmark(fdest), geomtag, facemark);
+        printf("  Facet:   [%d, %d, %d] #%d.\n", pointmark(p1),
+               pointmark(p2), pointmark(p3), shellmark(checksh));
+      } else if (etype == 2) {
+        printf("PLC Error:  Two facets intersect at point (%g,%g,%g).\n",
+               ip[0], ip[1], ip[2]);
+        printf("  Facet 1: [%d, %d, %d] #%d.\n", pointmark(forg), 
+               pointmark(fdest), pointmark(fapex), geomtag);
+        printf("  Facet 2: [%d, %d, %d] #%d.\n", pointmark(p1),
+               pointmark(p2), pointmark(p3), shellmark(checksh));
+      }
+      terminatetetgen(this, 3);
+    }
+  } else {
+    // An unknown 'dir'.
+    terminatetetgen(this, 2);
+  }
+  return 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// report_selfint_face()    Report a self-intersection at a facet.           //
+//                                                                           //
+// The triangle with vertices 'p1', 'p2', and 'p3' intersects with the edge  //
+// of the tetrahedra 'iedge'. The intersection type is reported by 'intflag',//
+// 'types', and 'poss'.                                                      //
+//                                                                           //
+// This routine ASSUMES (1) the triangle (p1,p2,p3) must belong to a facet,  //
+// 'sface' is a subface of the same facet; and (2) 'iedge' must be either a  //
+// segment or an edge of another facet.                                      //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::report_selfint_face(point p1, point p2, point p3, face* sface,
+  triface* iedge, int intflag, int* types, int* poss)
+{
+  face iface;
+  point e1 = NULL, e2 = NULL, e3 = NULL;
+  int etype = 0, geomtag = 0, facemark = 0;
+
+  geomtag = shellmark(*sface);
+
+  if (issubface(*iedge)) {
+    tspivot(*iedge, iface);
+    e1 = sorg(iface);
+    e2 = sdest(iface);
+    e3 = sapex(iface);
+    etype = 2;
+    facemark = geomtag;
+  } else if (issubseg(*iedge)) {
+    tsspivot1(*iedge, iface);
+    e1 = farsorg(iface);
+    e2 = farsdest(iface);
+    etype = 1;
+    face parentsh;
+    spivot(iface, parentsh);
+    facemark = shellmark(parentsh);
+  } else {
+    terminatetetgen(this, 2);
+  }
+
+  if (intflag == 2) {
+    // The triangle and the edge intersect only at one point.
+    REAL ip[3], u = 0;
+    planelineint(p1, p2, p3, e1, e2, ip, &u);
+    if ((types[0] == (int) ACROSSFACE) ||
+        (types[0] == (int) ACROSSEDGE)) {
+      // The triangle and the edge intersect in their interiors. 
+      if (etype == 1) {
+        printf("PLC Error:  A segment and a facet intersect at point");
+        printf(" (%g,%g,%g).\n", ip[0], ip[1], ip[2]);
+        printf("  Segment: [%d,%d] #%d (%d)\n", pointmark(e1), pointmark(e2),
+               shellmark(iface), facemark);
+        printf("  Facet:   [%d,%d,%d] #%d\n", pointmark(p1), 
+               pointmark(p2), pointmark(p3), geomtag);
+      } else {
+        printf("PLC Error:  Two facets intersect at point");
+        printf(" (%g,%g,%g).\n", ip[0], ip[1], ip[2]);
+        printf("  Facet 1: [%d,%d,%d] #%d\n", pointmark(e1), pointmark(e2),
+               pointmark(sorg(iface)), shellmark(iface));
+        printf("  Facet 2: [%d,%d,%d] #%d\n", pointmark(p1), 
+               pointmark(p2), pointmark(p3), geomtag);
+      }
+    } else if (types[0] == (int) ACROSSVERT) {
+      // A vertex of the triangle and the edge intersect.
+      point crosspt = NULL;
+      if (poss[0] == 0) {
+        crosspt = p1;
+      } else if (poss[0] == 1) {
+        crosspt = p2;
+      } else if (poss[0] == 2) {
+        crosspt = p3;
+      } else {
+        terminatetetgen(this, 2);
+      }
+      if (!issteinerpoint(crosspt)) {
+        if (etype == 1) {
+          printf("PLC Error:  A vertex and a segment intersect at (%g,%g,%g)\n",
+                 crosspt[0], crosspt[1], crosspt[2]);
+          printf("  Vertex:  #%d\n", pointmark(crosspt));
+          printf("  Segment: [%d,%d] #%d (%d)\n", pointmark(e1), pointmark(e2),
+                 shellmark(iface), facemark);
+        } else {
+          printf("PLC Error:  A vertex and a facet intersect at (%g,%g,%g)\n",
+                 crosspt[0], crosspt[1], crosspt[2]);
+          printf("  Vertex:  #%d\n", pointmark(crosspt));
+          printf("  Facet:   [%d,%d,%d] #%d\n", pointmark(p1), 
+                 pointmark(p2), pointmark(p3), geomtag);
+        }
+      } else {
+        // It is a Steiner point. To be processed.
+        terminatetetgen(this, 2);
+      }
+    } else if ((types[0] == (int) TOUCHFACE) ||
+               (types[0] == (int) TOUCHEDGE)) {
+      // The triangle and a vertex of the edge intersect.
+      point touchpt = NULL;
+      if (poss[1] == 0) {
+        touchpt = org(*iedge);
+      } else if (poss[1] == 1) {
+        touchpt = dest(*iedge);
+      } else {
+        terminatetetgen(this, 2);
+      }
+      if (!issteinerpoint(touchpt)) {
+        printf("PLC Error:  A vertex and a facet intersect at (%g,%g,%g)\n",
+               touchpt[0], touchpt[1], touchpt[2]);
+        printf("  Vertex:  #%d\n", pointmark(touchpt));
+        printf("  Facet:   [%d,%d,%d] #%d\n", pointmark(p1), 
+               pointmark(p2), pointmark(p3), geomtag);
+      } else {
+        // It is a Steiner point. To be processed.
+        terminatetetgen(this, 2);
+      }
+    } else if (types[0] == (int) SHAREVERT) {
+      terminatetetgen(this, 2);
+    } else {
+      terminatetetgen(this, 2);
+    }
+  } else if (intflag == 4) {
+    if (types[0] == (int) SHAREFACE) {
+      printf("PLC Error:  Two facets are overlapping.\n");
+      printf("  Facet 1:   [%d,%d,%d] #%d\n", pointmark(e1), 
+             pointmark(e2), pointmark(e3), facemark);
+      printf("  Facet 2:   [%d,%d,%d] #%d\n", pointmark(p1), 
+             pointmark(p2), pointmark(p3), geomtag);
+    } else {
+      terminatetetgen(this, 2);
+    }
+  } else {
+    terminatetetgen(this, 2);
+  }
+
+  terminatetetgen(this, 3);
+  return 0;
+}
+
+////                                                                       ////
+////                                                                       ////
+//// geom_cxx /////////////////////////////////////////////////////////////////
+
+//// flip_cxx /////////////////////////////////////////////////////////////////
+////                                                                       ////
+////                                                                       ////
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// flip23()    Perform a 2-to-3 flip (face-to-edge flip).                    //
+//                                                                           //
+// 'fliptets' is an array of three tets (handles), where the [0] and [1] are  //
+// [a,b,c,d] and [b,a,c,e].  The three new tets: [e,d,a,b], [e,d,b,c], and   //
+// [e,d,c,a] are returned in [0], [1], and [2] of 'fliptets'.  As a result,  //
+// The face [a,b,c] is removed, and the edge [d,e] is created.               //
+//                                                                           //
+// If 'hullflag' > 0, hull tets may be involved in this flip, i.e., one of   //
+// the five vertices may be 'dummypoint'. There are two canonical cases:     //
+//   (1) d is 'dummypoint', then all three new tets are hull tets.  If e is  //
+//       'dummypoint', we reconfigure e to d, i.e., turn it up-side down.    //
+//   (2) c is 'dummypoint', then two new tets: [e,d,b,c] and [e,d,c,a], are  //
+//       hull tets. If a or b is 'dummypoint', we reconfigure it to c, i.e., //
+//       rotate the three input tets counterclockwisely (right-hand rule)    //
+//       until a or b is in c's position.                                    //
+//                                                                           //
+// If 'fc->enqflag' is set, convex hull faces will be queued for flipping.   //
+// In particular, if 'fc->enqflag' is 1, it is called by incrementalflip()   //
+// after the insertion of a new point.  It is assumed that 'd' is the new    //
+// point. IN this case, only link faces of 'd' are queued.                   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::flip23(triface* fliptets, int hullflag, flipconstraints *fc)
+{
+  triface topcastets[3], botcastets[3];
+  triface newface, casface;
+  point pa, pb, pc, pd, pe;
+  REAL attrib, volume;
+  int dummyflag = 0;  // range = {-1, 0, 1, 2}.
+  int i;
+
+  if (hullflag > 0) {
+    // Check if e is dummypoint.
+    if (oppo(fliptets[1]) == dummypoint) {
+      // Swap the two old tets.
+      newface = fliptets[0];
+      fliptets[0] = fliptets[1];
+      fliptets[1] = newface;
+      dummyflag = -1;  // d is dummypoint.
+    } else {
+      // Check if either a or b is dummypoint.
+      if (org(fliptets[0]) == dummypoint) {
+        dummyflag = 1; // a is dummypoint.
+        enextself(fliptets[0]);
+        eprevself(fliptets[1]);
+      } else if (dest(fliptets[0]) == dummypoint) {
+        dummyflag = 2; // b is dummypoint.
+        eprevself(fliptets[0]);
+        enextself(fliptets[1]);
+      } else {
+        dummyflag = 0; // either c or d may be dummypoint.
+      }
+    }
+  }
+
+  pa =  org(fliptets[0]);
+  pb = dest(fliptets[0]);
+  pc = apex(fliptets[0]);
+  pd = oppo(fliptets[0]);
+  pe = oppo(fliptets[1]);
+
+  flip23count++;
+
+  // Get the outer boundary faces.
+  for (i = 0; i < 3; i++) {
+    fnext(fliptets[0], topcastets[i]);
+    enextself(fliptets[0]);
+  }
+  for (i = 0; i < 3; i++) {
+    fnext(fliptets[1], botcastets[i]);
+    eprevself(fliptets[1]);
+  }
+
+  // Re-use fliptets[0] and fliptets[1].
+  fliptets[0].ver = 11;
+  fliptets[1].ver = 11;
+  setelemmarker(fliptets[0].tet, 0); // Clear all flags.
+  setelemmarker(fliptets[1].tet, 0);
+  // NOTE: the element attributes and volume constraint remain unchanged.
+  if (checksubsegflag) {
+    // Dealloc the space to subsegments.
+    if (fliptets[0].tet[8] != NULL) {
+      tet2segpool->dealloc((shellface *) fliptets[0].tet[8]);
+      fliptets[0].tet[8] = NULL;
+    }
+    if (fliptets[1].tet[8] != NULL) {
+      tet2segpool->dealloc((shellface *) fliptets[1].tet[8]);
+      fliptets[1].tet[8] = NULL;
+    }
+  }
+  if (checksubfaceflag) {
+    // Dealloc the space to subfaces.
+    if (fliptets[0].tet[9] != NULL) {
+      tet2subpool->dealloc((shellface *) fliptets[0].tet[9]);
+      fliptets[0].tet[9] = NULL;
+    }
+    if (fliptets[1].tet[9] != NULL) {
+      tet2subpool->dealloc((shellface *) fliptets[1].tet[9]);
+      fliptets[1].tet[9] = NULL;
+    }
+  }
+  // Create a new tet.
+  maketetrahedron(&(fliptets[2]));
+  // The new tet have the same attributes from the old tet.
+  for (i = 0; i < numelemattrib; i++) {
+    attrib = elemattribute(fliptets[0].tet, i);
+    setelemattribute(fliptets[2].tet, i, attrib);
+  }
+  if (b->varvolume) {
+    volume = volumebound(fliptets[0].tet);
+    setvolumebound(fliptets[2].tet, volume);
+  }
+
+  if (hullflag > 0) {
+    // Check if d is dummytet.
+    if (pd != dummypoint) {
+      setvertices(fliptets[0], pe, pd, pa, pb); // [e,d,a,b] *
+      setvertices(fliptets[1], pe, pd, pb, pc); // [e,d,b,c] *
+      // Check if c is dummypoint.
+      if (pc != dummypoint) {
+        setvertices(fliptets[2], pe, pd, pc, pa);  // [e,d,c,a] *
+      } else {
+        setvertices(fliptets[2], pd, pe, pa, pc); // [d,e,a,c]
+        esymself(fliptets[2]);                    // [e,d,c,a] *
+      }
+      // The hullsize does not change.
+    } else {
+      // d is dummypoint.
+      setvertices(fliptets[0], pa, pb, pe, pd); // [a,b,e,d]
+      setvertices(fliptets[1], pb, pc, pe, pd); // [b,c,e,d]
+      setvertices(fliptets[2], pc, pa, pe, pd); // [c,a,e,d]
+      // Adjust the faces to [e,d,a,b], [e,d,b,c], [e,d,c,a] *
+      for (i = 0; i < 3; i++) {
+        eprevesymself(fliptets[i]);
+        enextself(fliptets[i]);
+      }
+      // We deleted one hull tet, and created three hull tets.
+      hullsize += 2;
+    }
+  } else {
+    setvertices(fliptets[0], pe, pd, pa, pb); // [e,d,a,b] *
+    setvertices(fliptets[1], pe, pd, pb, pc); // [e,d,b,c] *
+    setvertices(fliptets[2], pe, pd, pc, pa); // [e,d,c,a] *
+  }
+
+  if (fc->remove_ndelaunay_edge) { // calc_tetprism_vol
+    REAL volneg[2], volpos[3], vol_diff;
+    if (pd != dummypoint) {
+      if (pc != dummypoint) {
+        volpos[0] = tetprismvol(pe, pd, pa, pb);
+        volpos[1] = tetprismvol(pe, pd, pb, pc);
+        volpos[2] = tetprismvol(pe, pd, pc, pa);
+        volneg[0] = tetprismvol(pa, pb, pc, pd);
+        volneg[1] = tetprismvol(pb, pa, pc, pe);
+      } else { // pc == dummypoint
+        volpos[0] = tetprismvol(pe, pd, pa, pb);
+        volpos[1] = 0.;
+        volpos[2] = 0.;
+        volneg[0] = 0.;
+        volneg[1] = 0.;
+      }
+    } else { // pd == dummypoint.
+      volpos[0] = 0.;
+      volpos[1] = 0.;
+      volpos[2] = 0.;
+      volneg[0] = 0.;
+      volneg[1] = tetprismvol(pb, pa, pc, pe);
+    }
+    vol_diff = volpos[0] + volpos[1] + volpos[2] - volneg[0] - volneg[1];
+    fc->tetprism_vol_sum  += vol_diff; // Update the total sum.
+  }
+
+  // Bond three new tets together.
+  for (i = 0; i < 3; i++) {
+    esym(fliptets[i], newface);
+    bond(newface, fliptets[(i + 1) % 3]);
+  }
+  // Bond to top outer boundary faces (at [a,b,c,d]).
+  for (i = 0; i < 3; i++) {
+    eorgoppo(fliptets[i], newface); // At edges [b,a], [c,b], [a,c].
+    bond(newface, topcastets[i]);
+  }
+  // Bond bottom outer boundary faces (at [b,a,c,e]).
+  for (i = 0; i < 3; i++) {
+    edestoppo(fliptets[i], newface); // At edges [a,b], [b,c], [c,a].
+    bond(newface, botcastets[i]);
+  }
+
+  if (checksubsegflag) {
+    // Bond subsegments if there are.
+    // Each new tet has 5 edges to be checked (except the edge [e,d]). 
+    face checkseg;
+    // The middle three: [a,b], [b,c], [c,a].
+    for (i = 0; i < 3; i++) {      
+      if (issubseg(topcastets[i])) {
+        tsspivot1(topcastets[i], checkseg);
+        eorgoppo(fliptets[i], newface);
+        tssbond1(newface, checkseg);
+        sstbond1(checkseg, newface);
+        if (fc->chkencflag & 1) {
+          enqueuesubface(badsubsegs, &checkseg);
+        }
+      }
+    }
+    // The top three: [d,a], [d,b], [d,c]. Two tets per edge.
+    for (i = 0; i < 3; i++) {
+      eprev(topcastets[i], casface);      
+      if (issubseg(casface)) {
+        tsspivot1(casface, checkseg);
+        enext(fliptets[i], newface);
+        tssbond1(newface, checkseg);
+        sstbond1(checkseg, newface);
+        esym(fliptets[(i + 2) % 3], newface);
+        eprevself(newface);
+        tssbond1(newface, checkseg);
+        sstbond1(checkseg, newface);
+        if (fc->chkencflag & 1) {
+          enqueuesubface(badsubsegs, &checkseg);
+        }
+      }
+    }
+    // The bot three: [a,e], [b,e], [c,e]. Two tets per edge.
+    for (i = 0; i < 3; i++) {
+      enext(botcastets[i], casface);
+      if (issubseg(casface)) {
+        tsspivot1(casface, checkseg);
+        eprev(fliptets[i], newface);
+        tssbond1(newface, checkseg);
+        sstbond1(checkseg, newface);
+        esym(fliptets[(i + 2) % 3], newface);
+        enextself(newface);
+        tssbond1(newface, checkseg);
+        sstbond1(checkseg, newface);
+        if (fc->chkencflag & 1) {
+          enqueuesubface(badsubsegs, &checkseg);
+        }
+      }
+    }
+  } // if (checksubsegflag)
+
+  if (checksubfaceflag) {
+    // Bond 6 subfaces if there are.
+    face checksh;
+    for (i = 0; i < 3; i++) {      
+      if (issubface(topcastets[i])) {
+        tspivot(topcastets[i], checksh);
+        eorgoppo(fliptets[i], newface);
+        sesymself(checksh);
+        tsbond(newface, checksh);
+        if (fc->chkencflag & 2) {
+          enqueuesubface(badsubfacs, &checksh);
+        }
+      }
+    }
+    for (i = 0; i < 3; i++) {
+      if (issubface(botcastets[i])) {
+        tspivot(botcastets[i], checksh);
+        edestoppo(fliptets[i], newface);
+        sesymself(checksh);
+        tsbond(newface, checksh);
+        if (fc->chkencflag & 2) {
+          enqueuesubface(badsubfacs, &checksh);
+        }
+      }
+    }
+  } // if (checksubfaceflag)
+
+  if (fc->chkencflag & 4) {
+    // Put three new tets into check list.
+    for (i = 0; i < 3; i++) {
+      enqueuetetrahedron(&(fliptets[i]));
+    }
+  }
+
+  // Update the point-to-tet map.
+  setpoint2tet(pa, (tetrahedron) fliptets[0].tet);
+  setpoint2tet(pb, (tetrahedron) fliptets[0].tet);
+  setpoint2tet(pc, (tetrahedron) fliptets[1].tet);
+  setpoint2tet(pd, (tetrahedron) fliptets[0].tet);
+  setpoint2tet(pe, (tetrahedron) fliptets[0].tet);
+
+  if (hullflag > 0) {
+    if (dummyflag != 0) {
+      // Restore the original position of the points (for flipnm()).
+      if (dummyflag == -1) { 
+        // Reverse the edge.
+        for (i = 0; i < 3; i++) {
+          esymself(fliptets[i]);
+        }
+        // Swap the last two new tets.
+        newface = fliptets[1];
+        fliptets[1] = fliptets[2];
+        fliptets[2] = newface;
+      } else {
+        // either a or b were swapped.
+        if (dummyflag == 1) {
+          // a is dummypoint.
+          newface = fliptets[0];
+          fliptets[0] = fliptets[2];
+          fliptets[2] = fliptets[1];
+          fliptets[1] = newface;
+        } else { // dummyflag == 2
+          // b is dummypoint.
+          newface = fliptets[0];
+          fliptets[0] = fliptets[1];
+          fliptets[1] = fliptets[2];
+          fliptets[2] = newface;
+        }
+      }
+    }
+  }
+
+  if (fc->enqflag > 0) {
+    // Queue faces which may be locally non-Delaunay.  
+    for (i = 0; i < 3; i++) {
+      eprevesym(fliptets[i], newface);
+      flippush(flipstack, &newface);
+    }
+    if (fc->enqflag > 1) {
+      for (i = 0; i < 3; i++) {
+        enextesym(fliptets[i], newface);
+        flippush(flipstack, &newface);
+      }
+    }
+  }
+
+  recenttet = fliptets[0];
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// flip32()    Perform a 3-to-2 flip (edge-to-face flip).                    //
+//                                                                           //
+// 'fliptets' is an array of three tets (handles),  which are [e,d,a,b],     //
+// [e,d,b,c], and [e,d,c,a].  The two new tets: [a,b,c,d] and [b,a,c,e] are  //
+// returned in [0] and [1] of 'fliptets'.  As a result, the edge [e,d] is    //
+// replaced by the face [a,b,c].                                             //
+//                                                                           //
+// If 'hullflag' > 0, hull tets may be involved in this flip, i.e., one of   //
+// the five vertices may be 'dummypoint'. There are two canonical cases:     //
+//   (1) d is 'dummypoint', then [a,b,c,d] is hull tet. If e is 'dummypoint',//
+//       we reconfigure e to d, i.e., turnover it.                           //
+//   (2) c is 'dummypoint' then both [a,b,c,d] and [b,a,c,e] are hull tets.  //
+//       If a or b is 'dummypoint', we reconfigure it to c, i.e., rotate the //
+//       three old tets counterclockwisely (right-hand rule) until a or b    //
+//       is in c's position.                                                 //
+//                                                                           //
+// If 'fc->enqflag' is set, convex hull faces will be queued for flipping.   //
+// In particular, if 'fc->enqflag' is 1, it is called by incrementalflip()   //
+// after the insertion of a new point.  It is assumed that 'a' is the new    //
+// point. In this case, only link faces of 'a' are queued.                   //
+//                                                                           //
+// If 'checksubfaceflag' is on (global variable), and assume [e,d] is not a  //
+// segment. There may be two (interior) subfaces sharing at [e,d], which are //
+// [e,d,p] and [e,d,q], where the pair (p,q) may be either (a,b), or (b,c),  //
+// or (c,a)  In such case, a 2-to-2 flip is performed on these two subfaces  //
+// and two new subfaces [p,q,e] and [p,q,d] are created. They are inserted   //
+// back into the tetrahedralization.                                         //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::flip32(triface* fliptets, int hullflag, flipconstraints *fc)
+{
+  triface topcastets[3], botcastets[3];
+  triface newface, casface;
+  face flipshs[3]; 
+  face checkseg; 
+  point pa, pb, pc, pd, pe;
+  REAL attrib, volume;
+  int dummyflag = 0;  // Rangle = {-1, 0, 1, 2}
+  int spivot = -1, scount = 0; // for flip22()
+  int t1ver; 
+  int i, j;
+
+  if (hullflag > 0) {
+    // Check if e is 'dummypoint'.
+    if (org(fliptets[0]) == dummypoint) {
+      // Reverse the edge.
+      for (i = 0; i < 3; i++) {
+        esymself(fliptets[i]);
+      }
+      // Swap the last two tets.
+      newface = fliptets[1];
+      fliptets[1] = fliptets[2];
+      fliptets[2] = newface;
+      dummyflag = -1; // e is dummypoint.
+    } else {
+      // Check if a or b is the 'dummypoint'.
+      if (apex(fliptets[0]) == dummypoint) { 
+        dummyflag = 1;  // a is dummypoint.
+        newface = fliptets[0];
+        fliptets[0] = fliptets[1];
+        fliptets[1] = fliptets[2];
+        fliptets[2] = newface;
+      } else if (apex(fliptets[1]) == dummypoint) {
+        dummyflag = 2;  // b is dummypoint.
+        newface = fliptets[0];
+        fliptets[0] = fliptets[2];
+        fliptets[2] = fliptets[1];
+        fliptets[1] = newface;
+      } else {
+        dummyflag = 0;  // either c or d may be dummypoint.
+      }
+    }
+  }
+
+  pa = apex(fliptets[0]);
+  pb = apex(fliptets[1]);
+  pc = apex(fliptets[2]);
+  pd = dest(fliptets[0]);
+  pe = org(fliptets[0]);
+
+  flip32count++;
+
+  // Get the outer boundary faces.
+  for (i = 0; i < 3; i++) {
+    eorgoppo(fliptets[i], casface);
+    fsym(casface, topcastets[i]);
+  }
+  for (i = 0; i < 3; i++) {
+    edestoppo(fliptets[i], casface);
+    fsym(casface, botcastets[i]);
+  }
+
+  if (checksubfaceflag) {
+    // Check if there are interior subfaces at the edge [e,d].
+    for (i = 0; i < 3; i++) {
+      tspivot(fliptets[i], flipshs[i]);
+      if (flipshs[i].sh != NULL) {
+        // Found an interior subface.
+        stdissolve(flipshs[i]); // Disconnect the sub-tet bond.
+        scount++;
+      } else {
+        spivot = i;
+      }
+    }
+  }
+
+  // Re-use fliptets[0] and fliptets[1].
+  fliptets[0].ver = 11;
+  fliptets[1].ver = 11;
+  setelemmarker(fliptets[0].tet, 0); // Clear all flags.
+  setelemmarker(fliptets[1].tet, 0);
+  if (checksubsegflag) {
+    // Dealloc the space to subsegments.
+    if (fliptets[0].tet[8] != NULL) {
+      tet2segpool->dealloc((shellface *) fliptets[0].tet[8]);
+      fliptets[0].tet[8] = NULL;
+    }
+    if (fliptets[1].tet[8] != NULL) {
+      tet2segpool->dealloc((shellface *) fliptets[1].tet[8]);
+      fliptets[1].tet[8] = NULL;
+    }
+  }
+  if (checksubfaceflag) {
+    // Dealloc the space to subfaces.
+    if (fliptets[0].tet[9] != NULL) {
+      tet2subpool->dealloc((shellface *) fliptets[0].tet[9]);
+      fliptets[0].tet[9] = NULL;
+    }
+    if (fliptets[1].tet[9] != NULL) {
+      tet2subpool->dealloc((shellface *) fliptets[1].tet[9]);
+      fliptets[1].tet[9] = NULL;
+    }
+  }
+  if (checksubfaceflag) {
+    if (scount > 0) {
+      // The element attributes and volume constraint must be set correctly.
+      // There are two subfaces involved in this flip. The three tets are
+      //   separated into two different regions, one may be exterior. The
+      //   first region has two tets, and the second region has only one.
+      //   The two created tets must be in the same region as the first region. 
+      //   The element attributes and volume constraint must be set correctly.
+      //assert(spivot != -1);
+      // The tet fliptets[spivot] is in the first region.
+      for (j = 0; j < 2; j++) {
+        for (i = 0; i < numelemattrib; i++) {
+          attrib = elemattribute(fliptets[spivot].tet, i);
+          setelemattribute(fliptets[j].tet, i, attrib);
+        }
+        if (b->varvolume) {
+          volume = volumebound(fliptets[spivot].tet);
+          setvolumebound(fliptets[j].tet, volume);
+        }
+      }
+    }
+  }
+  // Delete an old tet.
+  tetrahedrondealloc(fliptets[2].tet);
+
+  if (hullflag > 0) {
+    // Check if c is dummypointc.
+    if (pc != dummypoint) {
+      // Check if d is dummypoint.
+      if (pd != dummypoint) {
+        // No hull tet is involved.
+      } else {
+        // We deleted three hull tets, and created one hull tet.
+        hullsize -= 2;
+      }
+      setvertices(fliptets[0], pa, pb, pc, pd);
+      setvertices(fliptets[1], pb, pa, pc, pe);
+    } else {
+      // c is dummypoint. The two new tets are hull tets.
+      setvertices(fliptets[0], pb, pa, pd, pc);
+      setvertices(fliptets[1], pa, pb, pe, pc);
+      // Adjust badc -> abcd.
+      esymself(fliptets[0]);
+      // Adjust abec -> bace.
+      esymself(fliptets[1]);
+      // The hullsize does not change.
+    }
+  } else {
+    setvertices(fliptets[0], pa, pb, pc, pd);
+    setvertices(fliptets[1], pb, pa, pc, pe);
+  }
+
+  if (fc->remove_ndelaunay_edge) { // calc_tetprism_vol
+    REAL volneg[3], volpos[2], vol_diff;
+    if (pc != dummypoint) {
+      if (pd != dummypoint) {
+        volneg[0] = tetprismvol(pe, pd, pa, pb);
+        volneg[1] = tetprismvol(pe, pd, pb, pc);
+        volneg[2] = tetprismvol(pe, pd, pc, pa);
+        volpos[0] = tetprismvol(pa, pb, pc, pd);
+        volpos[1] = tetprismvol(pb, pa, pc, pe);
+      } else { // pd == dummypoint
+        volneg[0] = 0.;
+        volneg[1] = 0.;
+        volneg[2] = 0.;
+        volpos[0] = 0.;
+        volpos[1] = tetprismvol(pb, pa, pc, pe);
+      }
+    } else { // pc == dummypoint.
+      volneg[0] = tetprismvol(pe, pd, pa, pb);
+      volneg[1] = 0.;
+      volneg[2] = 0.;
+      volpos[0] = 0.;
+      volpos[1] = 0.;
+    }
+    vol_diff = volpos[0] + volpos[1] - volneg[0] - volneg[1] - volneg[2];
+    fc->tetprism_vol_sum  += vol_diff; // Update the total sum.
+  }
+
+  // Bond abcd <==> bace.
+  bond(fliptets[0], fliptets[1]);
+  // Bond new faces to top outer boundary faces (at abcd).
+  for (i = 0; i < 3; i++) {
+    esym(fliptets[0], newface);
+    bond(newface, topcastets[i]);
+    enextself(fliptets[0]);
+  }
+  // Bond new faces to bottom outer boundary faces (at bace).
+  for (i = 0; i < 3; i++) {
+    esym(fliptets[1], newface);
+    bond(newface, botcastets[i]);
+    eprevself(fliptets[1]);
+  }
+
+  if (checksubsegflag) {
+    // Bond 9 segments to new (flipped) tets.
+    for (i = 0; i < 3; i++) { // edges a->b, b->c, c->a.      
+      if (issubseg(topcastets[i])) {
+        tsspivot1(topcastets[i], checkseg);
+        tssbond1(fliptets[0], checkseg);
+        sstbond1(checkseg, fliptets[0]);
+        tssbond1(fliptets[1], checkseg);
+        sstbond1(checkseg, fliptets[1]);
+        if (fc->chkencflag & 1) {
+          enqueuesubface(badsubsegs, &checkseg);
+        }
+      }
+      enextself(fliptets[0]);
+      eprevself(fliptets[1]);
+    }
+    // The three top edges.
+    for (i = 0; i < 3; i++) { // edges b->d, c->d, a->d.
+      esym(fliptets[0], newface);
+      eprevself(newface); 
+      enext(topcastets[i], casface);      
+      if (issubseg(casface)) {
+        tsspivot1(casface, checkseg);
+        tssbond1(newface, checkseg);
+        sstbond1(checkseg, newface);
+        if (fc->chkencflag & 1) {
+          enqueuesubface(badsubsegs, &checkseg);
+        }
+      }
+      enextself(fliptets[0]);
+    }
+    // The three bot edges.
+    for (i = 0; i < 3; i++) { // edges b<-e, c<-e, a<-e.
+      esym(fliptets[1], newface);
+      enextself(newface); 
+      eprev(botcastets[i], casface);
+      if (issubseg(casface)) {
+        tsspivot1(casface, checkseg);
+        tssbond1(newface, checkseg);
+        sstbond1(checkseg, newface);
+        if (fc->chkencflag & 1) {
+          enqueuesubface(badsubsegs, &checkseg);
+        }
+      }
+      eprevself(fliptets[1]);
+    }
+  } // if (checksubsegflag)
+
+  if (checksubfaceflag) {
+    face checksh;
+    // Bond the top three casing subfaces.
+    for (i = 0; i < 3; i++) { // At edges [b,a], [c,b], [a,c]
+      if (issubface(topcastets[i])) {
+        tspivot(topcastets[i], checksh);
+        esym(fliptets[0], newface); 
+        sesymself(checksh);
+        tsbond(newface, checksh);
+        if (fc->chkencflag & 2) {
+          enqueuesubface(badsubfacs, &checksh);
+        }
+      }
+      enextself(fliptets[0]);
+    }
+    // Bond the bottom three casing subfaces.
+    for (i = 0; i < 3; i++) { // At edges [a,b], [b,c], [c,a]
+      if (issubface(botcastets[i])) {
+        tspivot(botcastets[i], checksh);
+        esym(fliptets[1], newface); 
+        sesymself(checksh);
+        tsbond(newface, checksh);
+        if (fc->chkencflag & 2) {
+          enqueuesubface(badsubfacs, &checksh);
+        }
+      }
+      eprevself(fliptets[1]);
+    }
+
+    if (scount > 0) {
+      face flipfaces[2];
+      // Perform a 2-to-2 flip in subfaces.
+      flipfaces[0] = flipshs[(spivot + 1) % 3];
+      flipfaces[1] = flipshs[(spivot + 2) % 3];
+      sesymself(flipfaces[1]);
+      flip22(flipfaces, 0, fc->chkencflag);
+      // Connect the flipped subfaces to flipped tets.
+      // First go to the corresponding flipping edge.
+      //   Re-use top- and botcastets[0].
+      topcastets[0] = fliptets[0];
+      botcastets[0] = fliptets[1];
+      for (i = 0; i < ((spivot + 1) % 3); i++) {
+        enextself(topcastets[0]);
+        eprevself(botcastets[0]);
+      }
+      // Connect the top subface to the top tets.
+      esymself(topcastets[0]);
+      sesymself(flipfaces[0]);
+      // Check if there already exists a subface.
+      tspivot(topcastets[0], checksh);
+      if (checksh.sh == NULL) {
+        tsbond(topcastets[0], flipfaces[0]);
+        fsymself(topcastets[0]);
+        sesymself(flipfaces[0]);
+        tsbond(topcastets[0], flipfaces[0]);
+      } else {
+        // An invalid 2-to-2 flip. Report a bug.
+        terminatetetgen(this, 2); 
+      }
+      // Connect the bot subface to the bottom tets.
+      esymself(botcastets[0]);
+      sesymself(flipfaces[1]);
+      // Check if there already exists a subface.
+      tspivot(botcastets[0], checksh);
+      if (checksh.sh == NULL) {
+        tsbond(botcastets[0], flipfaces[1]);
+        fsymself(botcastets[0]);
+        sesymself(flipfaces[1]);
+        tsbond(botcastets[0], flipfaces[1]);
+      } else {
+        // An invalid 2-to-2 flip. Report a bug.
+        terminatetetgen(this, 2);  
+      }
+    } // if (scount > 0)
+  } // if (checksubfaceflag)
+
+  if (fc->chkencflag & 4) {
+    // Put two new tets into check list.
+    for (i = 0; i < 2; i++) {
+      enqueuetetrahedron(&(fliptets[i]));
+    }
+  }
+
+  setpoint2tet(pa, (tetrahedron) fliptets[0].tet);
+  setpoint2tet(pb, (tetrahedron) fliptets[0].tet);
+  setpoint2tet(pc, (tetrahedron) fliptets[0].tet);
+  setpoint2tet(pd, (tetrahedron) fliptets[0].tet);
+  setpoint2tet(pe, (tetrahedron) fliptets[1].tet);
+
+  if (hullflag > 0) {
+    if (dummyflag != 0) {
+      // Restore the original position of the points (for flipnm()).
+      if (dummyflag == -1) {
+        // e were dummypoint. Swap the two new tets.
+        newface = fliptets[0];
+        fliptets[0] = fliptets[1];
+        fliptets[1] = newface;
+      } else {
+        // a or b was dummypoint.
+        if (dummyflag == 1) {
+          eprevself(fliptets[0]);
+          enextself(fliptets[1]);
+        } else { // dummyflag == 2
+          enextself(fliptets[0]);
+          eprevself(fliptets[1]);
+        }
+      }
+    }
+  }
+  
+  if (fc->enqflag > 0) {
+    // Queue faces which may be locally non-Delaunay.
+    // pa = org(fliptets[0]); // 'a' may be a new vertex.
+    enextesym(fliptets[0], newface);
+    flippush(flipstack, &newface);
+    eprevesym(fliptets[1], newface);
+    flippush(flipstack, &newface);
+    if (fc->enqflag > 1) {
+      //pb = dest(fliptets[0]);
+      eprevesym(fliptets[0], newface);
+      flippush(flipstack, &newface);
+      enextesym(fliptets[1], newface);
+      flippush(flipstack, &newface);
+      //pc = apex(fliptets[0]);
+      esym(fliptets[0], newface);
+      flippush(flipstack, &newface);
+      esym(fliptets[1], newface);
+      flippush(flipstack, &newface);
+    }
+  }
+
+  recenttet = fliptets[0];
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// flip41()    Perform a 4-to-1 flip (Remove a vertex).                      //
+//                                                                           //
+// 'fliptets' is an array of four tetrahedra in the star of the removing     //
+// vertex 'p'. Let the four vertices in the star of p be a, b, c, and d. The //
+// four tets in 'fliptets' are: [p,d,a,b], [p,d,b,c], [p,d,c,a], and [a,b,c, //
+// p].  On return, 'fliptets[0]' is the new tet [a,b,c,d].                   //
+//                                                                           //
+// If 'hullflag' is set (> 0), one of the five vertices may be 'dummypoint'. //
+// The 'hullsize' may be changed.  Note that p may be dummypoint.  In this   //
+// case, four hull tets are replaced by one real tet.                        //
+//                                                                           //
+// If 'checksubface' flag is set (>0), it is possible that there are three   //
+// interior subfaces connecting at p.  If so, a 3-to-1 flip is performed to  //
+// to remove p from the surface triangulation.                               //
+//                                                                           //
+// If it is called by the routine incrementalflip(), we assume that d is the //
+// newly inserted vertex.                                                    //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::flip41(triface* fliptets, int hullflag, flipconstraints *fc)
+{
+  triface topcastets[3], botcastet;
+  triface newface, neightet;
+  face flipshs[4];
+  point pa, pb, pc, pd, pp;
+  int dummyflag = 0; // in {0, 1, 2, 3, 4}
+  int spivot = -1, scount = 0;
+  int t1ver; 
+  int i;
+
+  pa =  org(fliptets[3]);
+  pb = dest(fliptets[3]);
+  pc = apex(fliptets[3]);
+  pd = dest(fliptets[0]);
+  pp =  org(fliptets[0]); // The removing vertex.
+
+  flip41count++;
+
+  // Get the outer boundary faces.
+  for (i = 0; i < 3; i++) {
+    enext(fliptets[i], topcastets[i]);
+    fnextself(topcastets[i]); // [d,a,b,#], [d,b,c,#], [d,c,a,#]
+    enextself(topcastets[i]); // [a,b,d,#], [b,c,d,#], [c,a,d,#]
+  }
+  fsym(fliptets[3], botcastet); // [b,a,c,#]
+
+  if (checksubfaceflag) {
+    // Check if there are three subfaces at 'p'.
+    //   Re-use 'newface'.
+    for (i = 0; i < 3; i++) {
+      fnext(fliptets[3], newface); // [a,b,p,d],[b,c,p,d],[c,a,p,d].
+      tspivot(newface, flipshs[i]);
+      if (flipshs[i].sh != NULL) {
+        spivot = i; // Remember this subface.
+        scount++;
+      }
+      enextself(fliptets[3]);
+    }
+    if (scount > 0) {
+      // There are three subfaces connecting at p.
+      if (scount < 3) {
+        // The new subface is one of {[a,b,d], [b,c,d], [c,a,d]}.
+        // Go to the tet containing the three subfaces.
+        fsym(topcastets[spivot], neightet);
+        // Get the three subfaces connecting at p.
+        for (i = 0; i < 3; i++) {
+          esym(neightet, newface);
+          tspivot(newface, flipshs[i]);
+          eprevself(neightet);
+        }
+      } else {
+        spivot = 3; // The new subface is [a,b,c].
+      }
+    }
+  } // if (checksubfaceflag)
+
+
+  // Re-use fliptets[0] for [a,b,c,d].
+  fliptets[0].ver = 11;
+  setelemmarker(fliptets[0].tet, 0); // Clean all flags.
+  // NOTE: the element attributes and volume constraint remain unchanged.
+  if (checksubsegflag) {
+    // Dealloc the space to subsegments.
+    if (fliptets[0].tet[8] != NULL) {
+      tet2segpool->dealloc((shellface *) fliptets[0].tet[8]);
+      fliptets[0].tet[8] = NULL;
+    }
+  }
+  if (checksubfaceflag) {
+    // Dealloc the space to subfaces.
+    if (fliptets[0].tet[9] != NULL) {
+      tet2subpool->dealloc((shellface *) fliptets[0].tet[9]);
+      fliptets[0].tet[9] = NULL;
+    }
+  }
+  // Delete the other three tets.
+  for (i = 1; i < 4; i++) {
+    tetrahedrondealloc(fliptets[i].tet);
+  }
+
+  if (pp != dummypoint) {
+    // Mark the point pp as unused.
+    setpointtype(pp, UNUSEDVERTEX);
+    unuverts++;
+  }
+
+  // Create the new tet [a,b,c,d].
+  if (hullflag > 0) {
+    // One of the five vertices may be 'dummypoint'.
+    if (pa == dummypoint) {
+      // pa is dummypoint.
+      setvertices(fliptets[0], pc, pb, pd, pa);
+      esymself(fliptets[0]);  // [b,c,a,d]
+      eprevself(fliptets[0]); // [a,b,c,d]
+      dummyflag = 1;
+    } else if (pb == dummypoint) {
+      setvertices(fliptets[0], pa, pc, pd, pb);
+      esymself(fliptets[0]);  // [c,a,b,d]
+      enextself(fliptets[0]); // [a,b,c,d]
+      dummyflag = 2;
+    } else if (pc == dummypoint) {
+      setvertices(fliptets[0], pb, pa, pd, pc);
+      esymself(fliptets[0]);  // [a,b,c,d]
+      dummyflag = 3;
+    } else if (pd == dummypoint) {
+      setvertices(fliptets[0], pa, pb, pc, pd);
+      dummyflag = 4;
+    } else {
+      setvertices(fliptets[0], pa, pb, pc, pd);
+      if (pp == dummypoint) {
+        dummyflag = -1;
+      } else {
+        dummyflag = 0;
+      }
+    }
+    if (dummyflag > 0) {
+      // We deleted 3 hull tets, and create 1 hull tet.
+      hullsize -= 2;
+    } else if (dummyflag < 0) {
+      // We deleted 4 hull tets.
+      hullsize -= 4;
+      // meshedges does not change.
+    }
+  } else {
+    setvertices(fliptets[0], pa, pb, pc, pd);
+  }
+
+  if (fc->remove_ndelaunay_edge) { // calc_tetprism_vol
+    REAL volneg[4], volpos[1], vol_diff;
+    if (dummyflag > 0) {
+      if (pa == dummypoint) {
+        volneg[0] = 0.;
+        volneg[1] = tetprismvol(pp, pd, pb, pc);
+        volneg[2] = 0.;
+        volneg[3] = 0.;
+      } else if (pb == dummypoint) {
+        volneg[0] = 0.;
+        volneg[1] = 0.;
+        volneg[2] = tetprismvol(pp, pd, pc, pa);
+        volneg[3] = 0.;
+      } else if (pc == dummypoint) {
+        volneg[0] = tetprismvol(pp, pd, pa, pb);
+        volneg[1] = 0.;
+        volneg[2] = 0.;
+        volneg[3] = 0.;
+      } else { // pd == dummypoint
+        volneg[0] = 0.;
+        volneg[1] = 0.;
+        volneg[2] = 0.;
+        volneg[3] = tetprismvol(pa, pb, pc, pp);
+      }
+      volpos[0] = 0.;
+    } else if (dummyflag < 0) {
+      volneg[0] = 0.;
+      volneg[1] = 0.;
+      volneg[2] = 0.;
+      volneg[3] = 0.;
+      volpos[0] = tetprismvol(pa, pb, pc, pd);
+    } else {
+      volneg[0] = tetprismvol(pp, pd, pa, pb);
+      volneg[1] = tetprismvol(pp, pd, pb, pc);
+      volneg[2] = tetprismvol(pp, pd, pc, pa);
+      volneg[3] = tetprismvol(pa, pb, pc, pp);
+      volpos[0] = tetprismvol(pa, pb, pc, pd);
+    }
+    vol_diff = volpos[0] - volneg[0] - volneg[1] - volneg[2] - volneg[3];
+    fc->tetprism_vol_sum  += vol_diff; // Update the total sum.
+  }
+
+  // Bond the new tet to adjacent tets.
+  for (i = 0; i < 3; i++) {
+    esym(fliptets[0], newface); // At faces [b,a,d], [c,b,d], [a,c,d].
+    bond(newface, topcastets[i]);
+    enextself(fliptets[0]);
+  }
+  bond(fliptets[0], botcastet);
+
+  if (checksubsegflag) {
+    face checkseg;
+    // Bond 6 segments (at edges of [a,b,c,d]) if there there are.
+    for (i = 0; i < 3; i++) {
+      eprev(topcastets[i], newface); // At edges [d,a],[d,b],[d,c].
+      if (issubseg(newface)) {
+        tsspivot1(newface, checkseg);
+        esym(fliptets[0], newface);
+        enextself(newface); // At edges [a,d], [b,d], [c,d].
+        tssbond1(newface, checkseg);
+        sstbond1(checkseg, newface);
+        if (fc->chkencflag & 1) {
+          enqueuesubface(badsubsegs, &checkseg);
+        }
+      }
+      enextself(fliptets[0]);
+    }
+    for (i = 0; i < 3; i++) {
+      if (issubseg(topcastets[i])) {
+        tsspivot1(topcastets[i], checkseg); // At edges [a,b],[b,c],[c,a].
+        tssbond1(fliptets[0], checkseg);
+        sstbond1(checkseg, fliptets[0]);
+        if (fc->chkencflag & 1) {
+          enqueuesubface(badsubsegs, &checkseg);
+        }
+      }
+      enextself(fliptets[0]);
+    }
+  }
+
+  if (checksubfaceflag) {
+    face checksh;
+    // Bond 4 subfaces (at faces of [a,b,c,d]) if there are.
+    for (i = 0; i < 3; i++) {
+      if (issubface(topcastets[i])) {
+        tspivot(topcastets[i], checksh); // At faces [a,b,d],[b,c,d],[c,a,d]
+        esym(fliptets[0], newface); // At faces [b,a,d],[c,b,d],[a,c,d]
+        sesymself(checksh);
+        tsbond(newface, checksh);
+        if (fc->chkencflag & 2) {
+          enqueuesubface(badsubfacs, &checksh);
+        }
+      }
+      enextself(fliptets[0]);
+    }
+    if (issubface(botcastet)) {
+      tspivot(botcastet, checksh); // At face [b,a,c]
+      sesymself(checksh);
+      tsbond(fliptets[0], checksh);
+      if (fc->chkencflag & 2) {
+        enqueuesubface(badsubfacs, &checksh);
+      }
+    }
+
+    if (spivot >= 0) {
+      // Perform a 3-to-1 flip in surface triangulation.
+      // Depending on the value of 'spivot', the three subfaces are:
+      //   - 0: [a,b,p], [b,d,p], [d,a,p]
+      //   - 1: [b,c,p], [c,d,p], [d,b,p] 
+      //   - 2: [c,a,p], [a,d,p], [d,c,p] 
+      //   - 3: [a,b,p], [b,c,p], [c,a,p]
+      // Adjust the three subfaces such that their origins are p, i.e., 
+      //   - 3: [p,a,b], [p,b,c], [p,c,a]. (Required by the flip31()).
+      for (i = 0; i < 3; i++) {
+        senext2self(flipshs[i]);
+      }
+      flip31(flipshs, 0);
+      // Delete the three old subfaces.
+      for (i = 0; i < 3; i++) {
+        shellfacedealloc(subfaces, flipshs[i].sh);
+      }
+      if (spivot < 3) {
+        // // Bond the new subface to the new tet [a,b,c,d].
+        tsbond(topcastets[spivot], flipshs[3]);
+        fsym(topcastets[spivot], newface);
+        sesym(flipshs[3], checksh);
+        tsbond(newface, checksh);
+      } else {
+        // Bound the new subface [a,b,c] to the new tet [a,b,c,d].
+        tsbond(fliptets[0], flipshs[3]);
+        fsym(fliptets[0], newface);
+        sesym(flipshs[3], checksh);
+        tsbond(newface, checksh);
+      }
+    } // if (spivot > 0)
+  } // if (checksubfaceflag)
+
+  if (fc->chkencflag & 4) {
+    enqueuetetrahedron(&(fliptets[0]));
+  }
+
+  // Update the point-to-tet map.
+  setpoint2tet(pa, (tetrahedron) fliptets[0].tet);
+  setpoint2tet(pb, (tetrahedron) fliptets[0].tet);
+  setpoint2tet(pc, (tetrahedron) fliptets[0].tet);
+  setpoint2tet(pd, (tetrahedron) fliptets[0].tet);
+
+  if (fc->enqflag > 0) {
+    // Queue faces which may be locally non-Delaunay.
+    flippush(flipstack, &(fliptets[0])); // [a,b,c] (opposite to new point).
+    if (fc->enqflag > 1) {
+      for (i = 0; i < 3; i++) {
+        esym(fliptets[0], newface);
+        flippush(flipstack, &newface);
+        enextself(fliptets[0]);
+      }
+    }
+  }
+
+  recenttet = fliptets[0];
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// flipnm()    Flip an edge through a sequence of elementary flips.          //
+//                                                                           //
+// 'abtets' is an array of 'n' tets in the star of edge [a,b].These tets are //
+// ordered in a counterclockwise cycle with respect to the vector a->b, i.e.,//
+// use the right-hand rule.                                                  //
+//                                                                           //
+// 'level' (>= 0) indicates the current link level. If 'level > 0', we are   //
+// flipping a link edge of an edge [a',b'],  and 'abedgepivot' indicates     //
+// which link edge, i.e., [c',b'] or [a',c'], is [a,b]  These two parameters //
+// allow us to determine the new tets after a 3-to-2 flip, i.e., tets that   //
+// do not inside the reduced star of edge [a',b'].                           //
+//                                                                           //
+// If the flag 'fc->unflip' is set, this routine un-does the flips performed //
+// in flipnm([a,b]) so that the mesh is returned to its original state       //
+// before doing the flipnm([a,b]) operation.                                 //
+//                                                                           //
+// The return value is an integer nn, where nn <= n.  If nn is 2, then the   //
+// edge is flipped.  The first and the second tets in 'abtets' are new tets. //
+// Otherwise, nn > 2, the edge is not flipped, and nn is the number of tets  //
+// in the current star of [a,b].                                             //
+//                                                                           //
+// ASSUMPTIONS:                                                              //
+//  - Neither a nor b is 'dummypoint'.                                       //
+//  - [a,b] must not be a segment.                                           //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::flipnm(triface* abtets, int n, int level, int abedgepivot,
+                       flipconstraints* fc)
+{
+  triface fliptets[3], spintet, flipedge;
+  triface *tmpabtets, *parytet;
+  point pa, pb, pc, pd, pe, pf;
+  REAL ori;
+  int hullflag, hulledgeflag;
+  int reducflag, rejflag;
+  int reflexlinkedgecount;
+  int edgepivot;
+  int n1, nn;
+  int t1ver;
+  int i, j;
+
+  pa = org(abtets[0]);
+  pb = dest(abtets[0]);
+
+  if (n > 3) {
+    // Try to reduce the size of the Star(ab) by flipping a face in it. 
+    reflexlinkedgecount = 0;
+
+    for (i = 0; i < n; i++) {
+      // Let the face of 'abtets[i]' be [a,b,c].
+      if (checksubfaceflag) {
+        if (issubface(abtets[i])) {
+          continue; // Skip a subface.
+        }
+      }
+      // Do not flip this face if it is involved in two Stars.
+      if ((elemcounter(abtets[i]) > 1) ||
+          (elemcounter(abtets[(i - 1 + n) % n]) > 1)) {
+        continue;
+      }
+
+      pc = apex(abtets[i]); 
+      pd = apex(abtets[(i + 1) % n]);
+      pe = apex(abtets[(i - 1 + n) % n]);
+      if ((pd == dummypoint) || (pe == dummypoint)) {
+        continue; // [a,b,c] is a hull face.
+      }
+
+
+      // Decide whether [a,b,c] is flippable or not.
+      reducflag = 0; 
+
+      hullflag = (pc == dummypoint); // pc may be dummypoint.
+      hulledgeflag = 0;
+      if (hullflag == 0) {
+        ori = orient3d(pb, pc, pd, pe); // Is [b,c] locally convex?
+        if (ori > 0) {
+          ori = orient3d(pc, pa, pd, pe); // Is [c,a] locally convex?
+          if (ori > 0) {
+            // Test if [a,b] is locally convex OR flat.
+            ori = orient3d(pa, pb, pd, pe);
+            if (ori > 0) {
+              // Found a 2-to-3 flip: [a,b,c] => [e,d]
+              reducflag = 1;
+            } else if (ori == 0) {
+              // [a,b] is flat.
+              if (n == 4) {
+                // The "flat" tet can be removed immediately by a 3-to-2 flip.
+                reducflag = 1;
+                // Check if [e,d] is a hull edge.
+                pf = apex(abtets[(i + 2) % n]);
+                hulledgeflag = (pf == dummypoint);
+              }
+            }
+          }
+        }
+        if (!reducflag) {
+          reflexlinkedgecount++;
+        }
+      } else {
+        // 'c' is dummypoint.
+        if (n == 4) {
+          // Let the vertex opposite to 'c' is 'f'.
+          // A 4-to-4 flip is possible if the two tets [d,e,f,a] and [e,d,f,b]
+          //   are valid tets. 
+          // Note: When the mesh is not convex, it is possible that [a,b] is
+          //   locally non-convex (at hull faces [a,b,e] and [b,a,d]).
+          //   In this case, an edge flip [a,b] to [e,d] is still possible.
+          pf = apex(abtets[(i + 2) % n]);
+          ori = orient3d(pd, pe, pf, pa);
+          if (ori < 0) {
+            ori = orient3d(pe, pd, pf, pb);
+            if (ori < 0) {
+              // Found a 4-to-4 flip: [a,b] => [e,d]
+              reducflag = 1;
+              ori = 0; // Signal as a 4-to-4 flip (like a co-planar case).
+              hulledgeflag = 1; // [e,d] is a hull edge.
+            }
+          }
+        }
+      } // if (hullflag)
+
+      if (reducflag) {
+        if (nonconvex && hulledgeflag) {
+          // We will create a hull edge [e,d]. Make sure it does not exist.
+          if (getedge(pe, pd, &spintet)) {
+            // The 2-to-3 flip is not a topological valid flip. 
+            reducflag = 0;
+          }
+        }
+      }
+
+      if (reducflag) {
+        // [a,b,c] could be removed by a 2-to-3 flip.
+        rejflag = 0;
+        if (fc->checkflipeligibility) {
+          // Check if the flip can be performed.
+          rejflag = checkflipeligibility(1, pa, pb, pc, pd, pe, level,
+                                         abedgepivot, fc);
+        }
+        if (!rejflag) {
+          // Do flip: [a,b,c] => [e,d].
+          fliptets[0] = abtets[i];
+          fsym(fliptets[0], fliptets[1]); // abtets[i-1].
+          flip23(fliptets, hullflag, fc);
+
+          // Shrink the array 'abtets', maintain the original order.
+          //   Two tets 'abtets[i-1] ([a,b,e,c])' and 'abtets[i] ([a,b,c,d])'
+          //   are flipped, i.e., they do not in Star(ab) anymore. 
+          //   'fliptets[0]' ([e,d,a,b]) is in Star(ab), it is saved in
+          //   'abtets[i-1]' (adjust it to be [a,b,e,d]), see below: 
+          // 
+          //            before                   after
+          //     [0] |___________|        [0] |___________| 
+          //     ... |___________|        ... |___________|
+          //   [i-1] |_[a,b,e,c]_|      [i-1] |_[a,b,e,d]_|
+          //     [i] |_[a,b,c,d]_| -->    [i] |_[a,b,d,#]_|
+          //   [i+1] |_[a,b,d,#]_|      [i+1] |_[a,b,#,*]_|
+          //     ... |___________|        ... |___________|
+          //   [n-2] |___________|      [n-2] |___________| 
+          //   [n-1] |___________|      [n-1] |_[i]_2-t-3_|
+          //
+          edestoppoself(fliptets[0]); // [a,b,e,d]
+          // Increase the counter of this new tet (it is in Star(ab)).
+          increaseelemcounter(fliptets[0]); 
+          abtets[(i - 1 + n) % n] = fliptets[0];
+          for (j = i; j < n - 1; j++) {
+            abtets[j] = abtets[j + 1];  // Upshift
+          }
+          // The last entry 'abtets[n-1]' is empty. It is used in two ways:
+          //   (i) it remembers the vertex 'c' (in 'abtets[n-1].tet'), and
+          //  (ii) it remembers the position [i] where this flip took place.
+          // These information let us to either undo this flip or recover
+          //   the original edge link (for collecting new created tets).
+          abtets[n - 1].tet = (tetrahedron *) pc;
+          abtets[n - 1].ver = 0; // Clear it.
+          // 'abtets[n - 1].ver' is in range [0,11] -- only uses 4 bits.
+          // Use the 5th bit in 'abtets[n - 1].ver' to signal a 2-to-3 flip.
+          abtets[n - 1].ver |= (1 << 4);
+          // The poisition [i] of this flip is saved above the 7th bit.
+          abtets[n - 1].ver |= (i << 6);
+
+          if (fc->collectnewtets) {
+            // Push the two new tets [e,d,b,c] and [e,d,c,a] into a stack.
+            //   Re-use the global array 'cavetetlist'.
+            for (j = 1; j < 3; j++) {
+              cavetetlist->newindex((void **) &parytet);
+              *parytet = fliptets[j]; // fliptets[1], fliptets[2].
+            }
+          }
+
+          // Star(ab) is reduced. Try to flip the edge [a,b].
+          nn = flipnm(abtets, n - 1, level, abedgepivot, fc);
+
+          if (nn == 2) {
+            // The edge has been flipped.
+            return nn;
+          } else { // if (nn > 2)
+            // The edge is not flipped.
+            if (fc->unflip || (ori == 0)) {
+              // Undo the previous 2-to-3 flip, i.e., do a 3-to-2 flip to 
+              //   transform [e,d] => [a,b,c].
+              // 'ori == 0' means that the previous flip created a degenerated
+              //   tet. It must be removed. 
+              // Remember that 'abtets[i-1]' is [a,b,e,d]. We can use it to
+              //   find another two tets [e,d,b,c] and [e,d,c,a].
+              fliptets[0] = abtets[(i-1 + (n-1)) % (n-1)]; // [a,b,e,d]
+              edestoppoself(fliptets[0]); // [e,d,a,b]
+              fnext(fliptets[0], fliptets[1]); // [1] is [e,d,b,c]
+              fnext(fliptets[1], fliptets[2]); // [2] is [e,d,c,a]
+              // Restore the two original tets in Star(ab). 
+              flip32(fliptets, hullflag, fc);
+              // Marktest the two restored tets in Star(ab).
+              for (j = 0; j < 2; j++) {
+                increaseelemcounter(fliptets[j]);
+              }
+              // Expand the array 'abtets', maintain the original order.
+              for (j = n - 2; j>= i; j--) {
+                abtets[j + 1] = abtets[j];  // Downshift
+              }
+              // Insert the two new tets 'fliptets[0]' [a,b,c,d] and 
+              //  'fliptets[1]' [b,a,c,e] into the (i-1)-th and i-th entries, 
+              //  respectively.
+              esym(fliptets[1], abtets[(i - 1 + n) % n]); // [a,b,e,c]
+              abtets[i] = fliptets[0]; // [a,b,c,d]
+              nn++;
+              if (fc->collectnewtets) {
+                // Pop two (flipped) tets from the stack.
+                cavetetlist->objects -= 2;
+              }
+            } // if (unflip || (ori == 0))
+          } // if (nn > 2)
+
+          if (!fc->unflip) {
+            // The flips are not reversed. The current Star(ab) can not be
+            //   further reduced. Return its current size (# of tets).
+            return nn; 
+          }
+          // unflip is set. 
+          // Continue the search for flips.
+        }
+      } // if (reducflag)
+    } // i
+
+    // The Star(ab) is not reduced. 
+    if (reflexlinkedgecount > 0) {
+      // There are reflex edges in the Link(ab).
+      if (((b->fliplinklevel < 0) && (level < autofliplinklevel)) || 
+          ((b->fliplinklevel >= 0) && (level < b->fliplinklevel))) {
+        // Try to reduce the Star(ab) by flipping a reflex edge in Link(ab).
+        for (i = 0; i < n; i++) {
+          // Do not flip this face [a,b,c] if there are two Stars involved.
+          if ((elemcounter(abtets[i]) > 1) ||
+              (elemcounter(abtets[(i - 1 + n) % n]) > 1)) {
+            continue;
+          }
+          pc = apex(abtets[i]);
+          if (pc == dummypoint) {
+            continue; // [a,b] is a hull edge.
+          }
+          pd = apex(abtets[(i + 1) % n]);
+          pe = apex(abtets[(i - 1 + n) % n]);
+          if ((pd == dummypoint) || (pe == dummypoint)) {
+            continue; // [a,b,c] is a hull face.
+          }
+
+
+          edgepivot = 0; // No edge is selected yet.
+
+          // Test if [b,c] is locally convex or flat.
+          ori = orient3d(pb, pc, pd, pe);
+          if (ori <= 0) {
+            // Select the edge [c,b].
+            enext(abtets[i], flipedge); // [b,c,a,d]
+            edgepivot = 1;
+          }
+          if (!edgepivot) {
+            // Test if [c,a] is locally convex or flat.
+            ori = orient3d(pc, pa, pd, pe);
+            if (ori <= 0) {
+              // Select the edge [a,c].
+              eprev(abtets[i], flipedge); // [c,a,b,d].
+              edgepivot = 2;
+            }
+          }
+
+          if (!edgepivot) continue;
+
+          // An edge is selected.
+          if (checksubsegflag) {
+            // Do not flip it if it is a segment.
+            if (issubseg(flipedge)) {
+              if (fc->collectencsegflag) {
+                face checkseg, *paryseg;
+                tsspivot1(flipedge, checkseg);
+                if (!sinfected(checkseg)) {
+                  // Queue this segment in list.
+                  sinfect(checkseg);                
+                  caveencseglist->newindex((void **) &paryseg);
+                  *paryseg = checkseg;
+                }
+              }
+              continue;
+            }
+          }
+
+          // Try to flip the selected edge ([c,b] or [a,c]).
+          esymself(flipedge); 
+          // Count the number of tets at the edge.
+          n1 = 0;
+          j = 0; // Sum of the star counters.
+          spintet = flipedge;
+          while (1) {
+            n1++;
+            j += (elemcounter(spintet)); 
+            fnextself(spintet);
+            if (spintet.tet == flipedge.tet) break;
+          }
+          if (n1 < 3) {
+            // This is only possible when the mesh contains inverted
+            //   elements.  Reprot a bug.
+            terminatetetgen(this, 2);
+          }
+          if (j > 2) {
+            // The Star(flipedge) overlaps other Stars.
+            continue; // Do not flip this edge.
+          }
+
+          if ((b->flipstarsize > 0) && (n1 > b->flipstarsize)) {
+            // The star size exceeds the given limit.
+            continue; // Do not flip it.
+          }
+
+          // Allocate spaces for Star(flipedge).
+          tmpabtets = new triface[n1];
+          // Form the Star(flipedge).
+          j = 0;
+          spintet = flipedge;
+          while (1) {
+            tmpabtets[j] = spintet;
+            // Increase the star counter of this tet.
+            increaseelemcounter(tmpabtets[j]); 
+            j++;
+            fnextself(spintet);
+            if (spintet.tet == flipedge.tet) break;
+          }
+
+          // Try to flip the selected edge away.
+          nn = flipnm(tmpabtets, n1, level + 1, edgepivot, fc);
+
+          if (nn == 2) {
+            // The edge is flipped. Star(ab) is reduced.
+            // Shrink the array 'abtets', maintain the original order.
+            if (edgepivot == 1) {
+              // 'tmpabtets[0]' is [d,a,e,b] => contains [a,b].
+              spintet = tmpabtets[0]; // [d,a,e,b]
+              enextself(spintet);
+              esymself(spintet);
+              enextself(spintet); // [a,b,e,d]
+            } else {
+              // 'tmpabtets[1]' is [b,d,e,a] => contains [a,b].
+              spintet = tmpabtets[1]; // [b,d,e,a]
+              eprevself(spintet);
+              esymself(spintet);
+              eprevself(spintet); // [a,b,e,d]
+            } // edgepivot == 2
+            increaseelemcounter(spintet); // It is in Star(ab).
+            // Put the new tet at [i-1]-th entry.
+            abtets[(i - 1 + n) % n] = spintet;
+            for (j = i; j < n - 1; j++) {
+              abtets[j] = abtets[j + 1];  // Upshift
+            }
+            // Remember the flips in the last entry of the array 'abtets'.
+            // They can be used to recover the flipped edge.
+            abtets[n - 1].tet = (tetrahedron *) tmpabtets; // The star(fedge).
+            abtets[n - 1].ver = 0; // Clear it.
+            // Use the 1st and 2nd bit to save 'edgepivot' (1 or 2).
+            abtets[n - 1].ver |= edgepivot;
+            // Use the 6th bit to signal this n1-to-m1 flip.
+            abtets[n - 1].ver |= (1 << 5); 
+            // The poisition [i] of this flip is saved from 7th to 19th bit.
+            abtets[n - 1].ver |= (i << 6);
+            // The size of the star 'n1' is saved from 20th bit.
+            abtets[n - 1].ver |= (n1 << 19);
+
+            // Remember the flipped link vertex 'c'. It can be used to recover
+            //   the original edge link of [a,b], and to collect new tets.
+            tmpabtets[0].tet = (tetrahedron *) pc;
+            tmpabtets[0].ver = (1 << 5); // Flag it as a vertex handle.
+
+            // Continue to flip the edge [a,b].
+            nn = flipnm(abtets, n - 1, level, abedgepivot, fc);
+
+            if (nn == 2) { 
+              // The edge has been flipped.
+              return nn;
+            } else { // if (nn > 2) {
+              // The edge is not flipped.
+              if (fc->unflip) {
+                // Recover the flipped edge ([c,b] or [a,c]).
+                // The sequence of flips are saved in 'tmpabtets'. 
+                // abtets[(i-1) % (n-1)] is [a,b,e,d], i.e., the tet created by
+                //   the flipping of edge [c,b] or [a,c].It must still exist in
+                //   Star(ab). It is the start tet to recover the flipped edge.
+                if (edgepivot == 1) { 
+                  // The flip edge is [c,b].
+                  tmpabtets[0] = abtets[((i-1)+(n-1))%(n-1)]; // [a,b,e,d]
+                  eprevself(tmpabtets[0]);
+                  esymself(tmpabtets[0]);
+                  eprevself(tmpabtets[0]); // [d,a,e,b]
+                  fsym(tmpabtets[0], tmpabtets[1]); // [a,d,e,c]
+                } else {
+                  // The flip edge is [a,c].
+                  tmpabtets[1] = abtets[((i-1)+(n-1))%(n-1)]; // [a,b,e,d]
+                  enextself(tmpabtets[1]);
+                  esymself(tmpabtets[1]);
+                  enextself(tmpabtets[1]); // [b,d,e,a]
+                  fsym(tmpabtets[1], tmpabtets[0]); // [d,b,e,c]
+                } // if (edgepivot == 2)
+
+                // Recover the flipped edge ([c,b] or [a,c]).
+                flipnm_post(tmpabtets, n1, 2, edgepivot, fc);
+
+                // Insert the two recovered tets into Star(ab).
+                for (j = n - 2; j >= i; j--) {
+                  abtets[j + 1] = abtets[j];  // Downshift
+                }
+                if (edgepivot == 1) {
+                  // tmpabtets[0] is [c,b,d,a] ==> contains [a,b]
+                  // tmpabtets[1] is [c,b,a,e] ==> contains [a,b]
+                  // tmpabtets[2] is [c,b,e,d]
+                  fliptets[0] = tmpabtets[1];
+                  enextself(fliptets[0]);
+                  esymself(fliptets[0]); // [a,b,e,c]
+                  fliptets[1] = tmpabtets[0];
+                  esymself(fliptets[1]);
+                  eprevself(fliptets[1]); // [a,b,c,d]
+                } else {
+                  // tmpabtets[0] is [a,c,d,b] ==> contains [a,b]
+                  // tmpabtets[1] is [a,c,b,e] ==> contains [a,b]
+                  // tmpabtets[2] is [a,c,e,d]
+                  fliptets[0] = tmpabtets[1];
+                  eprevself(fliptets[0]);
+                  esymself(fliptets[0]); // [a,b,e,c]
+                  fliptets[1] = tmpabtets[0];
+                  esymself(fliptets[1]);
+                  enextself(fliptets[1]); // [a,b,c,d]
+                } // edgepivot == 2
+                for (j = 0; j < 2; j++) {
+                  increaseelemcounter(fliptets[j]);
+                }
+                // Insert the two recovered tets into Star(ab).
+                abtets[(i - 1 + n) % n] = fliptets[0];
+                abtets[i] = fliptets[1];
+                nn++;
+                // Release the allocated spaces.
+                delete [] tmpabtets;
+              } // if (unflip)
+            } // if (nn > 2)
+
+            if (!fc->unflip) {
+              // The flips are not reversed. The current Star(ab) can not be
+              //   further reduced. Return its size (# of tets).
+              return nn; 
+            }
+            // unflip is set. 
+            // Continue the search for flips.
+          } else {
+            // The selected edge is not flipped.
+            if (!fc->unflip) {
+              // Release the memory used in this attempted flip.
+              flipnm_post(tmpabtets, n1, nn, edgepivot, fc);
+            }
+            // Decrease the star counters of tets in Star(flipedge).
+            for (j = 0; j < nn; j++) {
+              decreaseelemcounter(tmpabtets[j]);
+            }
+            // Release the allocated spaces.
+            delete [] tmpabtets;
+          }
+        } // i
+      } // if (level...)
+    } // if (reflexlinkedgecount > 0)
+  } else {
+    // Check if a 3-to-2 flip is possible.
+    // Let the three apexes be c, d,and e. Hull tets may be involved. If so, 
+    //   we rearrange them such that the vertex e is dummypoint. 
+    hullflag = 0;
+
+    if (apex(abtets[0]) == dummypoint) {
+      pc = apex(abtets[1]);
+      pd = apex(abtets[2]);
+      pe = apex(abtets[0]);
+      hullflag = 1;
+    } else if (apex(abtets[1]) == dummypoint) {
+      pc = apex(abtets[2]);
+      pd = apex(abtets[0]);
+      pe = apex(abtets[1]);
+      hullflag = 2;
+    } else {
+      pc = apex(abtets[0]);
+      pd = apex(abtets[1]);
+      pe = apex(abtets[2]);
+      hullflag = (pe == dummypoint) ? 3 : 0;
+    }
+
+    reducflag = 0;
+    rejflag = 0;
+
+
+    if (hullflag == 0) {
+      // Make sure that no inverted tet will be created, i.e. the new tets
+      //   [d,c,e,a] and [c,d,e,b] must be valid tets. 
+      ori = orient3d(pd, pc, pe, pa);
+      if (ori < 0) {
+        ori = orient3d(pc, pd, pe, pb);
+        if (ori < 0) {
+          reducflag = 1;
+        }
+      }
+    } else {
+      // [a,b] is a hull edge.
+      //   Note: This can happen when it is in the middle of a 4-to-4 flip.
+      //   Note: [a,b] may even be a non-convex hull edge.
+      if (!nonconvex) {
+        //  The mesh is convex, only do flip if it is a coplanar hull edge.
+        ori = orient3d(pa, pb, pc, pd); 
+        if (ori == 0) {
+          reducflag = 1;
+        }
+      } else { // nonconvex
+        reducflag = 1;
+      }
+      if (reducflag == 1) {
+        // [a,b], [a,b,c] and [a,b,d] are on the convex hull.
+        // Make sure that no inverted tet will be created.
+        point searchpt = NULL, chkpt;
+        REAL bigvol = 0.0, ori1, ori2;
+        // Search an interior vertex which is an apex of edge [c,d].
+        //   In principle, it can be arbitrary interior vertex.  To avoid
+        //   numerical issue, we choose the vertex which belongs to a tet
+        //   't' at edge [c,d] and 't' has the biggest volume.  
+        fliptets[0] = abtets[hullflag % 3]; // [a,b,c,d].
+        eorgoppoself(fliptets[0]);  // [d,c,b,a]
+        spintet = fliptets[0];
+        while (1) {
+          fnextself(spintet);
+          chkpt = oppo(spintet);
+          if (chkpt == pb) break;
+          if ((chkpt != dummypoint) && (apex(spintet) != dummypoint)) {
+            ori = -orient3d(pd, pc, apex(spintet), chkpt);
+            if (ori > bigvol) {
+              bigvol = ori;
+              searchpt = chkpt;
+            }
+          }
+        }
+        if (searchpt != NULL) { 
+          // Now valid the configuration.
+          ori1 = orient3d(pd, pc, searchpt, pa);
+          ori2 = orient3d(pd, pc, searchpt, pb);
+          if (ori1 * ori2 >= 0.0) {
+            reducflag = 0; // Not valid. 
+          } else {
+            ori1 = orient3d(pa, pb, searchpt, pc);
+            ori2 = orient3d(pa, pb, searchpt, pd);
+            if (ori1 * ori2 >= 0.0) {
+              reducflag = 0; // Not valid.
+            }
+          }
+        } else {
+          // No valid searchpt is found.
+          reducflag = 0; // Do not flip it.
+        }
+      } // if (reducflag == 1)
+    } // if (hullflag == 1)
+
+    if (reducflag) {
+      // A 3-to-2 flip is possible.
+      if (checksubfaceflag) {
+        // This edge (must not be a segment) can be flipped ONLY IF it belongs
+        //   to either 0 or 2 subfaces.  In the latter case, a 2-to-2 flip in 
+        //   the surface mesh will be automatically performed within the 
+        //   3-to-2 flip.
+        nn = 0;
+        edgepivot = -1; // Re-use it.
+        for (j = 0; j < 3; j++) {
+          if (issubface(abtets[j])) {
+            nn++; // Found a subface.
+          } else {
+            edgepivot = j;
+          }
+        }
+        if (nn == 1) {
+          // Found only 1 subface containing this edge. This can happen in 
+          //   the boundary recovery phase. The neighbor subface is not yet 
+          //   recovered. This edge should not be flipped at this moment.
+          rejflag = 1; 
+        } else if (nn == 2) {
+          // Found two subfaces. A 2-to-2 flip is possible. Validate it.
+          // Below we check if the two faces [p,q,a] and [p,q,b] are subfaces.
+          eorgoppo(abtets[(edgepivot + 1) % 3], spintet); // [q,p,b,a]
+          if (issubface(spintet)) {
+            rejflag = 1; // Conflict to a 2-to-2 flip.
+          } else {
+            esymself(spintet);
+            if (issubface(spintet)) {
+              rejflag = 1; // Conflict to a 2-to-2 flip.
+            }
+          }
+        } else if (nn == 3) {
+          // Report a bug.
+          terminatetetgen(this, 2);
+        }
+      }
+      if (!rejflag && fc->checkflipeligibility) {
+        // Here we must exchange 'a' and 'b'. Since in the check... function,
+        //   we assume the following point sequence, 'a,b,c,d,e', where
+        //   the face [a,b,c] will be flipped and the edge [e,d] will be
+        //   created. The two new tets are [a,b,c,d] and [b,a,c,e]. 
+        rejflag = checkflipeligibility(2, pc, pd, pe, pb, pa, level, 
+                                       abedgepivot, fc);
+      }
+      if (!rejflag) {
+        // Do flip: [a,b] => [c,d,e]
+        flip32(abtets, hullflag, fc);
+        if (fc->remove_ndelaunay_edge) {
+          if (level == 0) {
+            // It is the desired removing edge. Check if we have improved
+            //   the objective function.
+            if ((fc->tetprism_vol_sum >= 0.0) ||
+                (fabs(fc->tetprism_vol_sum) < fc->bak_tetprism_vol)) {
+              // No improvement! flip back: [c,d,e] => [a,b].
+              flip23(abtets, hullflag, fc);
+              // Increase the element counter -- They are in cavity.
+              for (j = 0; j < 3; j++) {
+                increaseelemcounter(abtets[j]); 
+              }
+              return 3;
+            }
+          } // if (level == 0)
+        }
+        if (fc->collectnewtets) {
+          // Collect new tets.
+          if (level == 0) {
+            // Push the two new tets into stack.
+            for (j = 0; j < 2; j++) {
+              cavetetlist->newindex((void **) &parytet);
+              *parytet = abtets[j];
+            }
+          } else {
+            // Only one of the new tets is collected. The other one is inside
+            //   the reduced edge star. 'abedgepivot' is either '1' or '2'.
+            cavetetlist->newindex((void **) &parytet);
+            if (abedgepivot == 1) { // [c,b]
+              *parytet = abtets[1];
+            } else {
+              *parytet = abtets[0];
+            }
+          }
+        } // if (fc->collectnewtets)
+        return 2;
+      }
+    } // if (reducflag)
+  } // if (n == 3)
+
+  // The current (reduced) Star size.
+  return n;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// flipnm_post()    Post process a n-to-m flip.                              //
+//                                                                           //
+// IMPORTANT: This routine only works when there is no other flip operation  //
+// is done after flipnm([a,b]) which attempts to remove an edge [a,b].       //
+//                                                                           //
+// 'abtets' is an array of 'n' (>= 3) tets which are in the original star of //
+// [a,b] before flipnm([a,b]).  'nn' (< n) is the value returned by flipnm.  //
+// If 'nn == 2', the edge [a,b] has been flipped. 'abtets[0]' and 'abtets[1]'//
+// are [c,d,e,b] and [d,c,e,a], i.e., a 2-to-3 flip can recover the edge [a, //
+// b] and its initial Star([a,b]).  If 'nn >= 3' edge [a,b] still exists in  //
+// current mesh and 'nn' is the current number of tets in Star([a,b]).       //
+//                                                                           //
+// Each 'abtets[i]', where nn <= i < n, saves either a 2-to-3 flip or a      //
+// flipnm([p1,p2]) operation ([p1,p2] != [a,b]) which created the tet        //
+// 'abtets[t-1]', where '0 <= t <= i'.  These information can be used to     //
+// undo the flips performed in flipnm([a,b]) or to collect new tets created  //
+// by the flipnm([a,b]) operation.                                           //
+//                                                                           //
+// Default, this routine only walks through the flips and frees the spaces   //
+// allocated during the flipnm([a,b]) operation.                             //
+//                                                                           //
+// If the flag 'fc->unflip' is set, this routine un-does the flips performed //
+// in flipnm([a,b]) so that the mesh is returned to its original state       //
+// before doing the flipnm([a,b]) operation.                                 //
+//                                                                           //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::flipnm_post(triface* abtets, int n, int nn, int abedgepivot,
+                            flipconstraints* fc)
+{
+  triface fliptets[3], flipface;
+  triface *tmpabtets;
+  int fliptype;
+  int edgepivot;
+  int t, n1;
+  int i, j;
+
+
+  if (nn == 2) {
+    // The edge [a,b] has been flipped.
+    // 'abtets[0]' is [c,d,e,b] or [#,#,#,b].
+    // 'abtets[1]' is [d,c,e,a] or [#,#,#,a].
+    if (fc->unflip) {
+      // Do a 2-to-3 flip to recover the edge [a,b]. There may be hull tets.
+      flip23(abtets, 1, fc);
+      if (fc->collectnewtets) {
+        // Pop up new (flipped) tets from the stack.
+        if (abedgepivot == 0) {
+          // Two new tets were collected.
+          cavetetlist->objects -= 2;
+        } else {
+          // Only one of the two new tets was collected.
+          cavetetlist->objects -= 1;
+        }
+      }
+    } 
+    // The initial size of Star(ab) is 3.
+    nn++;
+  } 
+
+  // Walk through the performed flips.
+  for (i = nn; i < n; i++) {
+    // At the beginning of each step 'i', the size of the Star([a,b]) is 'i'.
+    // At the end of this step, the size of the Star([a,b]) is 'i+1'.
+    // The sizes of the Link([a,b]) are the same.
+    fliptype = ((abtets[i].ver >> 4) & 3); // 0, 1, or 2.
+    if (fliptype == 1) {
+      // It was a 2-to-3 flip: [a,b,c]->[e,d].
+      t = (abtets[i].ver >> 6);
+      if (fc->unflip) {
+        if (b->verbose > 2) {
+          printf("      Recover a 2-to-3 flip at f[%d].\n", t);
+        }
+        // 'abtets[(t-1)%i]' is the tet [a,b,e,d] in current Star(ab), i.e.,
+        //   it is created by a 2-to-3 flip [a,b,c] => [e,d].
+        fliptets[0] = abtets[((t - 1) + i) % i]; // [a,b,e,d]
+        eprevself(fliptets[0]);
+        esymself(fliptets[0]);
+        enextself(fliptets[0]); // [e,d,a,b]
+        fnext(fliptets[0], fliptets[1]); // [e,d,b,c]
+        fnext(fliptets[1], fliptets[2]); // [e,d,c,a]
+        // Do a 3-to-2 flip: [e,d] => [a,b,c].
+        // NOTE: hull tets may be invloved.
+        flip32(fliptets, 1, fc);
+        // Expand the array 'abtets', maintain the original order.
+        // The new array length is (i+1).
+        for (j = i - 1; j >= t; j--) {
+          abtets[j + 1] = abtets[j];  // Downshift
+        }
+        // The tet abtets[(t-1)%i] is deleted. Insert the two new tets 
+        //   'fliptets[0]' [a,b,c,d] and 'fliptets[1]' [b,a,c,e] into
+        //   the (t-1)-th and t-th entries, respectively.
+        esym(fliptets[1], abtets[((t-1) + (i+1)) % (i+1)]); // [a,b,e,c]
+        abtets[t] = fliptets[0]; // [a,b,c,d]
+        if (fc->collectnewtets) {
+          // Pop up two (flipped) tets from the stack.
+          cavetetlist->objects -= 2;
+        }
+      } 
+    } else if (fliptype == 2) {
+      tmpabtets = (triface *) (abtets[i].tet);
+      n1 = ((abtets[i].ver >> 19) & 8191); // \sum_{i=0^12}{2^i} = 8191
+      edgepivot = (abtets[i].ver & 3); 
+      t = ((abtets[i].ver >> 6) & 8191);
+      if (fc->unflip) {        
+        if (b->verbose > 2) {
+          printf("      Recover a %d-to-m flip at e[%d] of f[%d].\n", n1, 
+                 edgepivot, t);
+        }
+        // Recover the flipped edge ([c,b] or [a,c]).
+        // abtets[(t - 1 + i) % i] is [a,b,e,d], i.e., the tet created by
+        //   the flipping of edge [c,b] or [a,c]. It must still exist in
+        //   Star(ab). Use it to recover the flipped edge.
+        if (edgepivot == 1) { 
+          // The flip edge is [c,b].
+          tmpabtets[0] = abtets[(t - 1 + i) % i]; // [a,b,e,d]
+          eprevself(tmpabtets[0]);
+          esymself(tmpabtets[0]);
+          eprevself(tmpabtets[0]); // [d,a,e,b]
+          fsym(tmpabtets[0], tmpabtets[1]); // [a,d,e,c]
+        } else {
+          // The flip edge is [a,c].
+          tmpabtets[1] = abtets[(t - 1 + i) % i]; // [a,b,e,d]
+          enextself(tmpabtets[1]);
+          esymself(tmpabtets[1]);
+          enextself(tmpabtets[1]); // [b,d,e,a]
+          fsym(tmpabtets[1], tmpabtets[0]); // [d,b,e,c]
+        } // if (edgepivot == 2)
+
+        // Do a n1-to-m1 flip to recover the flipped edge ([c,b] or [a,c]).
+        flipnm_post(tmpabtets, n1, 2, edgepivot, fc);
+
+        // Insert the two recovered tets into the original Star(ab).
+        for (j = i - 1; j >= t; j--) {
+          abtets[j + 1] = abtets[j];  // Downshift
+        }
+        if (edgepivot == 1) {
+          // tmpabtets[0] is [c,b,d,a] ==> contains [a,b]
+          // tmpabtets[1] is [c,b,a,e] ==> contains [a,b]
+          // tmpabtets[2] is [c,b,e,d]
+          fliptets[0] = tmpabtets[1];
+          enextself(fliptets[0]);
+          esymself(fliptets[0]); // [a,b,e,c]
+          fliptets[1] = tmpabtets[0];
+          esymself(fliptets[1]);
+          eprevself(fliptets[1]); // [a,b,c,d]
+        } else {
+          // tmpabtets[0] is [a,c,d,b] ==> contains [a,b]
+          // tmpabtets[1] is [a,c,b,e] ==> contains [a,b]
+          // tmpabtets[2] is [a,c,e,d]
+          fliptets[0] = tmpabtets[1];
+          eprevself(fliptets[0]);
+          esymself(fliptets[0]); // [a,b,e,c]
+          fliptets[1] = tmpabtets[0];
+          esymself(fliptets[1]);
+          enextself(fliptets[1]); // [a,b,c,d]
+        } // edgepivot == 2
+        // Insert the two recovered tets into Star(ab).
+        abtets[((t-1) + (i+1)) % (i+1)] = fliptets[0];
+        abtets[t] = fliptets[1];
+      } 
+      else {
+        // Only free the spaces.
+        flipnm_post(tmpabtets, n1, 2, edgepivot, fc);
+      } // if (!unflip)
+      if (b->verbose > 2) {
+        printf("      Release %d spaces at f[%d].\n", n1, i);
+      }
+      delete [] tmpabtets;
+    }
+  } // i
+
+  return 1;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// insertpoint()    Insert a point into current tetrahedralization.          //
+//                                                                           //
+// The Bowyer-Watson (B-W) algorithm is used to add a new point p into the   //
+// tetrahedralization T. It first finds a "cavity", denoted as C, in T,  C   //
+// consists of tetrahedra in T that "conflict" with p.  If T is a Delaunay   //
+// tetrahedralization, then all boundary faces (triangles) of C are visible  //
+// by p, i.e.,C is star-shaped. We can insert p into T by first deleting all //
+// tetrahedra in C, then creating new tetrahedra formed by boundary faces of //
+// C and p.  If T is not a DT, then C may be not star-shaped.  It must be    //
+// modified so that it becomes star-shaped.                                  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::insertpoint(point insertpt, triface *searchtet, face *splitsh,
+                            face *splitseg, insertvertexflags *ivf)
+{
+  arraypool *swaplist;
+  triface *cavetet, spintet, neightet, neineitet, *parytet;
+  triface oldtet, newtet, newneitet;
+  face checksh, neighsh, *parysh;
+  face checkseg, *paryseg;
+  point *pts, pa, pb, pc, *parypt;
+  enum locateresult loc = OUTSIDE;
+  REAL sign, ori;
+  REAL attrib, volume;
+  bool enqflag;
+  int t1ver;
+  int i, j, k, s;
+
+  if (b->verbose > 2) {
+    printf("      Insert point %d\n", pointmark(insertpt));
+  }
+
+  // Locate the point.
+  if (searchtet->tet != NULL) {
+    loc = (enum locateresult) ivf->iloc;
+  }
+
+  if (loc == OUTSIDE) {
+    if (searchtet->tet == NULL) {
+      if (!b->weighted) {
+        randomsample(insertpt, searchtet);
+      } else {
+        // Weighted DT. There may exist dangling vertex. 
+        *searchtet = recenttet;
+      }
+    }
+    // Locate the point.
+    loc = locate(insertpt, searchtet); 
+  }
+
+  ivf->iloc = (int) loc; // The return value.
+
+  if (b->weighted) {
+    if (loc != OUTSIDE) {
+      // Check if this vertex is regular.
+      pts = (point *) searchtet->tet;
+      sign = orient4d_s(pts[4], pts[5], pts[6], pts[7], insertpt,
+                        pts[4][3], pts[5][3], pts[6][3], pts[7][3],
+                        insertpt[3]);
+      if (sign > 0) {
+        // This new vertex lies above the lower hull. Do not insert it.
+        ivf->iloc = (int) NONREGULAR;
+        return 0;
+      }
+    }
+  }
+
+  // Create the initial cavity C(p) which contains all tetrahedra that
+  //   intersect p. It may include 1, 2, or n tetrahedra.
+  // If p lies on a segment or subface, also create the initial sub-cavity
+  //   sC(p) which contains all subfaces (and segment) which intersect p.
+
+  if (loc == OUTSIDE) {
+    flip14count++;
+    // The current hull will be enlarged.
+    // Add four adjacent boundary tets into list.
+    for (i = 0; i < 4; i++) {
+      decode(searchtet->tet[i], neightet);
+      neightet.ver = epivot[neightet.ver];
+      cavebdrylist->newindex((void **) &parytet);
+      *parytet = neightet;
+    }
+    infect(*searchtet);
+    caveoldtetlist->newindex((void **) &parytet);
+    *parytet = *searchtet;
+  } else if (loc == INTETRAHEDRON) {
+    flip14count++;
+    // Add four adjacent boundary tets into list.
+    for (i = 0; i < 4; i++) {
+      decode(searchtet->tet[i], neightet);
+      neightet.ver = epivot[neightet.ver];
+      cavebdrylist->newindex((void **) &parytet);
+      *parytet = neightet;
+    }
+    infect(*searchtet);
+    caveoldtetlist->newindex((void **) &parytet);
+    *parytet = *searchtet;
+  } else if (loc == ONFACE) {
+    flip26count++;
+    // Add six adjacent boundary tets into list.
+    j = (searchtet->ver & 3); // The current face number.
+    for (i = 1; i < 4; i++) { 
+      decode(searchtet->tet[(j + i) % 4], neightet);
+      neightet.ver = epivot[neightet.ver];
+      cavebdrylist->newindex((void **) &parytet);
+      *parytet = neightet;
+    }
+    decode(searchtet->tet[j], spintet);
+    j = (spintet.ver & 3); // The current face number.
+    for (i = 1; i < 4; i++) {
+      decode(spintet.tet[(j + i) % 4], neightet);
+      neightet.ver = epivot[neightet.ver];
+      cavebdrylist->newindex((void **) &parytet);
+      *parytet = neightet;
+    }
+    infect(spintet);
+    caveoldtetlist->newindex((void **) &parytet);
+    *parytet = spintet;
+    infect(*searchtet);
+    caveoldtetlist->newindex((void **) &parytet);
+    *parytet = *searchtet;
+
+    if (ivf->splitbdflag) { 
+      if ((splitsh != NULL) && (splitsh->sh != NULL)) {
+        // Create the initial sub-cavity sC(p).
+        smarktest(*splitsh);
+        caveshlist->newindex((void **) &parysh);
+        *parysh = *splitsh;
+      }
+    } // if (splitbdflag)
+  } else if (loc == ONEDGE) {
+    flipn2ncount++;
+    // Add all adjacent boundary tets into list.
+    spintet = *searchtet;
+    while (1) {
+      eorgoppo(spintet, neightet);
+      decode(neightet.tet[neightet.ver & 3], neightet);
+      neightet.ver = epivot[neightet.ver];
+      cavebdrylist->newindex((void **) &parytet);
+      *parytet = neightet;
+      edestoppo(spintet, neightet);
+      decode(neightet.tet[neightet.ver & 3], neightet);
+      neightet.ver = epivot[neightet.ver];
+      cavebdrylist->newindex((void **) &parytet);
+      *parytet = neightet;
+      infect(spintet);
+      caveoldtetlist->newindex((void **) &parytet);
+      *parytet = spintet;
+      fnextself(spintet);
+      if (spintet.tet == searchtet->tet) break;
+    } // while (1)
+
+    if (ivf->splitbdflag) {
+      // Create the initial sub-cavity sC(p).
+      if ((splitseg != NULL) && (splitseg->sh != NULL)) {
+        smarktest(*splitseg);
+        splitseg->shver = 0;
+        spivot(*splitseg, *splitsh);
+      }
+      if (splitsh != NULL) {
+        if (splitsh->sh != NULL) {
+          // Collect all subfaces share at this edge.
+          pa = sorg(*splitsh);
+          neighsh = *splitsh;
+          while (1) {
+            // Adjust the origin of its edge to be 'pa'.
+            if (sorg(neighsh) != pa) {
+              sesymself(neighsh);
+            }
+            // Add this face into list (in B-W cavity).
+            smarktest(neighsh);
+            caveshlist->newindex((void **) &parysh);
+            *parysh = neighsh;
+            // Add this face into face-at-splitedge list.
+            cavesegshlist->newindex((void **) &parysh);
+            *parysh = neighsh;
+            // Go to the next face at the edge.
+            spivotself(neighsh);
+            // Stop if all faces at the edge have been visited.
+            if (neighsh.sh == splitsh->sh) break;
+            if (neighsh.sh == NULL) break;
+          } // while (1)
+        } // if (not a dangling segment)
+      }
+    } // if (splitbdflag)
+  } else if (loc == INSTAR) {
+    // We assume that all tets in the star are given in 'caveoldtetlist',
+    //   and they are all infected.
+    // Collect the boundary faces of the star.
+    for (i = 0; i < caveoldtetlist->objects; i++) {
+      cavetet = (triface *) fastlookup(caveoldtetlist, i);
+      // Check its 4 neighbor tets.
+      for (j = 0; j < 4; j++) {
+        decode(cavetet->tet[j], neightet);
+        if (!infected(neightet)) {
+          // It's a boundary face.
+          neightet.ver = epivot[neightet.ver];
+          cavebdrylist->newindex((void **) &parytet);
+          *parytet = neightet;
+        }
+      }
+    }
+  } else if (loc == ONVERTEX) {
+    // The point already exist. Do nothing and return.
+    return 0;
+  } 
+
+
+  if (ivf->bowywat) {
+    // Update the cavity C(p) using the Bowyer-Watson algorithm.
+    swaplist = cavetetlist;
+    cavetetlist = cavebdrylist;
+    cavebdrylist = swaplist;
+    for (i = 0; i < cavetetlist->objects; i++) {
+      // 'cavetet' is an adjacent tet at outside of the cavity.
+      cavetet = (triface *) fastlookup(cavetetlist, i);
+      // The tet may be tested and included in the (enlarged) cavity.
+      if (!infected(*cavetet)) {
+        // Check for two possible cases for this tet: 
+        //   (1) It is a cavity tet, or
+        //   (2) it is a cavity boundary face.
+        enqflag = false;
+        if (!marktested(*cavetet)) {
+          // Do Delaunay (in-sphere) test.
+          pts = (point *) cavetet->tet;
+          if (pts[7] != dummypoint) {
+            // A volume tet. Operate on it.
+            if (b->weighted) {
+              sign = orient4d_s(pts[4], pts[5], pts[6], pts[7], insertpt,
+                                pts[4][3], pts[5][3], pts[6][3], pts[7][3],
+                                insertpt[3]);
+            } else {
+              sign = insphere_s(pts[4], pts[5], pts[6], pts[7], insertpt);
+            }
+            enqflag = (sign < 0.0);
+          } else {
+            if (!nonconvex) {
+              // Test if this hull face is visible by the new point. 
+              ori = orient3d(pts[4], pts[5], pts[6], insertpt); 
+              if (ori < 0) {
+                // A visible hull face. 
+                // Include it in the cavity. The convex hull will be enlarged.
+                enqflag = true; 
+              } else if (ori == 0.0) {
+                // A coplanar hull face. We need to test if this hull face is
+                //   Delaunay or not. We test if the adjacent tet (not faked)
+                //   of this hull face is Delaunay or not.
+                decode(cavetet->tet[3], neineitet);
+                if (!infected(neineitet)) {
+                  if (!marktested(neineitet)) {
+                    // Do Delaunay test on this tet.
+                    pts = (point *) neineitet.tet;
+                    if (b->weighted) {
+                      sign = orient4d_s(pts[4],pts[5],pts[6],pts[7], insertpt,
+                                        pts[4][3], pts[5][3], pts[6][3], 
+                                        pts[7][3], insertpt[3]);
+                    } else {
+                      sign = insphere_s(pts[4],pts[5],pts[6],pts[7], insertpt);
+                    }
+                    enqflag = (sign < 0.0);
+                  } 
+                } else {
+                  // The adjacent tet is non-Delaunay. The hull face is non-
+                  //   Delaunay as well. Include it in the cavity.
+                  enqflag = true;
+                } // if (!infected(neineitet))
+              } // if (ori == 0.0)
+            } else {
+              // A hull face (must be a subface).
+              // We FIRST include it in the initial cavity if the adjacent tet
+              //   (not faked) of this hull face is not Delaunay wrt p.
+              //   Whether it belongs to the final cavity will be determined
+              //   during the validation process. 'validflag'.
+              decode(cavetet->tet[3], neineitet);
+              if (!infected(neineitet)) {
+                if (!marktested(neineitet)) {
+                  // Do Delaunay test on this tet.
+                  pts = (point *) neineitet.tet;
+                  if (b->weighted) {
+                    sign = orient4d_s(pts[4],pts[5],pts[6],pts[7], insertpt,
+                                      pts[4][3], pts[5][3], pts[6][3], 
+                                      pts[7][3], insertpt[3]);
+                  } else {
+                    sign = insphere_s(pts[4],pts[5],pts[6],pts[7], insertpt);
+                  }
+                  enqflag = (sign < 0.0);
+                } 
+              } else {
+                // The adjacent tet is non-Delaunay. The hull face is non-
+                //   Delaunay as well. Include it in the cavity.
+                enqflag = true;
+              } // if (infected(neineitet))
+            } // if (nonconvex)
+          } // if (pts[7] != dummypoint)
+          marktest(*cavetet); // Only test it once.
+        } // if (!marktested(*cavetet))
+
+        if (enqflag) {
+          // Found a tet in the cavity. Put other three faces in check list.
+          k = (cavetet->ver & 3); // The current face number
+          for (j = 1; j < 4; j++) {
+            decode(cavetet->tet[(j + k) % 4], neightet);
+            cavetetlist->newindex((void **) &parytet);
+            *parytet = neightet;
+          }
+          infect(*cavetet);
+          caveoldtetlist->newindex((void **) &parytet);
+          *parytet = *cavetet;
+        } else {
+          // Found a boundary face of the cavity. 
+          cavetet->ver = epivot[cavetet->ver];
+          cavebdrylist->newindex((void **) &parytet);
+          *parytet = *cavetet;
+        }
+      } // if (!infected(*cavetet))
+    } // i
+
+    cavetetlist->restart(); // Clear the working list.
+  } // if (ivf->bowywat)
+
+  if (checksubsegflag) {
+    // Collect all segments of C(p).
+    shellface *ssptr;
+    for (i = 0; i < caveoldtetlist->objects; i++) {
+      cavetet = (triface *) fastlookup(caveoldtetlist, i);
+      if ((ssptr = (shellface*) cavetet->tet[8]) != NULL) {
+        for (j = 0; j < 6; j++) {
+          if (ssptr[j]) {
+            sdecode(ssptr[j], checkseg);
+            if (!sinfected(checkseg)) {
+              sinfect(checkseg);
+              cavetetseglist->newindex((void **) &paryseg);
+              *paryseg = checkseg;
+            }
+          }
+        } // j
+      }
+    } // i
+    // Uninfect collected segments.
+    for (i = 0; i < cavetetseglist->objects; i++) {
+      paryseg = (face *) fastlookup(cavetetseglist, i);
+      suninfect(*paryseg);
+    }
+
+  } // if (checksubsegflag)
+
+  if (checksubfaceflag) {
+    // Collect all subfaces of C(p).
+    shellface *sptr;
+    for (i = 0; i < caveoldtetlist->objects; i++) {
+      cavetet = (triface *) fastlookup(caveoldtetlist, i);
+      if ((sptr = (shellface*) cavetet->tet[9]) != NULL) {
+        for (j = 0; j < 4; j++) {
+          if (sptr[j]) {
+            sdecode(sptr[j], checksh);
+            if (!sinfected(checksh)) {
+              sinfect(checksh);
+              cavetetshlist->newindex((void **) &parysh);
+              *parysh = checksh;
+            }
+          }
+        } // j
+      }
+    } // i
+    // Uninfect collected subfaces.
+    for (i = 0; i < cavetetshlist->objects; i++) {
+      parysh = (face *) fastlookup(cavetetshlist, i);
+      suninfect(*parysh);
+    }
+
+  } // if (checksubfaceflag)
+
+  if ((ivf->iloc == (int) OUTSIDE) && ivf->refineflag) {
+    // The vertex lies outside of the domain. And it does not encroach
+    //   upon any boundary segment or subface. Do not insert it.
+    insertpoint_abort(splitseg, ivf);
+    return 0;
+  }
+
+  if (ivf->splitbdflag) { 
+    // The new point locates in surface mesh. Update the sC(p). 
+    // We have already 'smarktested' the subfaces which directly intersect
+    //   with p in 'caveshlist'. From them, we 'smarktest' their neighboring
+    //   subfaces which are included in C(p). Do not across a segment.
+    for (i = 0; i < caveshlist->objects; i++) {
+      parysh = (face *) fastlookup(caveshlist, i);
+      checksh = *parysh;
+      for (j = 0; j < 3; j++) {
+        if (!isshsubseg(checksh)) {
+          spivot(checksh, neighsh);
+          if (!smarktested(neighsh)) {
+            stpivot(neighsh, neightet);
+            if (infected(neightet)) {
+              fsymself(neightet);
+              if (infected(neightet)) {
+                // This subface is inside C(p). 
+                // Check if its diametrical circumsphere encloses 'p'.
+                //   The purpose of this check is to avoid forming invalid
+                //   subcavity in surface mesh.
+                sign = incircle3d(sorg(neighsh), sdest(neighsh),
+                                  sapex(neighsh), insertpt);
+                if (sign < 0) {
+                  smarktest(neighsh);
+                  caveshlist->newindex((void **) &parysh);
+                  *parysh = neighsh;
+                }
+              }
+            }
+          }
+        }
+        senextself(checksh);
+      } // j
+    } // i
+  } // if (ivf->splitbdflag)
+
+  if (ivf->validflag) {
+    // Validate C(p) and update it if it is not star-shaped.
+    int cutcount = 0;
+
+    if (ivf->respectbdflag) {
+      // The initial cavity may include subfaces which are not on the facets
+      //   being splitting. Find them and make them as boundary of C(p). 
+      // Comment: We have already 'smarktested' the subfaces in sC(p). They
+      //   are completely inside C(p). 
+      for (i = 0; i < cavetetshlist->objects; i++) {
+        parysh = (face *) fastlookup(cavetetshlist, i);
+        stpivot(*parysh, neightet);
+        if (infected(neightet)) {
+          fsymself(neightet);
+          if (infected(neightet)) {
+            // Found a subface inside C(p).
+            if (!smarktested(*parysh)) {
+              // It is possible that this face is a boundary subface.
+              // Check if it is a hull face.
+              //assert(apex(neightet) != dummypoint);
+              if (oppo(neightet) != dummypoint) {
+                fsymself(neightet);
+              }
+              if (oppo(neightet) != dummypoint) {
+                ori = orient3d(org(neightet), dest(neightet), apex(neightet),
+                               insertpt);
+                if (ori < 0) {
+                  // A visible face, get its neighbor face.
+                  fsymself(neightet);
+                  ori = -ori; // It must be invisible by p.
+                }
+              } else {
+                // A hull tet. It needs to be cut.
+                ori = 1;
+              }
+              // Cut this tet if it is either invisible by or coplanar with p.
+              if (ori >= 0) {
+                uninfect(neightet);
+                unmarktest(neightet);
+                cutcount++;
+                neightet.ver = epivot[neightet.ver];
+                cavebdrylist->newindex((void **) &parytet);
+                *parytet = neightet;
+                // Add three new faces to find new boundaries.
+                for (j = 0; j < 3; j++) {
+                  esym(neightet, neineitet);
+                  neineitet.ver = epivot[neineitet.ver];
+                  cavebdrylist->newindex((void **) &parytet);
+                  *parytet = neineitet;
+                  enextself(neightet);
+                }
+              } // if (ori >= 0) 
+            }
+          }
+        }
+      } // i
+
+      // The initial cavity may include segments in its interior. We need to
+      //   Update the cavity so that these segments are on the boundary of
+      //   the cavity.
+      for (i = 0; i < cavetetseglist->objects; i++) {
+        paryseg = (face *) fastlookup(cavetetseglist, i);
+        // Check this segment if it is not a splitting segment.
+        if (!smarktested(*paryseg)) {
+          sstpivot1(*paryseg, neightet);
+          spintet = neightet;
+          while (1) {
+            if (!infected(spintet)) break;
+            fnextself(spintet);
+            if (spintet.tet == neightet.tet) break;
+          }
+          if (infected(spintet)) {
+            // Find an adjacent tet at this segment such that both faces
+            //   at this segment are not visible by p.
+            pa = org(neightet);
+            pb = dest(neightet);
+            spintet = neightet;
+            j = 0;
+            while (1) {
+              // Check if this face is visible by p.
+              pc = apex(spintet);
+              if (pc != dummypoint) {
+                ori = orient3d(pa, pb, pc, insertpt);
+                if (ori >= 0) {
+                  // Not visible. Check another face in this tet.
+                  esym(spintet, neineitet);
+                  pc = apex(neineitet);
+                  if (pc != dummypoint) {
+                    ori = orient3d(pb, pa, pc, insertpt);
+                    if (ori >= 0) {
+                      // Not visible. Found this face.
+                      j = 1; // Flag that it is found.
+                      break;
+                    }
+                  }
+                }
+              }
+              fnextself(spintet);
+              if (spintet.tet == neightet.tet) break;
+            }
+            if (j == 0) {
+              // Not found such a face.
+              terminatetetgen(this, 2); 
+            }
+            neightet = spintet;
+            if (b->verbose > 3) {
+               printf("        Cut tet (%d, %d, %d, %d)\n", 
+                      pointmark(org(neightet)), pointmark(dest(neightet)),
+                      pointmark(apex(neightet)), pointmark(oppo(neightet)));
+            }
+            uninfect(neightet);
+            unmarktest(neightet);
+            cutcount++;
+            neightet.ver = epivot[neightet.ver];
+            cavebdrylist->newindex((void **) &parytet);
+            *parytet = neightet;
+            // Add three new faces to find new boundaries.
+            for (j = 0; j < 3; j++) {
+              esym(neightet, neineitet);
+              neineitet.ver = epivot[neineitet.ver];
+              cavebdrylist->newindex((void **) &parytet);
+              *parytet = neineitet;
+              enextself(neightet);
+            }
+          }
+        }
+      } // i
+    } // if (ivf->respectbdflag)
+
+    // Update the cavity by removing invisible faces until it is star-shaped.
+    for (i = 0; i < cavebdrylist->objects; i++) {
+      cavetet = (triface *) fastlookup(cavebdrylist, i);
+      // 'cavetet' is an exterior tet adjacent to the cavity.
+      // Check if its neighbor is inside C(p).
+      fsym(*cavetet, neightet);
+      if (infected(neightet)) {        
+        if (apex(*cavetet) != dummypoint) {
+          // It is a cavity boundary face. Check its visibility.
+          if (oppo(neightet) != dummypoint) {
+            // Check if this face is visible by the new point.
+            if (issubface(neightet)) {
+              // We should only create a new tet that has a reasonable volume.
+              // Re-use 'volume' and 'attrib'.
+              pa = org(*cavetet);
+              pb = dest(*cavetet);
+              pc = apex(*cavetet);
+              volume = orient3dfast(pa, pb, pc, insertpt);
+              attrib = distance(pa, pb) * distance(pb, pc) * distance(pc, pa);
+              if ((fabs(volume) / attrib) < b->epsilon) {
+                ori = 0.0;
+              } else {
+                ori = orient3d(pa, pb, pc, insertpt); 
+              }
+            } else {
+              ori = orient3d(org(*cavetet), dest(*cavetet), apex(*cavetet),
+                             insertpt); 
+            }
+            enqflag = (ori > 0);
+            // Comment: if ori == 0 (coplanar case), we also cut the tet.
+          } else {
+            // It is a hull face. And its adjacent tet (at inside of the 
+            //   domain) has been cut from the cavity. Cut it as well.
+            //assert(nonconvex);
+            enqflag = false;
+          }
+        } else {
+          enqflag = true; // A hull edge.
+        }
+        if (enqflag) {
+          // This face is valid, save it.
+          cavetetlist->newindex((void **) &parytet);
+          *parytet = *cavetet; 
+        } else {
+          uninfect(neightet);
+          unmarktest(neightet);
+          cutcount++;
+          // Add three new faces to find new boundaries.
+          for (j = 0; j < 3; j++) {
+            esym(neightet, neineitet);
+            neineitet.ver = epivot[neineitet.ver];
+            cavebdrylist->newindex((void **) &parytet);
+            *parytet = neineitet;
+            enextself(neightet);
+          }
+          // 'cavetet' is not on the cavity boundary anymore.
+          unmarktest(*cavetet);
+        }
+      } else {
+        // 'cavetet' is not on the cavity boundary anymore.
+        unmarktest(*cavetet);
+      }
+    } // i
+
+    if (cutcount > 0) {
+      // The cavity has been updated.
+      // Update the cavity boundary faces.
+      cavebdrylist->restart();
+      for (i = 0; i < cavetetlist->objects; i++) {
+        cavetet = (triface *) fastlookup(cavetetlist, i);
+        // 'cavetet' was an exterior tet adjacent to the cavity.
+        fsym(*cavetet, neightet);
+        if (infected(neightet)) {
+          // It is a cavity boundary face.
+          cavebdrylist->newindex((void **) &parytet);
+          *parytet = *cavetet;
+        } else {
+          // Not a cavity boundary face.
+          unmarktest(*cavetet);
+        }
+      }
+
+      // Update the list of old tets.
+      cavetetlist->restart();
+      for (i = 0; i < caveoldtetlist->objects; i++) {
+        cavetet = (triface *) fastlookup(caveoldtetlist, i);
+        if (infected(*cavetet)) {
+          cavetetlist->newindex((void **) &parytet);
+          *parytet = *cavetet;
+        }
+      }
+      // Swap 'cavetetlist' and 'caveoldtetlist'.
+      swaplist = caveoldtetlist;
+      caveoldtetlist = cavetetlist;
+      cavetetlist = swaplist;
+
+      // The cavity should contain at least one tet.
+      if (caveoldtetlist->objects == 0l) {
+        insertpoint_abort(splitseg, ivf);
+        ivf->iloc = (int) BADELEMENT;
+        return 0;
+      }
+
+      if (ivf->splitbdflag) { 
+        int cutshcount = 0;
+        // Update the sub-cavity sC(p).
+        for (i = 0; i < caveshlist->objects; i++) {
+          parysh = (face *) fastlookup(caveshlist, i);
+          if (smarktested(*parysh)) {
+            enqflag = false;
+            stpivot(*parysh, neightet);
+            if (infected(neightet)) {
+              fsymself(neightet);
+              if (infected(neightet)) {
+                enqflag = true;
+              }
+            }
+            if (!enqflag) {
+              sunmarktest(*parysh);
+              // Use the last entry of this array to fill this entry.
+              j = caveshlist->objects - 1;
+              checksh = * (face *) fastlookup(caveshlist, j);
+              *parysh = checksh;
+              cutshcount++;
+              caveshlist->objects--; // The list is shrinked.
+              i--;
+            }
+          }
+        }
+
+        if (cutshcount > 0) {
+          i = 0; // Count the number of invalid subfaces/segments.
+          // Valid the updated sub-cavity sC(p).
+          if (loc == ONFACE) {
+            if ((splitsh != NULL) && (splitsh->sh != NULL)) {
+              // The to-be split subface should be in sC(p).
+              if (!smarktested(*splitsh)) i++;
+            }
+          } else if (loc == ONEDGE) {
+            if ((splitseg != NULL) && (splitseg->sh != NULL)) {
+              // The to-be split segment should be in sC(p).
+              if (!smarktested(*splitseg)) i++;
+            }
+            if ((splitsh != NULL) && (splitsh->sh != NULL)) {
+              // All subfaces at this edge should be in sC(p).
+              pa = sorg(*splitsh);
+              neighsh = *splitsh;
+              while (1) {
+                // Adjust the origin of its edge to be 'pa'.
+                if (sorg(neighsh) != pa) {
+                  sesymself(neighsh);
+                }
+                // Add this face into list (in B-W cavity).
+                if (!smarktested(neighsh)) i++;
+                // Go to the next face at the edge.
+                spivotself(neighsh);
+                // Stop if all faces at the edge have been visited.
+                if (neighsh.sh == splitsh->sh) break;
+                if (neighsh.sh == NULL) break;
+              } // while (1)
+            }
+          }
+
+          if (i > 0) {
+            // The updated sC(p) is invalid. Do not insert this vertex.
+            insertpoint_abort(splitseg, ivf);
+            ivf->iloc = (int) BADELEMENT;
+            return 0;
+          }
+        } // if (cutshcount > 0)
+      } // if (ivf->splitbdflag)
+    } // if (cutcount > 0)
+
+  } // if (ivf->validflag)
+
+  if (ivf->refineflag) {
+    // The new point is inserted by Delaunay refinement, i.e., it is the 
+    //   circumcenter of a tetrahedron, or a subface, or a segment.
+    //   Do not insert this point if the tetrahedron, or subface, or segment
+    //   is not inside the final cavity.
+    if (((ivf->refineflag == 1) && !infected(ivf->refinetet)) ||
+        ((ivf->refineflag == 2) && !smarktested(ivf->refinesh))) {
+      insertpoint_abort(splitseg, ivf);
+      ivf->iloc = (int) BADELEMENT;
+      return 0;
+    }
+  } // if (ivf->refineflag)
+
+  if (b->plc && (loc != INSTAR)) {
+    // Reject the new point if it lies too close to an existing point (b->plc),
+    // or it lies inside a protecting ball of near vertex (ivf->rejflag & 4).
+    // Collect the list of vertices of the initial cavity.
+    if (loc == OUTSIDE) {
+      pts = (point *) &(searchtet->tet[4]);
+      for (i = 0; i < 3; i++) {
+        cavetetvertlist->newindex((void **) &parypt);
+        *parypt = pts[i];
+      }
+    } else if (loc == INTETRAHEDRON) {
+      pts = (point *) &(searchtet->tet[4]);
+      for (i = 0; i < 4; i++) {
+        cavetetvertlist->newindex((void **) &parypt);
+        *parypt = pts[i];
+      } 
+    } else if (loc == ONFACE) {
+      pts = (point *) &(searchtet->tet[4]);
+      for (i = 0; i < 3; i++) {
+        cavetetvertlist->newindex((void **) &parypt);
+        *parypt = pts[i];
+      }
+      if (pts[3] != dummypoint) {
+        cavetetvertlist->newindex((void **) &parypt);
+        *parypt = pts[3];
+      }
+      fsym(*searchtet, spintet);
+      if (oppo(spintet) != dummypoint) {
+        cavetetvertlist->newindex((void **) &parypt);
+        *parypt = oppo(spintet);
+      }
+    } else if (loc == ONEDGE) {
+      spintet = *searchtet;
+      cavetetvertlist->newindex((void **) &parypt);
+      *parypt = org(spintet);
+      cavetetvertlist->newindex((void **) &parypt);
+      *parypt = dest(spintet);
+      while (1) {
+        if (apex(spintet) != dummypoint) {
+          cavetetvertlist->newindex((void **) &parypt);
+          *parypt = apex(spintet);
+        }
+        fnextself(spintet);
+        if (spintet.tet == searchtet->tet) break;
+      }
+    }
+
+    int rejptflag = (ivf->rejflag & 4);
+    REAL rd;
+    pts = NULL;
+
+    for (i = 0; i < cavetetvertlist->objects; i++) {
+      parypt = (point *) fastlookup(cavetetvertlist, i);
+      rd = distance(*parypt, insertpt);
+      // Is the point very close to an existing point?
+      if (rd < minedgelength) {
+        pts = parypt; 
+        loc = NEARVERTEX;
+        break;
+      }
+      if (rejptflag) {
+        // Is the point encroaches upon an existing point?
+        if (rd < (0.5 * (*parypt)[pointmtrindex])) {
+          pts = parypt;
+          loc = ENCVERTEX; 
+          break;
+        }
+      }
+    }
+    cavetetvertlist->restart(); // Clear the work list.
+
+    if (pts != NULL) {
+      // The point is either too close to an existing vertex (NEARVERTEX)
+      //   or encroaches upon (inside the protecting ball) of that vertex.
+      if (loc == NEARVERTEX) {
+        if (!issteinerpoint(insertpt) && b->nomergevertex) { // -M0/1 option.
+          // 'insertpt' is an input vertex. 
+          // In this case, we still insert this vertex. Issue a warning.
+          if (!b->quiet) {
+            printf("Warning:  Two points, %d and %d, are very close.\n",
+                   pointmark(insertpt), pointmark(*pts));
+            printf("  Creating a very short edge (len = %g) (< %g).\n",
+                   rd, minedgelength);
+            printf("  You may try a smaller tolerance (-T) (current is %g)\n", 
+                   b->epsilon);
+            printf("  to avoid this warning.\n");
+          }
+        } else {
+          point2tetorg(*pts, *searchtet);
+          insertpoint_abort(splitseg, ivf);
+          ivf->iloc = (int) loc;
+          return 0;
+        }
+      } else { // loc == ENCVERTEX
+        // The point lies inside the protection ball.
+        point2tetorg(*pts, *searchtet); 
+        insertpoint_abort(splitseg, ivf);
+        ivf->iloc = (int) loc;
+        return 0;
+      }
+    }
+  } // if (b->plc && (loc != INSTAR))
+
+  if (b->weighted || ivf->cdtflag || ivf->smlenflag
+      ) {
+    // There may be other vertices inside C(p). We need to find them.
+    // Collect all vertices of C(p).
+    for (i = 0; i < caveoldtetlist->objects; i++) {
+      cavetet = (triface *) fastlookup(caveoldtetlist, i);
+      //assert(infected(*cavetet));
+      pts = (point *) &(cavetet->tet[4]);
+      for (j = 0; j < 4; j++) {
+        if (pts[j] != dummypoint) {
+          if (!pinfected(pts[j])) {
+            pinfect(pts[j]);
+            cavetetvertlist->newindex((void **) &parypt);
+            *parypt = pts[j];
+          }
+        }
+      } // j
+    } // i
+    // Uninfect all collected (cavity) vertices.
+    for (i = 0; i < cavetetvertlist->objects; i++) {
+      parypt = (point *) fastlookup(cavetetvertlist, i);
+      puninfect(*parypt);
+    }
+    if (ivf->smlenflag) {
+      REAL len;
+      // Get the length of the shortest edge connecting to 'newpt'.
+      parypt = (point *) fastlookup(cavetetvertlist, 0);
+      ivf->smlen = distance(*parypt, insertpt);
+      ivf->parentpt = *parypt;
+      for (i = 1; i < cavetetvertlist->objects; i++) {
+        parypt = (point *) fastlookup(cavetetvertlist, i);
+        len = distance(*parypt, insertpt);
+        if (len < ivf->smlen) {
+          ivf->smlen = len;
+          ivf->parentpt = *parypt;
+        }
+      } 
+    }
+  }
+
+
+  if (ivf->cdtflag) {
+    // Unmark tets.
+    for (i = 0; i < caveoldtetlist->objects; i++) {
+      cavetet = (triface *) fastlookup(caveoldtetlist, i);
+      unmarktest(*cavetet);
+    }
+    for (i = 0; i < cavebdrylist->objects; i++) {
+      cavetet = (triface *) fastlookup(cavebdrylist, i);
+      unmarktest(*cavetet);
+    }
+    // Clean up arrays which are not needed.
+    cavetetlist->restart();
+    if (checksubsegflag) {
+      cavetetseglist->restart();
+    }
+    if (checksubfaceflag) {
+      cavetetshlist->restart();
+    }
+    return 1;
+  }
+
+  // Before re-mesh C(p). Process the segments and subfaces which are on the
+  //   boundary of C(p). Make sure that each such segment or subface is
+  //   connecting to a tet outside C(p). So we can re-connect them to the
+  //   new tets inside the C(p) later.
+
+  if (checksubsegflag) {
+    for (i = 0; i < cavetetseglist->objects; i++) {
+      paryseg = (face *) fastlookup(cavetetseglist, i);
+      // Operate on it if it is not the splitting segment, i.e., in sC(p).
+      if (!smarktested(*paryseg)) {
+        // Check if the segment is inside the cavity.
+        //   'j' counts the num of adjacent tets of this seg.
+        //   'k' counts the num of adjacent tets which are 'sinfected'.
+        j = k = 0;
+        sstpivot1(*paryseg, neightet);
+        spintet = neightet;
+        while (1) {
+          j++;
+          if (!infected(spintet)) {
+            neineitet = spintet; // An outer tet. Remember it.
+          } else {
+            k++; // An in tet.
+          }
+          fnextself(spintet);
+          if (spintet.tet == neightet.tet) break;
+        }
+        // assert(j > 0);
+        if (k == 0) {
+          // The segment is not connect to C(p) anymore. Remove it by
+          //   Replacing it by the last entry of this list.
+          s = cavetetseglist->objects - 1;
+          checkseg = * (face *) fastlookup(cavetetseglist, s);
+          *paryseg = checkseg;
+          cavetetseglist->objects--;
+          i--;
+        } else if (k < j) {
+          // The segment is on the boundary of C(p).
+          sstbond1(*paryseg, neineitet);
+        } else { // k == j
+          // The segment is inside C(p).
+          if (!ivf->splitbdflag) {
+            checkseg = *paryseg;
+            sinfect(checkseg); // Flag it as an interior segment.
+            caveencseglist->newindex((void **) &paryseg);
+            *paryseg = checkseg;
+          } else {
+            //assert(0); // Not possible.
+            terminatetetgen(this, 2);
+          }
+        }
+      } else { 
+        // assert(smarktested(*paryseg));
+        // Flag it as an interior segment. Do not queue it, since it will
+        //   be deleted after the segment splitting.
+        sinfect(*paryseg);
+      }
+    } // i
+  } // if (checksubsegflag)
+
+  if (checksubfaceflag) {
+    for (i = 0; i < cavetetshlist->objects; i++) {
+      parysh = (face *) fastlookup(cavetetshlist, i);
+      // Operate on it if it is not inside the sub-cavity sC(p).
+      if (!smarktested(*parysh)) {
+        // Check if this subface is inside the cavity.
+        k = 0;
+        for (j = 0; j < 2; j++) {
+          stpivot(*parysh, neightet);
+          if (!infected(neightet)) {
+            checksh = *parysh; // Remember this side.
+          } else {
+            k++;
+          }
+          sesymself(*parysh);
+        }
+        if (k == 0) {
+          // The subface is not connected to C(p). Remove it.
+          s = cavetetshlist->objects - 1;
+          checksh = * (face *) fastlookup(cavetetshlist, s);
+          *parysh = checksh;
+          cavetetshlist->objects--;
+          i--;
+        } else if (k == 1) {
+          // This side is the outer boundary of C(p).
+          *parysh = checksh;
+        } else { // k == 2
+          if (!ivf->splitbdflag) {
+            checksh = *parysh;
+            sinfect(checksh); // Flag it.
+            caveencshlist->newindex((void **) &parysh);
+            *parysh = checksh;
+          } else {
+            //assert(0); // Not possible.
+            terminatetetgen(this, 2);
+          }
+        }
+      } else {
+        // assert(smarktested(*parysh));
+        // Flag it as an interior subface. Do not queue it. It will be
+        //   deleted after the facet point insertion.
+        sinfect(*parysh);
+      }
+    } // i
+  } // if (checksubfaceflag)
+
+  // Create new tetrahedra to fill the cavity.
+
+  for (i = 0; i < cavebdrylist->objects; i++) {
+    cavetet = (triface *) fastlookup(cavebdrylist, i);
+    neightet = *cavetet;
+    unmarktest(neightet); // Unmark it.
+    // Get the oldtet (inside the cavity).
+    fsym(neightet, oldtet);
+    if (apex(neightet) != dummypoint) {
+      // Create a new tet in the cavity.
+      maketetrahedron(&newtet);
+      setorg(newtet, dest(neightet));
+      setdest(newtet, org(neightet));
+      setapex(newtet, apex(neightet));
+      setoppo(newtet, insertpt);
+    } else {
+      // Create a new hull tet.
+      hullsize++; 
+      maketetrahedron(&newtet);
+      setorg(newtet, org(neightet));
+      setdest(newtet, dest(neightet));
+      setapex(newtet, insertpt);
+      setoppo(newtet, dummypoint); // It must opposite to face 3.
+      // Adjust back to the cavity bounday face.
+      esymself(newtet);
+    }
+    // The new tet inherits attribtes from the old tet.
+    for (j = 0; j < numelemattrib; j++) {
+      attrib = elemattribute(oldtet.tet, j);
+      setelemattribute(newtet.tet, j, attrib);
+    }
+    if (b->varvolume) {
+      volume = volumebound(oldtet.tet);
+      setvolumebound(newtet.tet, volume);
+    }
+    // Connect newtet <==> neightet, this also disconnect the old bond.
+    bond(newtet, neightet);
+    // oldtet still connects to neightet.
+    *cavetet = oldtet; // *cavetet = newtet;
+  } // i
+
+  // Set a handle for speeding point location.
+  recenttet = newtet;
+  //setpoint2tet(insertpt, encode(newtet));
+  setpoint2tet(insertpt, (tetrahedron) (newtet.tet));
+
+  // Re-use this list to save new interior cavity faces.
+  cavetetlist->restart();
+
+  // Connect adjacent new tetrahedra together.
+  for (i = 0; i < cavebdrylist->objects; i++) {
+    cavetet = (triface *) fastlookup(cavebdrylist, i);
+    // cavtet is an oldtet, get the newtet at this face.
+    oldtet = *cavetet;
+    fsym(oldtet, neightet);
+    fsym(neightet, newtet);
+    // Comment: oldtet and newtet must be at the same directed edge.
+    // Connect the three other faces of this newtet.
+    for (j = 0; j < 3; j++) {
+      esym(newtet, neightet); // Go to the face.
+      if (neightet.tet[neightet.ver & 3] == NULL) {
+        // Find the adjacent face of this newtet.
+        spintet = oldtet;
+        while (1) {
+          fnextself(spintet);
+          if (!infected(spintet)) break;
+        }
+        fsym(spintet, newneitet);
+        esymself(newneitet);
+        bond(neightet, newneitet);
+        if (ivf->lawson > 1) { 
+          cavetetlist->newindex((void **) &parytet);
+          *parytet = neightet;
+        }
+      }
+      //setpoint2tet(org(newtet), encode(newtet));
+      setpoint2tet(org(newtet), (tetrahedron) (newtet.tet));
+      enextself(newtet);
+      enextself(oldtet);
+    }
+    *cavetet = newtet; // Save the new tet.
+  } // i
+
+  if (checksubfaceflag) {
+    // Connect subfaces on the boundary of the cavity to the new tets.
+    for (i = 0; i < cavetetshlist->objects; i++) {
+      parysh = (face *) fastlookup(cavetetshlist, i);
+      // Connect it if it is not a missing subface.
+      if (!sinfected(*parysh)) {
+        stpivot(*parysh, neightet);
+        fsym(neightet, spintet);
+        sesymself(*parysh);
+        tsbond(spintet, *parysh);
+      }
+    }
+  }
+
+  if (checksubsegflag) {
+    // Connect segments on the boundary of the cavity to the new tets.
+    for (i = 0; i < cavetetseglist->objects; i++) {
+      paryseg = (face *) fastlookup(cavetetseglist, i);
+      // Connect it if it is not a missing segment.
+      if (!sinfected(*paryseg)) {
+        sstpivot1(*paryseg, neightet);
+        spintet = neightet;
+        while (1) {
+          tssbond1(spintet, *paryseg);
+          fnextself(spintet);
+          if (spintet.tet == neightet.tet) break;
+        }
+      }
+    }
+  }
+
+  if (((splitsh != NULL) && (splitsh->sh != NULL)) ||
+      ((splitseg != NULL) && (splitseg->sh != NULL))) {
+    // Split a subface or a segment.
+    sinsertvertex(insertpt, splitsh, splitseg, ivf->sloc, ivf->sbowywat, 0);
+  }
+
+  if (checksubfaceflag) {
+    if (ivf->splitbdflag) {
+      // Recover new subfaces in C(p).
+      for (i = 0; i < caveshbdlist->objects; i++) {
+        // Get an old subface at edge [a, b].
+        parysh = (face *) fastlookup(caveshbdlist, i);
+        spivot(*parysh, checksh); // The new subface [a, b, p].
+        // Do not recover a deleted new face (degenerated).
+        if (checksh.sh[3] != NULL) {
+          // Note that the old subface still connects to adjacent old tets 
+          //   of C(p), which still connect to the tets outside C(p).
+          stpivot(*parysh, neightet);
+          // Find the adjacent tet containing the edge [a,b] outside C(p).
+          spintet = neightet;
+          while (1) {
+            fnextself(spintet);
+            if (!infected(spintet)) break;
+          }
+          // The adjacent tet connects to a new tet in C(p).
+          fsym(spintet, neightet);
+          // Find the tet containing the face [a, b, p].
+          spintet = neightet;
+          while (1) {
+            fnextself(spintet);
+            if (apex(spintet) == insertpt) break;
+          }
+          // Adjust the edge direction in spintet and checksh.
+          if (sorg(checksh) != org(spintet)) {
+            sesymself(checksh);
+          }
+          // Connect the subface to two adjacent tets.
+          tsbond(spintet, checksh);
+          fsymself(spintet);
+          sesymself(checksh);
+          tsbond(spintet, checksh);
+        } // if (checksh.sh[3] != NULL)
+      }
+    } else { 
+      // The Boundary recovery phase.
+      // Put all new subfaces into stack for recovery.
+      for (i = 0; i < caveshbdlist->objects; i++) {
+        // Get an old subface at edge [a, b].
+        parysh = (face *) fastlookup(caveshbdlist, i);
+        spivot(*parysh, checksh); // The new subface [a, b, p].
+        // Do not recover a deleted new face (degenerated).
+        if (checksh.sh[3] != NULL) {
+          subfacstack->newindex((void **) &parysh);
+          *parysh = checksh;
+        }
+      }
+      // Put all interior subfaces into stack for recovery.
+      for (i = 0; i < caveencshlist->objects; i++) {
+        parysh = (face *) fastlookup(caveencshlist, i);
+        // Some subfaces inside C(p) might be split in sinsertvertex().
+        //   Only queue those faces which are not split.
+        if (!smarktested(*parysh)) {
+          checksh = *parysh;
+          suninfect(checksh);
+          stdissolve(checksh); // Detach connections to old tets.
+          subfacstack->newindex((void **) &parysh);
+          *parysh = checksh;
+        }
+      }
+    }
+  } // if (checksubfaceflag)
+
+  if (checksubsegflag) {
+    if (ivf->splitbdflag) {
+      if (splitseg != NULL) {
+        // Recover the two new subsegments in C(p).
+        for (i = 0; i < cavesegshlist->objects; i++) {
+          paryseg = (face *) fastlookup(cavesegshlist, i);
+          // Insert this subsegment into C(p).
+          checkseg = *paryseg;
+          // Get the adjacent new subface.
+          checkseg.shver = 0;
+          spivot(checkseg, checksh);
+          if (checksh.sh != NULL) {
+            // Get the adjacent new tetrahedron.
+            stpivot(checksh, neightet);
+          } else {
+            // It's a dangling segment.
+            point2tetorg(sorg(checkseg), neightet);
+            finddirection(&neightet, sdest(checkseg));
+          }
+          sstbond1(checkseg, neightet);
+          spintet = neightet;
+          while (1) {
+            tssbond1(spintet, checkseg);
+            fnextself(spintet);
+            if (spintet.tet == neightet.tet) break;
+          }
+        }
+      } // if (splitseg != NULL)
+    } else {
+      // The Boundary Recovery Phase.  
+      // Queue missing segments in C(p) for recovery.
+      if (splitseg != NULL) {
+        // Queue two new subsegments in C(p) for recovery.
+        for (i = 0; i < cavesegshlist->objects; i++) {
+          paryseg = (face *) fastlookup(cavesegshlist, i);
+          checkseg = *paryseg;
+          //sstdissolve1(checkseg); // It has not been connected yet.
+          s = randomnation(subsegstack->objects + 1);
+          subsegstack->newindex((void **) &paryseg);
+          *paryseg = * (face *) fastlookup(subsegstack, s); 
+          paryseg = (face *) fastlookup(subsegstack, s);
+          *paryseg = checkseg;
+        }
+      } // if (splitseg != NULL)
+      for (i = 0; i < caveencseglist->objects; i++) {
+        paryseg = (face *) fastlookup(caveencseglist, i);
+        if (!smarktested(*paryseg)) { // It may be split.
+          checkseg = *paryseg;
+          suninfect(checkseg);
+          sstdissolve1(checkseg); // Detach connections to old tets.
+          s = randomnation(subsegstack->objects + 1);
+          subsegstack->newindex((void **) &paryseg);
+          *paryseg = * (face *) fastlookup(subsegstack, s); 
+          paryseg = (face *) fastlookup(subsegstack, s);
+          *paryseg = checkseg;
+        }
+      }
+    }
+  } // if (checksubsegflag)
+
+  if (b->weighted
+      ) {
+    // Some vertices may be completed inside the cavity. They must be
+    //   detected and added to recovering list.
+    // Since every "live" vertex must contain a pointer to a non-dead
+    //   tetrahedron, we can check for each vertex this pointer.
+    for (i = 0; i < cavetetvertlist->objects; i++) {
+      pts = (point *) fastlookup(cavetetvertlist, i);
+      decode(point2tet(*pts), *searchtet);
+      if (infected(*searchtet)) {
+        if (b->weighted) {
+          if (b->verbose > 1) {
+            printf("    Point #%d is non-regular after the insertion of #%d.\n",
+                   pointmark(*pts), pointmark(insertpt));
+          }
+          setpointtype(*pts, NREGULARVERTEX);
+          nonregularcount++;
+        }
+      }
+    }
+  }
+
+  if (ivf->chkencflag & 1) {
+    // Queue all segment outside C(p).
+    for (i = 0; i < cavetetseglist->objects; i++) {
+      paryseg = (face *) fastlookup(cavetetseglist, i);
+      // Skip if it is the split segment.
+      if (!sinfected(*paryseg)) {
+        enqueuesubface(badsubsegs, paryseg);
+      }
+    }
+    if (splitseg != NULL) {
+      // Queue the two new subsegments inside C(p).
+      for (i = 0; i < cavesegshlist->objects; i++) {
+        paryseg = (face *) fastlookup(cavesegshlist, i);
+        enqueuesubface(badsubsegs, paryseg);
+      }
+    }
+  } // if (chkencflag & 1)
+
+  if (ivf->chkencflag & 2) {
+    // Queue all subfaces outside C(p).
+    for (i = 0; i < cavetetshlist->objects; i++) {
+      parysh = (face *) fastlookup(cavetetshlist, i);
+      // Skip if it is a split subface.
+      if (!sinfected(*parysh)) {
+        enqueuesubface(badsubfacs, parysh);
+      }
+    }
+    // Queue all new subfaces inside C(p).
+    for (i = 0; i < caveshbdlist->objects; i++) {
+      // Get an old subface at edge [a, b].
+      parysh = (face *) fastlookup(caveshbdlist, i);
+      spivot(*parysh, checksh); // checksh is a new subface [a, b, p].
+      // Do not recover a deleted new face (degenerated).
+      if (checksh.sh[3] != NULL) {
+        enqueuesubface(badsubfacs, &checksh);
+      }
+    }
+  } // if (chkencflag & 2)
+
+  if (ivf->chkencflag & 4) {
+    // Queue all new tetrahedra in C(p).
+    for (i = 0; i < cavebdrylist->objects; i++) {
+      cavetet = (triface *) fastlookup(cavebdrylist, i);
+      enqueuetetrahedron(cavetet);
+    }
+  }
+
+  // C(p) is re-meshed successfully.
+
+  // Delete the old tets in C(p).
+  for (i = 0; i < caveoldtetlist->objects; i++) {
+    searchtet = (triface *) fastlookup(caveoldtetlist, i);
+    if (ishulltet(*searchtet)) {
+      hullsize--;
+    }
+    tetrahedrondealloc(searchtet->tet);
+  }
+
+  if (((splitsh != NULL) && (splitsh->sh != NULL)) ||
+      ((splitseg != NULL) && (splitseg->sh != NULL))) {
+    // Delete the old subfaces in sC(p).
+    for (i = 0; i < caveshlist->objects; i++) {
+      parysh = (face *) fastlookup(caveshlist, i);
+      if (checksubfaceflag) {//if (bowywat == 2) {
+        // It is possible that this subface still connects to adjacent
+        //   tets which are not in C(p). If so, clear connections in the
+        //   adjacent tets at this subface.
+        stpivot(*parysh, neightet);
+        if (neightet.tet != NULL) {
+          if (neightet.tet[4] != NULL) {
+            // Found an adjacent tet. It must be not in C(p).
+            tsdissolve(neightet);
+            fsymself(neightet);
+            tsdissolve(neightet);
+          }
+        }
+      }
+      shellfacedealloc(subfaces, parysh->sh);
+    }
+    if ((splitseg != NULL) && (splitseg->sh != NULL)) {
+      // Delete the old segment in sC(p).
+      shellfacedealloc(subsegs, splitseg->sh);
+    }
+  }
+
+  if (ivf->lawson) {
+    for (i = 0; i < cavebdrylist->objects; i++) {
+      searchtet = (triface *) fastlookup(cavebdrylist, i);
+      flippush(flipstack, searchtet);
+    }
+    if (ivf->lawson > 1) {
+      for (i = 0; i < cavetetlist->objects; i++) {
+        searchtet = (triface *) fastlookup(cavetetlist, i);
+        flippush(flipstack, searchtet);
+      }
+    }
+  }
+
+
+  // Clean the working lists.
+
+  caveoldtetlist->restart();
+  cavebdrylist->restart();
+  cavetetlist->restart();
+
+  if (checksubsegflag) {
+    cavetetseglist->restart();
+    caveencseglist->restart();
+  }
+
+  if (checksubfaceflag) {
+    cavetetshlist->restart();
+    caveencshlist->restart();
+  }
+  
+  if (b->weighted || ivf->smlenflag
+      ) { 
+    cavetetvertlist->restart();
+  }
+  
+  if (((splitsh != NULL) && (splitsh->sh != NULL)) ||
+      ((splitseg != NULL) && (splitseg->sh != NULL))) {
+    caveshlist->restart();
+    caveshbdlist->restart();
+    cavesegshlist->restart();
+  }
+
+  return 1; // Point is inserted.
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// insertpoint_abort()    Abort the insertion of a new vertex.               //
+//                                                                           //
+// The cavity will be restored.  All working lists are cleared.              //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::insertpoint_abort(face *splitseg, insertvertexflags *ivf)
+{
+  triface *cavetet;
+  face *parysh;
+  int i;
+
+  for (i = 0; i < caveoldtetlist->objects; i++) {
+    cavetet = (triface *) fastlookup(caveoldtetlist, i);
+    uninfect(*cavetet);
+    unmarktest(*cavetet);
+  }
+  for (i = 0; i < cavebdrylist->objects; i++) {
+    cavetet = (triface *) fastlookup(cavebdrylist, i);
+    unmarktest(*cavetet); 
+  }
+  cavetetlist->restart();
+  cavebdrylist->restart();
+  caveoldtetlist->restart();
+  cavetetseglist->restart();
+  cavetetshlist->restart();
+  if (ivf->splitbdflag) { 
+    if ((splitseg != NULL) && (splitseg->sh != NULL)) {
+      sunmarktest(*splitseg);
+    }
+    for (i = 0; i < caveshlist->objects; i++) {
+      parysh = (face *) fastlookup(caveshlist, i);
+      sunmarktest(*parysh);
+    }
+    caveshlist->restart();
+    cavesegshlist->restart();
+  }
+}
+
+////                                                                       ////
+////                                                                       ////
+//// flip_cxx /////////////////////////////////////////////////////////////////
+
+//// delaunay_cxx /////////////////////////////////////////////////////////////
+////                                                                       ////
+////                                                                       ////
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// hilbert_init()    Initialize the Gray code permutation table.             //
+//                                                                           //
+// The table 'transgc' has 8 x 3 x 8 entries. It contains all possible Gray  //
+// code sequences traveled by the 1st order Hilbert curve in 3 dimensions.   //
+// The first column is the Gray code of the entry point of the curve, and    //
+// the second column is the direction (0, 1, or 2, 0 means the x-axis) where //
+// the exit point of curve lies.                                             //
+//                                                                           //
+// The table 'tsb1mod3' contains the numbers of trailing set '1' bits of the //
+// indices from 0 to 7, modulo by '3'. The code for generating this table is //
+// from: http://graphics.stanford.edu/~seander/bithacks.html.                //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::hilbert_init(int n)
+{
+  int gc[8], N, mask, travel_bit;
+  int e, d, f, k, g;
+  int v, c;
+  int i;
+
+  N = (n == 2) ? 4 : 8;
+  mask = (n == 2) ? 3 : 7;
+
+  // Generate the Gray code sequence.
+  for (i = 0; i < N; i++) {
+    gc[i] = i ^ (i >> 1);
+  }
+
+  for (e = 0; e < N; e++) {
+    for (d = 0; d < n; d++) {
+      // Calculate the end point (f).
+      f = e ^ (1 << d);  // Toggle the d-th bit of 'e'.
+      // travel_bit = 2**p, the bit we want to travel. 
+      travel_bit = e ^ f;
+      for (i = 0; i < N; i++) {
+        // // Rotate gc[i] left by (p + 1) % n bits.
+        k = gc[i] * (travel_bit * 2);
+        g = ((k | (k / N)) & mask);
+        // Calculate the permuted Gray code by xor with the start point (e).
+        transgc[e][d][i] = (g ^ e);
+      }
+    } // d
+  } // e
+
+  // Count the consecutive '1' bits (trailing) on the right.
+  tsb1mod3[0] = 0;
+  for (i = 1; i < N; i++) {
+    v = ~i; // Count the 0s.
+    v = (v ^ (v - 1)) >> 1; // Set v's trailing 0s to 1s and zero rest
+    for (c = 0; v; c++) {
+      v >>= 1;
+    }
+    tsb1mod3[i] = c % n;
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// hilbert_sort3()    Sort points using the 3d Hilbert curve.                //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::hilbert_split(point* vertexarray,int arraysize,int gc0,int gc1,
+                              REAL bxmin, REAL bxmax, REAL bymin, REAL bymax, 
+                              REAL bzmin, REAL bzmax)
+{
+  point swapvert;
+  int axis, d;
+  REAL split;
+  int i, j;
+
+
+  // Find the current splitting axis. 'axis' is a value 0, or 1, or 2, which 
+  //   correspoding to x-, or y- or z-axis.
+  axis = (gc0 ^ gc1) >> 1; 
+
+  // Calulate the split position along the axis.
+  if (axis == 0) {
+    split = 0.5 * (bxmin + bxmax);
+  } else if (axis == 1) {
+    split = 0.5 * (bymin + bymax);
+  } else { // == 2
+    split = 0.5 * (bzmin + bzmax);
+  }
+
+  // Find the direction (+1 or -1) of the axis. If 'd' is +1, the direction
+  //   of the axis is to the positive of the axis, otherwise, it is -1.
+  d = ((gc0 & (1<<axis)) == 0) ? 1 : -1;
+
+
+  // Partition the vertices into left- and right-arrays such that left points
+  //   have Hilbert indices lower than the right points.
+  i = 0;
+  j = arraysize - 1;
+
+  // Partition the vertices into left- and right-arrays.
+  if (d > 0) {
+    do {
+      for (; i < arraysize; i++) {      
+        if (vertexarray[i][axis] >= split) break;
+      }
+      for (; j >= 0; j--) {
+        if (vertexarray[j][axis] < split) break;
+      }
+      // Is the partition finished?
+      if (i == (j + 1)) break;
+      // Swap i-th and j-th vertices.
+      swapvert = vertexarray[i];
+      vertexarray[i] = vertexarray[j];
+      vertexarray[j] = swapvert;
+      // Continue patitioning the array;
+    } while (true);
+  } else {
+    do {
+      for (; i < arraysize; i++) {      
+        if (vertexarray[i][axis] <= split) break;
+      }
+      for (; j >= 0; j--) {
+        if (vertexarray[j][axis] > split) break;
+      }
+      // Is the partition finished?
+      if (i == (j + 1)) break;
+      // Swap i-th and j-th vertices.
+      swapvert = vertexarray[i];
+      vertexarray[i] = vertexarray[j];
+      vertexarray[j] = swapvert;
+      // Continue patitioning the array;
+    } while (true);
+  }
+
+  return i;
+}
+
+void tetgenmesh::hilbert_sort3(point* vertexarray, int arraysize, int e, int d, 
+                               REAL bxmin, REAL bxmax, REAL bymin, REAL bymax, 
+                               REAL bzmin, REAL bzmax, int depth)
+{
+  REAL x1, x2, y1, y2, z1, z2;
+  int p[9], w, e_w, d_w, k, ei, di;
+  int n = 3, mask = 7;
+
+  p[0] = 0;
+  p[8] = arraysize;
+
+  // Sort the points according to the 1st order Hilbert curve in 3d.
+  p[4] = hilbert_split(vertexarray, p[8], transgc[e][d][3], transgc[e][d][4], 
+                       bxmin, bxmax, bymin, bymax, bzmin, bzmax);
+  p[2] = hilbert_split(vertexarray, p[4], transgc[e][d][1], transgc[e][d][2], 
+                       bxmin, bxmax, bymin, bymax, bzmin, bzmax);
+  p[1] = hilbert_split(vertexarray, p[2], transgc[e][d][0], transgc[e][d][1], 
+                       bxmin, bxmax, bymin, bymax, bzmin, bzmax);
+  p[3] = hilbert_split(&(vertexarray[p[2]]), p[4] - p[2], 
+                       transgc[e][d][2], transgc[e][d][3], 
+                       bxmin, bxmax, bymin, bymax, bzmin, bzmax) + p[2];
+  p[6] = hilbert_split(&(vertexarray[p[4]]), p[8] - p[4], 
+                       transgc[e][d][5], transgc[e][d][6], 
+                       bxmin, bxmax, bymin, bymax, bzmin, bzmax) + p[4];
+  p[5] = hilbert_split(&(vertexarray[p[4]]), p[6] - p[4], 
+                       transgc[e][d][4], transgc[e][d][5], 
+                       bxmin, bxmax, bymin, bymax, bzmin, bzmax) + p[4];
+  p[7] = hilbert_split(&(vertexarray[p[6]]), p[8] - p[6], 
+                       transgc[e][d][6], transgc[e][d][7], 
+                       bxmin, bxmax, bymin, bymax, bzmin, bzmax) + p[6];
+
+  if (b->hilbert_order > 0) {
+    // A maximum order is prescribed. 
+    if ((depth + 1) == b->hilbert_order) {
+      // The maximum prescribed order is reached.
+      return;
+    }
+  }
+
+  // Recursively sort the points in sub-boxes.
+  for (w = 0; w < 8; w++) {
+    // w is the local Hilbert index (NOT Gray code).
+    // Sort into the sub-box either there are more than 2 points in it, or
+    //   the prescribed order of the curve is not reached yet.
+    //if ((p[w+1] - p[w] > b->hilbert_limit) || (b->hilbert_order > 0)) {
+    if ((p[w+1] - p[w]) > b->hilbert_limit) {
+      // Calculcate the start point (ei) of the curve in this sub-box.
+      //   update e = e ^ (e(w) left_rotate (d+1)).
+      if (w == 0) {
+        e_w = 0;
+      } else {
+        //   calculate e(w) = gc(2 * floor((w - 1) / 2)).
+        k = 2 * ((w - 1) / 2); 
+        e_w = k ^ (k >> 1); // = gc(k).
+      }
+      k = e_w;
+      e_w = ((k << (d+1)) & mask) | ((k >> (n-d-1)) & mask);
+      ei = e ^ e_w;
+      // Calulcate the direction (di) of the curve in this sub-box.
+      //   update d = (d + d(w) + 1) % n
+      if (w == 0) {
+        d_w = 0;
+      } else {
+        d_w = ((w % 2) == 0) ? tsb1mod3[w - 1] : tsb1mod3[w];
+      }
+      di = (d + d_w + 1) % n;
+      // Calculate the bounding box of the sub-box.
+      if (transgc[e][d][w] & 1) { // x-axis
+        x1 = 0.5 * (bxmin + bxmax);
+        x2 = bxmax;
+      } else {
+        x1 = bxmin;
+        x2 = 0.5 * (bxmin + bxmax);
+      }
+      if (transgc[e][d][w] & 2) { // y-axis
+        y1 = 0.5 * (bymin + bymax);
+        y2 = bymax;
+      } else {
+        y1 = bymin;
+        y2 = 0.5 * (bymin + bymax);
+      }
+      if (transgc[e][d][w] & 4) { // z-axis
+        z1 = 0.5 * (bzmin + bzmax);
+        z2 = bzmax;
+      } else {
+        z1 = bzmin;
+        z2 = 0.5 * (bzmin + bzmax);
+      }
+      hilbert_sort3(&(vertexarray[p[w]]), p[w+1] - p[w], ei, di, 
+                    x1, x2, y1, y2, z1, z2, depth+1);
+    } // if (p[w+1] - p[w] > 1)
+  } // w
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// brio_multiscale_sort()    Sort the points using BRIO and Hilbert curve.   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::brio_multiscale_sort(point* vertexarray, int arraysize, 
+                                      int threshold, REAL ratio, int *depth)
+{
+  int middle;
+
+  middle = 0;
+  if (arraysize >= threshold) {
+    (*depth)++;
+    middle = arraysize * ratio;
+    brio_multiscale_sort(vertexarray, middle, threshold, ratio, depth);
+  }
+  // Sort the right-array (rnd-th round) using the Hilbert curve.
+  hilbert_sort3(&(vertexarray[middle]), arraysize - middle, 0, 0, // e, d
+                xmin, xmax, ymin, ymax, zmin, zmax, 0); // depth.
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// randomnation()    Generate a random number between 0 and 'choices' - 1.   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+unsigned long tetgenmesh::randomnation(unsigned int choices)
+{
+  unsigned long newrandom;
+
+  if (choices >= 714025l) {
+    newrandom = (randomseed * 1366l + 150889l) % 714025l;
+    randomseed = (newrandom * 1366l + 150889l) % 714025l;
+    newrandom = newrandom * (choices / 714025l) + randomseed;
+    if (newrandom >= choices) {
+      return newrandom - choices;
+    } else {
+      return newrandom;
+    }
+  } else {
+    randomseed = (randomseed * 1366l + 150889l) % 714025l;
+    return randomseed % choices;
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// randomsample()    Randomly sample the tetrahedra for point loation.       //
+//                                                                           //
+// Searching begins from one of handles:  the input 'searchtet', a recently  //
+// encountered tetrahedron 'recenttet',  or from one chosen from a random    //
+// sample.  The choice is made by determining which one's origin is closest  //
+// to the point we are searching for.                                        //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::randomsample(point searchpt,triface *searchtet)
+{
+  tetrahedron *firsttet, *tetptr;
+  point torg;
+  void **sampleblock;
+  uintptr_t alignptr;
+  long sampleblocks, samplesperblock, samplenum;
+  long tetblocks, i, j;
+  REAL searchdist, dist;
+
+  if (b->verbose > 2) {
+    printf("      Random sampling tetrahedra for searching point %d.\n",
+           pointmark(searchpt));
+  }
+
+  if (!nonconvex) {
+    if (searchtet->tet == NULL) {
+      // A null tet. Choose the recenttet as the starting tet.
+      *searchtet = recenttet;
+    }
+
+    // 'searchtet' should be a valid tetrahedron. Choose the base face
+    //   whose vertices must not be 'dummypoint'.
+    searchtet->ver = 3;
+    // Record the distance from its origin to the searching point.
+    torg = org(*searchtet);
+    searchdist = (searchpt[0] - torg[0]) * (searchpt[0] - torg[0]) +
+                 (searchpt[1] - torg[1]) * (searchpt[1] - torg[1]) +
+                 (searchpt[2] - torg[2]) * (searchpt[2] - torg[2]);
+
+    // If a recently encountered tetrahedron has been recorded and has not
+    //   been deallocated, test it as a good starting point.
+    if (recenttet.tet != searchtet->tet) {
+      recenttet.ver = 3;
+      torg = org(recenttet);
+      dist = (searchpt[0] - torg[0]) * (searchpt[0] - torg[0]) +
+             (searchpt[1] - torg[1]) * (searchpt[1] - torg[1]) +
+             (searchpt[2] - torg[2]) * (searchpt[2] - torg[2]);
+      if (dist < searchdist) {
+        *searchtet = recenttet;
+        searchdist = dist;
+      }
+    }
+  } else {
+    // The mesh is non-convex. Do not use 'recenttet'.
+    searchdist = longest;
+  }
+
+  // Select "good" candidate using k random samples, taking the closest one.
+  //   The number of random samples taken is proportional to the fourth root
+  //   of the number of tetrahedra in the mesh. 
+  while (samples * samples * samples * samples < tetrahedrons->items) {
+    samples++;
+  }
+  // Find how much blocks in current tet pool.
+  tetblocks = (tetrahedrons->maxitems + b->tetrahedraperblock - 1) 
+            / b->tetrahedraperblock;
+  // Find the average samples per block. Each block at least have 1 sample.
+  samplesperblock = 1 + (samples / tetblocks);
+  sampleblocks = samples / samplesperblock;
+  sampleblock = tetrahedrons->firstblock;
+  for (i = 0; i < sampleblocks; i++) {
+    alignptr = (uintptr_t) (sampleblock + 1);
+    firsttet = (tetrahedron *)
+               (alignptr + (uintptr_t) tetrahedrons->alignbytes
+               - (alignptr % (uintptr_t) tetrahedrons->alignbytes));
+    for (j = 0; j < samplesperblock; j++) {
+      if (i == tetblocks - 1) {
+        // This is the last block.
+        samplenum = randomnation((int)
+                      (tetrahedrons->maxitems - (i * b->tetrahedraperblock)));
+      } else {
+        samplenum = randomnation(b->tetrahedraperblock);
+      }
+      tetptr = (tetrahedron *)
+               (firsttet + (samplenum * tetrahedrons->itemwords));
+      torg = (point) tetptr[4];
+      if (torg != (point) NULL) {
+        dist = (searchpt[0] - torg[0]) * (searchpt[0] - torg[0]) +
+               (searchpt[1] - torg[1]) * (searchpt[1] - torg[1]) +
+               (searchpt[2] - torg[2]) * (searchpt[2] - torg[2]);
+        if (dist < searchdist) {
+          searchtet->tet = tetptr;
+          searchtet->ver = 11; // torg = org(t);
+          searchdist = dist;
+        }
+      } else {
+        // A dead tet. Re-sample it.
+        if (i != tetblocks - 1) j--;
+      }
+    }
+    sampleblock = (void **) *sampleblock;
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// locate()    Find a tetrahedron containing a given point.                  //
+//                                                                           //
+// Begins its search from 'searchtet', assume there is a line segment L from //
+// a vertex of 'searchtet' to the query point 'searchpt', and simply walk    //
+// towards 'searchpt' by traversing all faces intersected by L.              //
+//                                                                           //
+// On completion, 'searchtet' is a tetrahedron that contains 'searchpt'. The //
+// returned value indicates one of the following cases:                      //
+//   - ONVERTEX, the search point lies on the origin of 'searchtet'.         //
+//   - ONEDGE, the search point lies on an edge of 'searchtet'.              //
+//   - ONFACE, the search point lies on a face of 'searchtet'.               //
+//   - INTET, the search point lies in the interior of 'searchtet'.          //
+//   - OUTSIDE, the search point lies outside the mesh. 'searchtet' is a     //
+//              hull face which is visible by the search point.              //
+//                                                                           //
+// WARNING: This routine is designed for convex triangulations, and will not //
+// generally work after the holes and concavities have been carved.          //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+enum tetgenmesh::locateresult 
+  tetgenmesh::locate(point searchpt, triface* searchtet, int chkencflag)
+{
+  point torg, tdest, tapex, toppo;
+  enum {ORGMOVE, DESTMOVE, APEXMOVE} nextmove;
+  REAL ori, oriorg, oridest, oriapex;
+  enum locateresult loc = OUTSIDE;
+  int t1ver;
+  int s;
+
+  if (searchtet->tet == NULL) {
+    // A null tet. Choose the recenttet as the starting tet.
+    searchtet->tet = recenttet.tet;
+  }
+
+  // Check if we are in the outside of the convex hull.
+  if (ishulltet(*searchtet)) {
+    // Get its adjacent tet (inside the hull).
+    searchtet->ver = 3;
+    fsymself(*searchtet);
+  }
+
+  // Let searchtet be the face such that 'searchpt' lies above to it.
+  for (searchtet->ver = 0; searchtet->ver < 4; searchtet->ver++) {
+    torg = org(*searchtet);
+    tdest = dest(*searchtet);
+    tapex = apex(*searchtet);
+    ori = orient3d(torg, tdest, tapex, searchpt); 
+    if (ori < 0.0) break;
+  }
+  if (searchtet->ver == 4) {
+    terminatetetgen(this, 2);
+  }
+
+  // Walk through tetrahedra to locate the point.
+  while (true) {
+
+    toppo = oppo(*searchtet);
+    
+    // Check if the vertex is we seek.
+    if (toppo == searchpt) {
+      // Adjust the origin of searchtet to be searchpt.
+      esymself(*searchtet);
+      eprevself(*searchtet);
+      loc = ONVERTEX; // return ONVERTEX;
+      break;
+    }
+
+    // We enter from one of serarchtet's faces, which face do we exit?
+    oriorg = orient3d(tdest, tapex, toppo, searchpt); 
+    oridest = orient3d(tapex, torg, toppo, searchpt);
+    oriapex = orient3d(torg, tdest, toppo, searchpt);
+
+    // Now decide which face to move. It is possible there are more than one
+    //   faces are viable moves. If so, randomly choose one.
+    if (oriorg < 0) {
+      if (oridest < 0) {
+        if (oriapex < 0) {
+          // All three faces are possible.
+          s = randomnation(3); // 's' is in {0,1,2}.
+          if (s == 0) {
+            nextmove = ORGMOVE;
+          } else if (s == 1) {
+            nextmove = DESTMOVE;
+          } else {
+            nextmove = APEXMOVE;
+          }
+        } else {
+          // Two faces, opposite to origin and destination, are viable.
+          //s = randomnation(2); // 's' is in {0,1}.
+          if (randomnation(2)) {
+            nextmove = ORGMOVE;
+          } else {
+            nextmove = DESTMOVE;
+          }
+        }
+      } else {
+        if (oriapex < 0) {
+          // Two faces, opposite to origin and apex, are viable.
+          //s = randomnation(2); // 's' is in {0,1}.
+          if (randomnation(2)) {
+            nextmove = ORGMOVE;
+          } else {
+            nextmove = APEXMOVE;
+          }
+        } else {
+          // Only the face opposite to origin is viable.
+          nextmove = ORGMOVE;
+        }
+      }
+    } else {
+      if (oridest < 0) {
+        if (oriapex < 0) {
+          // Two faces, opposite to destination and apex, are viable.
+          //s = randomnation(2); // 's' is in {0,1}.
+          if (randomnation(2)) {
+            nextmove = DESTMOVE;
+          } else {
+            nextmove = APEXMOVE;
+          }
+        } else {
+          // Only the face opposite to destination is viable.
+          nextmove = DESTMOVE;
+        }
+      } else {
+        if (oriapex < 0) {
+          // Only the face opposite to apex is viable.
+          nextmove = APEXMOVE;
+        } else {
+          // The point we seek must be on the boundary of or inside this
+          //   tetrahedron. Check for boundary cases.
+          if (oriorg == 0) {
+            // Go to the face opposite to origin.
+            enextesymself(*searchtet);
+            if (oridest == 0) {
+              eprevself(*searchtet); // edge oppo->apex
+              if (oriapex == 0) {
+                // oppo is duplicated with p.
+                loc = ONVERTEX; // return ONVERTEX;
+                break;
+              }
+              loc = ONEDGE; // return ONEDGE;
+              break;
+            }
+            if (oriapex == 0) {
+              enextself(*searchtet); // edge dest->oppo
+              loc = ONEDGE; // return ONEDGE;
+              break;
+            }
+            loc = ONFACE; // return ONFACE;
+            break;
+          }
+          if (oridest == 0) {
+            // Go to the face opposite to destination.
+            eprevesymself(*searchtet);
+            if (oriapex == 0) {
+              eprevself(*searchtet); // edge oppo->org
+              loc = ONEDGE; // return ONEDGE;
+              break;
+            }
+            loc = ONFACE; // return ONFACE;
+            break;
+          }
+          if (oriapex == 0) {
+            // Go to the face opposite to apex
+            esymself(*searchtet);
+            loc = ONFACE; // return ONFACE;
+            break;
+          }
+          loc = INTETRAHEDRON; // return INTETRAHEDRON;
+          break;
+        }
+      }
+    }
+    
+    // Move to the selected face.
+    if (nextmove == ORGMOVE) {
+      enextesymself(*searchtet);
+    } else if (nextmove == DESTMOVE) {
+      eprevesymself(*searchtet);
+    } else {
+      esymself(*searchtet);
+    }
+    if (chkencflag) {
+      // Check if we are walking across a subface.
+      if (issubface(*searchtet)) {
+        loc = ENCSUBFACE;
+        break;
+      }
+    }
+    // Move to the adjacent tetrahedron (maybe a hull tetrahedron).
+    fsymself(*searchtet);
+    if (oppo(*searchtet) == dummypoint) {
+      loc = OUTSIDE; // return OUTSIDE;
+      break;
+    }
+
+    // Retreat the three vertices of the base face.
+    torg = org(*searchtet);
+    tdest = dest(*searchtet);
+    tapex = apex(*searchtet);
+
+  } // while (true)
+
+  return loc;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// flippush()    Push a face (possibly will be flipped) into flipstack.      //
+//                                                                           //
+// The face is marked. The flag is used to check the validity of the face on //
+// its popup.  Some other flips may change it already.                       //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::flippush(badface*& fstack, triface* flipface)
+{
+  if (!facemarked(*flipface)) {
+    badface *newflipface = (badface *) flippool->alloc();
+    newflipface->tt = *flipface;
+    markface(newflipface->tt);
+    // Push this face into stack.
+    newflipface->nextitem = fstack;
+    fstack = newflipface;
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// incrementalflip()    Incrementally flipping to construct DT.              //
+//                                                                           //
+// Faces need to be checked for flipping are already queued in 'flipstack'.  //
+// Return the total number of performed flips.                               //
+//                                                                           //
+// Comment:  This routine should be only used in the incremental Delaunay    //
+// construction.  In other cases, lawsonflip3d() should be used.             // 
+//                                                                           //
+// If the new point lies outside of the convex hull ('hullflag' is set). The //
+// incremental flip algorithm still works as usual.  However, we must ensure //
+// that every flip (2-to-3 or 3-to-2) does not create a duplicated (existing)//
+// edge or face. Otherwise, the underlying space of the triangulation becomes//
+// non-manifold and it is not possible to flip further.                      //
+// Thanks to Joerg Rambau and Frank Lutz for helping in this issue.          //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::incrementalflip(point newpt, int hullflag, flipconstraints *fc)
+{
+  badface *popface;
+  triface fliptets[5], *parytet;
+  point *pts, *parypt, pe;
+  REAL sign, ori;
+  int flipcount = 0;
+  int t1ver;
+  int i;
+
+  if (b->verbose > 2) {
+    printf("      Lawson flip (%ld faces).\n", flippool->items);
+  }
+
+  if (hullflag) {
+    // 'newpt' lies in the outside of the convex hull. 
+    // Mark all hull vertices which are connecting to it.
+    popface = flipstack;
+    while (popface != NULL) {
+      pts = (point *) popface->tt.tet;
+      for (i = 4; i < 8; i++) {
+        if ((pts[i] != newpt) && (pts[i] != dummypoint)) {
+          if (!pinfected(pts[i])) {
+            pinfect(pts[i]);
+            cavetetvertlist->newindex((void **) &parypt);
+            *parypt = pts[i];
+          }
+        } 
+      }
+      popface = popface->nextitem;
+    }
+  }
+
+  // Loop until the queue is empty.
+  while (flipstack != NULL) {
+
+    // Pop a face from the stack.
+    popface = flipstack;
+    fliptets[0] = popface->tt;
+    flipstack = flipstack->nextitem; // The next top item in stack.
+    flippool->dealloc((void *) popface);
+
+    // Skip it if it is a dead tet (destroyed by previous flips).
+    if (isdeadtet(fliptets[0])) continue;
+    // Skip it if it is not the same tet as we saved.
+    if (!facemarked(fliptets[0])) continue;
+
+    unmarkface(fliptets[0]);    
+
+    if ((point) fliptets[0].tet[7] == dummypoint) {
+      // It must be a hull edge.
+      fliptets[0].ver = epivot[fliptets[0].ver];
+      // A hull edge. The current convex hull may be enlarged.
+      fsym(fliptets[0], fliptets[1]);
+      pts = (point *) fliptets[1].tet;
+      ori = orient3d(pts[4], pts[5], pts[6], newpt);
+      if (ori < 0) {
+        // Visible. The convex hull will be enlarged.
+        // Decide which flip (2-to-3, 3-to-2, or 4-to-1) to use.
+        // Check if the tet [a,c,e,d] or [c,b,e,d] exists.
+        enext(fliptets[1], fliptets[2]); 
+        eprev(fliptets[1], fliptets[3]); 
+        fnextself(fliptets[2]); // [a,c,e,*]
+        fnextself(fliptets[3]); // [c,b,e,*]
+        if (oppo(fliptets[2]) == newpt) {
+          if (oppo(fliptets[3]) == newpt) {
+            // Both tets exist! A 4-to-1 flip is found.
+            terminatetetgen(this, 2); // Report a bug.
+          } else {
+            esym(fliptets[2], fliptets[0]);
+            fnext(fliptets[0], fliptets[1]); 
+            fnext(fliptets[1], fliptets[2]); 
+            // Perform a 3-to-2 flip. Replace edge [c,a] by face [d,e,b].
+            // This corresponds to my standard labels, where edge [e,d] is
+            //   repalced by face [a,b,c], and a is the new vertex. 
+            //   [0] [c,a,d,e] (d = newpt)
+            //   [1] [c,a,e,b] (c = dummypoint)
+            //   [2] [c,a,b,d]
+            flip32(fliptets, 1, fc);
+          }
+        } else {
+          if (oppo(fliptets[3]) == newpt) {
+            fnext(fliptets[3], fliptets[0]);
+            fnext(fliptets[0], fliptets[1]); 
+            fnext(fliptets[1], fliptets[2]); 
+            // Perform a 3-to-2 flip. Replace edge [c,b] by face [d,a,e].
+            //   [0] [c,b,d,a] (d = newpt)
+            //   [1] [c,b,a,e] (c = dummypoint)
+            //   [2] [c,b,e,d]
+            flip32(fliptets, 1, fc);
+          } else {
+            if (hullflag) {
+              // Reject this flip if pe is already marked.
+              pe = oppo(fliptets[1]);
+              if (!pinfected(pe)) {
+                pinfect(pe);
+                cavetetvertlist->newindex((void **) &parypt);
+                *parypt = pe;
+                // Perform a 2-to-3 flip.
+                flip23(fliptets, 1, fc);
+              } else {
+                // Reject this flip.
+                flipcount--;
+              }
+            } else {
+              // Perform a 2-to-3 flip. Replace face [a,b,c] by edge [e,d].
+              //   [0] [a,b,c,d], d = newpt.
+              //   [1] [b,a,c,e], c = dummypoint.
+              flip23(fliptets, 1, fc);
+            }
+          }
+        }
+        flipcount++;
+      } 
+      continue;
+    } // if (dummypoint)
+
+    fsym(fliptets[0], fliptets[1]);
+    if ((point) fliptets[1].tet[7] == dummypoint) {
+      // A hull face is locally Delaunay.
+      continue;
+    }
+    // Check if the adjacent tet has already been tested.
+    if (marktested(fliptets[1])) {
+      // It has been tested and it is Delaunay.
+      continue;
+    }
+
+    // Test whether the face is locally Delaunay or not.
+    pts = (point *) fliptets[1].tet; 
+    if (b->weighted) {
+      sign = orient4d_s(pts[4], pts[5], pts[6], pts[7], newpt,
+                        pts[4][3], pts[5][3], pts[6][3], pts[7][3],
+                        newpt[3]);
+    } else {
+      sign = insphere_s(pts[4], pts[5], pts[6], pts[7], newpt);
+    }
+
+
+    if (sign < 0) {
+      point pd = newpt;
+      point pe = oppo(fliptets[1]);
+      // Check the convexity of its three edges. Stop checking either a
+      //   locally non-convex edge (ori < 0) or a flat edge (ori = 0) is
+      //   encountered, and 'fliptet' represents that edge.
+      for (i = 0; i < 3; i++) {
+        ori = orient3d(org(fliptets[0]), dest(fliptets[0]), pd, pe);
+        if (ori <= 0) break;
+        enextself(fliptets[0]);
+      }
+      if (ori > 0) {
+        // A 2-to-3 flip is found.
+        //   [0] [a,b,c,d], 
+        //   [1] [b,a,c,e]. no dummypoint.
+        flip23(fliptets, 0, fc);
+        flipcount++;
+      } else { // ori <= 0
+        // The edge ('fliptets[0]' = [a',b',c',d]) is non-convex or flat,
+        //   where the edge [a',b'] is one of [a,b], [b,c], and [c,a].
+        // Check if there are three or four tets sharing at this edge.        
+        esymself(fliptets[0]); // [b,a,d,c]
+        for (i = 0; i < 3; i++) {
+          fnext(fliptets[i], fliptets[i+1]);
+        }
+        if (fliptets[3].tet == fliptets[0].tet) {
+          // A 3-to-2 flip is found. (No hull tet.)
+          flip32(fliptets, 0, fc); 
+          flipcount++;
+        } else {
+          // There are more than 3 tets at this edge.
+          fnext(fliptets[3], fliptets[4]);
+          if (fliptets[4].tet == fliptets[0].tet) {
+            if (ori == 0) {
+              // A 4-to-4 flip is found. (Two hull tets may be involved.)
+              // Current tets in 'fliptets':
+              //   [0] [b,a,d,c] (d may be newpt)
+              //   [1] [b,a,c,e]
+              //   [2] [b,a,e,f] (f may be dummypoint)
+              //   [3] [b,a,f,d]
+              esymself(fliptets[0]); // [a,b,c,d] 
+              // A 2-to-3 flip replaces face [a,b,c] by edge [e,d].
+              //   This creates a degenerate tet [e,d,a,b] (tmpfliptets[0]).
+              //   It will be removed by the followed 3-to-2 flip.
+              flip23(fliptets, 0, fc); // No hull tet.
+              fnext(fliptets[3], fliptets[1]);
+              fnext(fliptets[1], fliptets[2]);
+              // Current tets in 'fliptets':
+              //   [0] [...]
+              //   [1] [b,a,d,e] (degenerated, d may be new point).
+              //   [2] [b,a,e,f] (f may be dummypoint)
+              //   [3] [b,a,f,d]
+              // A 3-to-2 flip replaces edge [b,a] by face [d,e,f].
+              //   Hull tets may be involved (f may be dummypoint).
+              flip32(&(fliptets[1]), (apex(fliptets[3]) == dummypoint), fc);
+              flipcount++;
+            }
+          }
+        }
+      } // ori
+    } else {
+      // The adjacent tet is Delaunay. Mark it to avoid testing it again.
+      marktest(fliptets[1]);
+      // Save it for unmarking it later.
+      cavebdrylist->newindex((void **) &parytet);
+      *parytet = fliptets[1];
+    }
+
+  } // while (flipstack)
+
+  // Unmark saved tetrahedra.
+  for (i = 0; i < cavebdrylist->objects; i++) {
+    parytet = (triface *) fastlookup(cavebdrylist, i);
+    unmarktest(*parytet);
+  }
+  cavebdrylist->restart();
+
+  if (hullflag) {
+    // Unmark infected vertices.
+    for (i = 0; i < cavetetvertlist->objects; i++) {
+      parypt = (point *) fastlookup(cavetetvertlist, i);
+      puninfect(*parypt);
+    }
+    cavetetvertlist->restart();
+  }
+
+
+  return flipcount;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// initialdelaunay()    Create an initial Delaunay tetrahedralization.       //
+//                                                                           //
+// The tetrahedralization contains only one tetrahedron abcd, and four hull  //
+// tetrahedra. The points pa, pb, pc, and pd must be linearly independent.   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::initialdelaunay(point pa, point pb, point pc, point pd)
+{
+  triface firsttet, tetopa, tetopb, tetopc, tetopd;
+  triface worktet, worktet1;
+
+  if (b->verbose > 2) {
+    printf("      Create init tet (%d, %d, %d, %d)\n", pointmark(pa),
+           pointmark(pb), pointmark(pc), pointmark(pd));
+  }
+
+  // Create the first tetrahedron.
+  maketetrahedron(&firsttet);
+  setvertices(firsttet, pa, pb, pc, pd);
+  // Create four hull tetrahedra.
+  maketetrahedron(&tetopa);
+  setvertices(tetopa, pb, pc, pd, dummypoint);
+  maketetrahedron(&tetopb);
+  setvertices(tetopb, pc, pa, pd, dummypoint);
+  maketetrahedron(&tetopc);
+  setvertices(tetopc, pa, pb, pd, dummypoint);
+  maketetrahedron(&tetopd);
+  setvertices(tetopd, pb, pa, pc, dummypoint);
+  hullsize += 4;
+
+  // Connect hull tetrahedra to firsttet (at four faces of firsttet).
+  bond(firsttet, tetopd);
+  esym(firsttet, worktet);
+  bond(worktet, tetopc); // ab
+  enextesym(firsttet, worktet);
+  bond(worktet, tetopa); // bc 
+  eprevesym(firsttet, worktet);
+  bond(worktet, tetopb); // ca
+
+  // Connect hull tetrahedra together (at six edges of firsttet).
+  esym(tetopc, worktet); 
+  esym(tetopd, worktet1);
+  bond(worktet, worktet1); // ab
+  esym(tetopa, worktet);
+  eprevesym(tetopd, worktet1);
+  bond(worktet, worktet1); // bc
+  esym(tetopb, worktet);
+  enextesym(tetopd, worktet1);
+  bond(worktet, worktet1); // ca
+  eprevesym(tetopc, worktet);
+  enextesym(tetopb, worktet1);
+  bond(worktet, worktet1); // da
+  eprevesym(tetopa, worktet);
+  enextesym(tetopc, worktet1);
+  bond(worktet, worktet1); // db
+  eprevesym(tetopb, worktet);
+  enextesym(tetopa, worktet1);
+  bond(worktet, worktet1); // dc
+
+  // Set the vertex type.
+  if (pointtype(pa) == UNUSEDVERTEX) {
+    setpointtype(pa, VOLVERTEX);
+  }
+  if (pointtype(pb) == UNUSEDVERTEX) {
+    setpointtype(pb, VOLVERTEX);
+  }
+  if (pointtype(pc) == UNUSEDVERTEX) {
+    setpointtype(pc, VOLVERTEX);
+  }
+  if (pointtype(pd) == UNUSEDVERTEX) {
+    setpointtype(pd, VOLVERTEX);
+  }
+
+  setpoint2tet(pa, encode(firsttet));
+  setpoint2tet(pb, encode(firsttet));
+  setpoint2tet(pc, encode(firsttet));
+  setpoint2tet(pd, encode(firsttet));
+
+  // Remember the first tetrahedron.
+  recenttet = firsttet;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// incrementaldelaunay()    Create a Delaunay tetrahedralization by          //
+//                          the incremental approach.                        //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+
+void tetgenmesh::incrementaldelaunay(clock_t& tv)
+{
+  triface searchtet;
+  point *permutarray, swapvertex;
+  REAL v1[3], v2[3], n[3];
+  REAL bboxsize, bboxsize2, bboxsize3, ori;
+  int randindex; 
+  int ngroup = 0;
+  int i, j;
+
+  if (!b->quiet) {
+    printf("Delaunizing vertices...\n");
+  }
+
+  // Form a random permuation (uniformly at random) of the set of vertices.
+  permutarray = new point[in->numberofpoints];
+  points->traversalinit();
+
+  if (b->no_sort) {
+    if (b->verbose) {
+      printf("  Using the input order.\n"); 
+    }
+    for (i = 0; i < in->numberofpoints; i++) {
+      permutarray[i] = (point) points->traverse();
+    }
+  } else {
+    if (b->verbose) {
+      printf("  Permuting vertices.\n"); 
+    }
+    srand(in->numberofpoints);
+    for (i = 0; i < in->numberofpoints; i++) {
+      randindex = rand() % (i + 1); // randomnation(i + 1);
+      permutarray[i] = permutarray[randindex];
+      permutarray[randindex] = (point) points->traverse();
+    }
+    if (b->brio_hilbert) { // -b option
+      if (b->verbose) {
+        printf("  Sorting vertices.\n"); 
+      }
+      hilbert_init(in->mesh_dim);
+      brio_multiscale_sort(permutarray, in->numberofpoints, b->brio_threshold, 
+                           b->brio_ratio, &ngroup);
+    }
+  }
+
+  tv = clock(); // Remember the time for sorting points.
+
+  // Calculate the diagonal size of its bounding box.
+  bboxsize = sqrt(norm2(xmax - xmin, ymax - ymin, zmax - zmin));
+  bboxsize2 = bboxsize * bboxsize;
+  bboxsize3 = bboxsize2 * bboxsize;
+
+  // Make sure the second vertex is not identical with the first one.
+  i = 1;
+  while ((distance(permutarray[0],permutarray[i])/bboxsize)<b->epsilon) {
+    i++;
+    if (i == in->numberofpoints - 1) {
+      printf("Exception:  All vertices are (nearly) identical (Tol = %g).\n",
+             b->epsilon);
+      terminatetetgen(this, 10);
+    }
+  }
+  if (i > 1) {
+    // Swap to move the non-identical vertex from index i to index 1.
+    swapvertex = permutarray[i];
+    permutarray[i] = permutarray[1];
+    permutarray[1] = swapvertex;
+  }
+
+  // Make sure the third vertex is not collinear with the first two.
+  // Acknowledgement:  Thanks Jan Pomplun for his correction by using 
+  //   epsilon^2 and epsilon^3 (instead of epsilon). 2013-08-15.
+  i = 2;
+  for (j = 0; j < 3; j++) {
+    v1[j] = permutarray[1][j] - permutarray[0][j];
+    v2[j] = permutarray[i][j] - permutarray[0][j];
+  }
+  cross(v1, v2, n);
+  while ((sqrt(norm2(n[0], n[1], n[2])) / bboxsize2) < 
+         (b->epsilon * b->epsilon)) {
+    i++;
+    if (i == in->numberofpoints - 1) {
+      printf("Exception:  All vertices are (nearly) collinear (Tol = %g).\n",
+             b->epsilon);
+      terminatetetgen(this, 10);
+    }
+    for (j = 0; j < 3; j++) {
+      v2[j] = permutarray[i][j] - permutarray[0][j];
+    }
+    cross(v1, v2, n);
+  }
+  if (i > 2) {
+    // Swap to move the non-identical vertex from index i to index 1.
+    swapvertex = permutarray[i];
+    permutarray[i] = permutarray[2];
+    permutarray[2] = swapvertex;
+  }
+
+  // Make sure the fourth vertex is not coplanar with the first three.
+  i = 3;
+  ori = orient3dfast(permutarray[0], permutarray[1], permutarray[2], 
+                     permutarray[i]);
+  while ((fabs(ori) / bboxsize3) < (b->epsilon * b->epsilon * b->epsilon)) {
+    i++;
+    if (i == in->numberofpoints) {
+      printf("Exception:  All vertices are coplanar (Tol = %g).\n",
+             b->epsilon);
+      terminatetetgen(this, 10);
+    }
+    ori = orient3dfast(permutarray[0], permutarray[1], permutarray[2], 
+                       permutarray[i]);
+  }
+  if (i > 3) {
+    // Swap to move the non-identical vertex from index i to index 1.
+    swapvertex = permutarray[i];
+    permutarray[i] = permutarray[3];
+    permutarray[3] = swapvertex;
+  }
+
+  // Orient the first four vertices in permutarray so that they follow the
+  //   right-hand rule.
+  if (ori > 0.0) {
+    // Swap the first two vertices.
+    swapvertex = permutarray[0];
+    permutarray[0] = permutarray[1];
+    permutarray[1] = swapvertex;
+  }
+
+  // Create the initial Delaunay tetrahedralization.
+  initialdelaunay(permutarray[0], permutarray[1], permutarray[2],
+                  permutarray[3]);
+
+  if (b->verbose) {
+    printf("  Incrementally inserting vertices.\n");
+  }
+  insertvertexflags ivf;
+  flipconstraints fc;
+
+  // Choose algorithm: Bowyer-Watson (default) or Incremental Flip
+  if (b->incrflip) {
+    ivf.bowywat = 0;
+    ivf.lawson = 1;
+    fc.enqflag = 1;
+  } else {
+    ivf.bowywat = 1;
+    ivf.lawson = 0;
+  }
+
+
+  for (i = 4; i < in->numberofpoints; i++) {
+    if (pointtype(permutarray[i]) == UNUSEDVERTEX) {
+      setpointtype(permutarray[i], VOLVERTEX);
+    }
+    if (b->brio_hilbert || b->no_sort) { // -b or -b/1
+      // Start the last updated tet.
+      searchtet.tet = recenttet.tet;
+    } else { // -b0
+      // Randomly choose the starting tet for point location.
+      searchtet.tet = NULL;
+    }
+    ivf.iloc = (int) OUTSIDE;
+    // Insert the vertex.
+    if (insertpoint(permutarray[i], &searchtet, NULL, NULL, &ivf)) {
+      if (flipstack != NULL) {
+        // Perform flip to recover Delaunayness.
+        incrementalflip(permutarray[i], (ivf.iloc == (int) OUTSIDE), &fc);
+      }
+    } else {
+      if (ivf.iloc == (int) ONVERTEX) {
+        // The point already exists. Mark it and do nothing on it.
+        swapvertex = org(searchtet);
+        if (b->object != tetgenbehavior::STL) {
+          if (!b->quiet) {
+            printf("Warning:  Point #%d is coincident with #%d. Ignored!\n",
+                   pointmark(permutarray[i]), pointmark(swapvertex));
+          }
+        }
+        setpoint2ppt(permutarray[i], swapvertex);
+        setpointtype(permutarray[i], DUPLICATEDVERTEX);
+        dupverts++;
+      } else if (ivf.iloc == (int) NEARVERTEX) {
+        swapvertex = org(searchtet);
+        if (!b->quiet) {
+          printf("Warning:  Point %d is replaced by point %d.\n",
+                 pointmark(permutarray[i]), pointmark(swapvertex));
+          printf("  Avoid creating a very short edge (len = %g) (< %g).\n",
+                 permutarray[i][3], minedgelength);
+          printf("  You may try a smaller tolerance (-T) (current is %g)\n", 
+                 b->epsilon);
+          printf("  or use the option -M0/1 to avoid such replacement.\n");
+        }
+        // Remember it is a duplicated point.
+        setpoint2ppt(permutarray[i], swapvertex);
+        setpointtype(permutarray[i], DUPLICATEDVERTEX);
+        dupverts++;
+      } else if (ivf.iloc == (int) NONREGULAR) {
+        // The point is non-regular. Skipped.
+        if (b->verbose) {
+          printf("  Point #%d is non-regular, skipped.\n",
+                 pointmark(permutarray[i]));
+        }
+        setpointtype(permutarray[i], NREGULARVERTEX);
+        nonregularcount++;
+      }
+    }
+  }
+
+
+
+  delete [] permutarray;
+}
+
+////                                                                       ////
+////                                                                       ////
+//// delaunay_cxx /////////////////////////////////////////////////////////////
+
+//// surface_cxx //////////////////////////////////////////////////////////////
+////                                                                       ////
+////                                                                       ////
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// flipshpush()    Push a facet edge into flip stack.                        //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::flipshpush(face* flipedge)
+{
+  badface *newflipface;
+
+  newflipface = (badface *) flippool->alloc();
+  newflipface->ss = *flipedge;
+  newflipface->forg = sorg(*flipedge);
+  newflipface->fdest = sdest(*flipedge);
+  newflipface->nextitem = flipstack;
+  flipstack = newflipface;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// flip22()    Perform a 2-to-2 flip in surface mesh.                        //
+//                                                                           //
+// 'flipfaces' is an array of two subfaces. On input, they are [a,b,c] and   //
+// [b,a,d]. On output, they are [c,d,b] and [d,c,a]. As a result, edge [a,b] //
+// is replaced by edge [c,d].                                                //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::flip22(face* flipfaces, int flipflag, int chkencflag)
+{
+  face bdedges[4], outfaces[4], infaces[4];
+  face bdsegs[4];
+  face checkface;
+  point pa, pb, pc, pd;
+  int i;
+
+  pa = sorg(flipfaces[0]);
+  pb = sdest(flipfaces[0]);
+  pc = sapex(flipfaces[0]);
+  pd = sapex(flipfaces[1]);
+
+  if (sorg(flipfaces[1]) != pb) {
+    sesymself(flipfaces[1]);
+  }
+
+  flip22count++;
+
+  // Collect the four boundary edges.
+  senext(flipfaces[0], bdedges[0]);
+  senext2(flipfaces[0], bdedges[1]);
+  senext(flipfaces[1], bdedges[2]);
+  senext2(flipfaces[1], bdedges[3]);
+
+  // Collect outer boundary faces.
+  for (i = 0; i < 4; i++) {
+    spivot(bdedges[i], outfaces[i]);
+    infaces[i] = outfaces[i];
+    sspivot(bdedges[i], bdsegs[i]);
+    if (outfaces[i].sh != NULL) {
+      if (isshsubseg(bdedges[i])) {
+        spivot(infaces[i], checkface);
+        while (checkface.sh != bdedges[i].sh) {
+          infaces[i] = checkface;
+          spivot(infaces[i], checkface);
+        }
+      }
+    }
+  }
+
+  // The flags set in these two subfaces do not change.
+  // Shellmark does not change.
+  // area constraint does not change.
+
+  // Transform [a,b,c] -> [c,d,b].
+  setshvertices(flipfaces[0], pc, pd, pb);
+  // Transform [b,a,d] -> [d,c,a].
+  setshvertices(flipfaces[1], pd, pc, pa);
+
+  // Update the point-to-subface map.
+  if (pointtype(pa) == FREEFACETVERTEX) {
+    setpoint2sh(pa, sencode(flipfaces[1]));
+  }
+  if (pointtype(pb) == FREEFACETVERTEX) {
+    setpoint2sh(pb, sencode(flipfaces[0]));
+  }
+  if (pointtype(pc) == FREEFACETVERTEX) {
+    setpoint2sh(pc, sencode(flipfaces[0]));
+  }
+  if (pointtype(pd) == FREEFACETVERTEX) {
+    setpoint2sh(pd, sencode(flipfaces[0]));
+  }
+
+  // Reconnect boundary edges to outer boundary faces.
+  for (i = 0; i < 4; i++) {
+    if (outfaces[(3 + i) % 4].sh != NULL) {
+      // Make sure that the subface has the ori as the segment.
+      if (bdsegs[(3 + i) % 4].sh != NULL) {
+        bdsegs[(3 + i) % 4].shver = 0;
+        if (sorg(bdedges[i]) != sorg(bdsegs[(3 + i) % 4])) {
+          sesymself(bdedges[i]);
+        }
+      }
+      sbond1(bdedges[i], outfaces[(3 + i) % 4]);
+      sbond1(infaces[(3 + i) % 4], bdedges[i]);
+    } else {
+      sdissolve(bdedges[i]);
+    }
+    if (bdsegs[(3 + i) % 4].sh != NULL) {
+      ssbond(bdedges[i], bdsegs[(3 + i) % 4]);
+      if (chkencflag & 1) {
+        // Queue this segment for encroaching check.
+        enqueuesubface(badsubsegs, &(bdsegs[(3 + i) % 4]));
+      }
+    } else {
+      ssdissolve(bdedges[i]);
+    }
+  }
+
+  if (chkencflag & 2) {
+    // Queue the flipped subfaces for quality/encroaching checks.
+    for (i = 0; i < 2; i++) {
+      enqueuesubface(badsubfacs, &(flipfaces[i]));
+    }
+  }
+
+  recentsh = flipfaces[0];
+
+  if (flipflag) {
+    // Put the boundary edges into flip stack.
+    for (i = 0; i < 4; i++) {
+      flipshpush(&(bdedges[i]));
+    }
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// flip31()    Remove a vertex by transforming 3-to-1 subfaces.              //
+//                                                                           //
+// 'flipfaces' is an array of subfaces. Its length is at least 4.  On input, //
+// the first three faces are: [p,a,b], [p,b,c], and [p,c,a]. This routine    //
+// replaces them by one face [a,b,c], it is returned in flipfaces[3].        //
+//                                                                           //
+// NOTE: The three old subfaces are not deleted within this routine.  They   //
+// still hold pointers to their adjacent subfaces. These informations are    //
+// needed by the routine 'sremovevertex()' for recovering a segment.         //
+// The caller of this routine must delete the old subfaces after their uses. //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::flip31(face* flipfaces, int flipflag)
+{
+  face bdedges[3], outfaces[3], infaces[3];
+  face bdsegs[3];
+  face checkface;
+  point pa, pb, pc;
+  int i;
+
+  pa = sdest(flipfaces[0]);
+  pb = sdest(flipfaces[1]);
+  pc = sdest(flipfaces[2]);
+
+  flip31count++;
+
+  // Collect all infos at the three boundary edges.
+  for (i = 0; i < 3; i++) {
+    senext(flipfaces[i], bdedges[i]);
+    spivot(bdedges[i], outfaces[i]);
+    infaces[i] = outfaces[i];
+    sspivot(bdedges[i], bdsegs[i]);
+    if (outfaces[i].sh != NULL) {
+      if (isshsubseg(bdedges[i])) {
+        spivot(infaces[i], checkface);
+        while (checkface.sh != bdedges[i].sh) {
+          infaces[i] = checkface;
+          spivot(infaces[i], checkface);
+        }
+      }
+    }
+  } // i
+
+  // Create a new subface.
+  makeshellface(subfaces, &(flipfaces[3]));
+  setshvertices(flipfaces[3], pa, pb,pc);
+  setshellmark(flipfaces[3], shellmark(flipfaces[0]));
+  if (checkconstraints) {
+    //area = areabound(flipfaces[0]);
+    setareabound(flipfaces[3], areabound(flipfaces[0]));
+  }
+  if (useinsertradius) {
+    setfacetindex(flipfaces[3], getfacetindex(flipfaces[0]));
+  }
+
+  // Update the point-to-subface map.
+  if (pointtype(pa) == FREEFACETVERTEX) {
+    setpoint2sh(pa, sencode(flipfaces[3]));
+  }
+  if (pointtype(pb) == FREEFACETVERTEX) {
+    setpoint2sh(pb, sencode(flipfaces[3]));
+  }
+  if (pointtype(pc) == FREEFACETVERTEX) {
+    setpoint2sh(pc, sencode(flipfaces[3]));
+  }
+
+  // Update the three new boundary edges.
+  bdedges[0] = flipfaces[3];         // [a,b]
+  senext(flipfaces[3], bdedges[1]);  // [b,c]
+  senext2(flipfaces[3], bdedges[2]); // [c,a]
+
+  // Reconnect boundary edges to outer boundary faces.
+  for (i = 0; i < 3; i++) {
+    if (outfaces[i].sh != NULL) {
+      // Make sure that the subface has the ori as the segment.
+      if (bdsegs[i].sh != NULL) {
+        bdsegs[i].shver = 0;
+        if (sorg(bdedges[i]) != sorg(bdsegs[i])) {
+          sesymself(bdedges[i]);
+        }
+      }
+      sbond1(bdedges[i], outfaces[i]);
+      sbond1(infaces[i], bdedges[i]);
+    }
+    if (bdsegs[i].sh != NULL) {
+      ssbond(bdedges[i], bdsegs[i]);
+    }
+  }
+
+  recentsh = flipfaces[3];
+
+  if (flipflag) {
+    // Put the boundary edges into flip stack.
+    for (i = 0; i < 3; i++) {
+      flipshpush(&(bdedges[i]));
+    }
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// lawsonflip()    Flip non-locally Delaunay edges.                          //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+long tetgenmesh::lawsonflip()
+{
+  badface *popface;
+  face flipfaces[2];
+  point pa, pb, pc, pd;
+  REAL sign;
+  long flipcount = 0;
+
+  if (b->verbose > 2) {
+    printf("      Lawson flip %ld edges.\n", flippool->items);
+  }
+
+  while (flipstack != (badface *) NULL) {
+
+    // Pop an edge from the stack.
+    popface = flipstack;
+    flipfaces[0] = popface->ss;
+    pa = popface->forg;
+    pb = popface->fdest;
+    flipstack = popface->nextitem; // The next top item in stack.
+    flippool->dealloc((void *) popface);
+
+    // Skip it if it is dead.
+    if (flipfaces[0].sh[3] == NULL) continue;
+    // Skip it if it is not the same edge as we saved.
+    if ((sorg(flipfaces[0]) != pa) || (sdest(flipfaces[0]) != pb)) continue;
+    // Skip it if it is a subsegment.
+    if (isshsubseg(flipfaces[0])) continue;
+
+    // Get the adjacent face.
+    spivot(flipfaces[0], flipfaces[1]);
+    if (flipfaces[1].sh == NULL) continue; // Skip a hull edge.
+    pc = sapex(flipfaces[0]);
+    pd = sapex(flipfaces[1]);
+
+    sign = incircle3d(pa, pb, pc, pd);
+
+    if (sign < 0) {
+      // It is non-locally Delaunay. Flip it.
+      flip22(flipfaces, 1, 0);
+      flipcount++;
+    }
+  }
+
+  if (b->verbose > 2) {
+    printf("      Performed %ld flips.\n", flipcount);
+  }
+
+  return flipcount;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// sinsertvertex()    Insert a vertex into a triangulation of a facet.       //
+//                                                                           //
+// This function uses three global arrays: 'caveshlist', 'caveshbdlist', and //
+// 'caveshseglist'. On return, 'caveshlist' contains old subfaces in C(p),   //
+// 'caveshbdlist' contains new subfaces in C(p). If the new point lies on a  //
+// segment, 'cavesegshlist' returns the two new subsegments.                 //
+//                                                                           //
+// 'iloc' suggests the location of the point. If it is OUTSIDE, this routine //
+// will first locate the point. It starts searching from 'searchsh' or 'rec- //
+// entsh' if 'searchsh' is NULL.                                             //
+//                                                                           //
+// If 'bowywat' is set (1), the Bowyer-Watson algorithm is used to insert    //
+// the vertex. Otherwise, only insert the vertex in the initial cavity.      // 
+//                                                                           //
+// If 'iloc' is 'INSTAR', this means the cavity of this vertex was already   //
+// provided in the list 'caveshlist'.                                        //
+//                                                                           //
+// If 'splitseg' is not NULL, the new vertex lies on the segment and it will //
+// be split. 'iloc' must be either 'ONEDGE' or 'INSTAR'.                     //
+//                                                                           //
+// 'rflag' (rounding) is a parameter passed to slocate() function.  If it is //
+// set, after the location of the point is found, either ONEDGE or ONFACE,   //
+// round the result using an epsilon.                                        //
+//                                                                           //
+// NOTE: the old subfaces in C(p) are not deleted. They're needed in case we //
+// want to remove the new point immediately.                                 //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::sinsertvertex(point insertpt, face *searchsh, face *splitseg,
+                              int iloc, int bowywat, int rflag)
+{
+  face cavesh, neighsh, *parysh;
+  face newsh, casout, casin;
+  face checkseg;
+  point pa, pb;
+  enum locateresult loc = OUTSIDE;
+  REAL sign, ori;
+  int i, j;
+
+  if (b->verbose > 2) {
+    printf("      Insert facet point %d.\n", pointmark(insertpt));
+  }
+
+  if (bowywat == 3) {
+    loc = INSTAR;
+  }
+
+  if ((splitseg != NULL) && (splitseg->sh != NULL)) {
+    // A segment is going to be split, no point location.
+    spivot(*splitseg, *searchsh);
+    if (loc != INSTAR) loc = ONEDGE;
+  } else {
+    if (loc != INSTAR) loc = (enum locateresult) iloc;
+    if (loc == OUTSIDE) {
+      // Do point location in surface mesh.
+      if (searchsh->sh == NULL) {
+        *searchsh = recentsh;
+      }
+      // Search the vertex. An above point must be provided ('aflag' = 1).
+      loc = slocate(insertpt, searchsh, 1, 1, rflag);
+    }
+  }
+
+
+  // Form the initial sC(p).
+  if (loc == ONFACE) {
+    // Add the face into list (in B-W cavity).
+    smarktest(*searchsh);
+    caveshlist->newindex((void **) &parysh);
+    *parysh = *searchsh;
+  } else if (loc == ONEDGE) {
+    if ((splitseg != NULL) && (splitseg->sh != NULL)) {
+      splitseg->shver = 0;
+      pa = sorg(*splitseg);
+    } else {
+      pa = sorg(*searchsh);
+    }
+    if (searchsh->sh != NULL) {
+      // Collect all subfaces share at this edge.
+      neighsh = *searchsh;
+      while (1) {
+        // Adjust the origin of its edge to be 'pa'.
+        if (sorg(neighsh) != pa) sesymself(neighsh);
+        // Add this face into list (in B-W cavity).
+        smarktest(neighsh);
+        caveshlist->newindex((void **) &parysh);
+        *parysh = neighsh;
+        // Add this face into face-at-splitedge list.
+        cavesegshlist->newindex((void **) &parysh);
+        *parysh = neighsh;
+        // Go to the next face at the edge.
+        spivotself(neighsh);
+        // Stop if all faces at the edge have been visited.
+        if (neighsh.sh == searchsh->sh) break;
+        if (neighsh.sh == NULL) break;
+      }
+    } // If (not a non-dangling segment).
+  } else if (loc == ONVERTEX) {
+    return (int) loc;
+  } else if (loc == OUTSIDE) {
+    // Comment: This should only happen during the surface meshing step.
+    // Enlarge the convex hull of the triangulation by including p.
+    // An above point of the facet is set in 'dummypoint' to replace
+    // orient2d tests by orient3d tests.
+    // Imagine that the current edge a->b (in 'searchsh') is horizontal in a
+    //   plane, and a->b is directed from left to right, p lies above a->b.  
+    //   Find the right-most edge of the triangulation which is visible by p.
+    neighsh = *searchsh;
+    while (1) {
+      senext2self(neighsh);
+      spivot(neighsh, casout);
+      if (casout.sh == NULL) {
+        // A convex hull edge. Is it visible by p.
+        ori = orient3d(sorg(neighsh), sdest(neighsh), dummypoint, insertpt);
+        if (ori < 0) {
+          *searchsh = neighsh; // Visible, update 'searchsh'.
+        } else {
+          break; // 'searchsh' is the right-most visible edge.
+        }
+      } else {
+        if (sorg(casout) != sdest(neighsh)) sesymself(casout);
+        neighsh = casout;
+      }
+    }
+    // Create new triangles for all visible edges of p (from right to left).
+    casin.sh = NULL;  // No adjacent face at right.
+    pa = sorg(*searchsh);
+    pb = sdest(*searchsh);
+    while (1) {
+      // Create a new subface on top of the (visible) edge.
+      makeshellface(subfaces, &newsh); 
+      setshvertices(newsh, pb, pa, insertpt);
+      setshellmark(newsh, shellmark(*searchsh));
+      if (checkconstraints) {
+        //area = areabound(*searchsh);
+        setareabound(newsh, areabound(*searchsh));
+      }
+      if (useinsertradius) {
+        setfacetindex(newsh, getfacetindex(*searchsh));
+      }
+      // Connect the new subface to the bottom subfaces.
+      sbond1(newsh, *searchsh);
+      sbond1(*searchsh, newsh);
+      // Connect the new subface to its right-adjacent subface.
+      if (casin.sh != NULL) {
+        senext(newsh, casout);
+        sbond1(casout, casin);
+        sbond1(casin, casout);
+      }
+      // The left-adjacent subface has not been created yet.
+      senext2(newsh, casin);
+      // Add the new face into list (inside the B-W cavity).
+      smarktest(newsh);
+      caveshlist->newindex((void **) &parysh);
+      *parysh = newsh;
+      // Move to the convex hull edge at the left of 'searchsh'.
+      neighsh = *searchsh;
+      while (1) {
+        senextself(neighsh);
+        spivot(neighsh, casout);
+        if (casout.sh == NULL) {
+          *searchsh = neighsh;
+          break;
+        }
+        if (sorg(casout) != sdest(neighsh)) sesymself(casout);
+        neighsh = casout;
+      }
+      // A convex hull edge. Is it visible by p.
+      pa = sorg(*searchsh);
+      pb = sdest(*searchsh);
+      ori = orient3d(pa, pb, dummypoint, insertpt);
+      // Finish the process if p is not visible by the hull edge.
+      if (ori >= 0) break;
+    }
+  } else if (loc == INSTAR) {
+    // Under this case, the sub-cavity sC(p) has already been formed in
+    //   insertvertex().
+  }
+
+  // Form the Bowyer-Watson cavity sC(p).
+  for (i = 0; i < caveshlist->objects; i++) {
+    cavesh = * (face *) fastlookup(caveshlist, i);
+    for (j = 0; j < 3; j++) {
+      if (!isshsubseg(cavesh)) {
+        spivot(cavesh, neighsh);
+        if (neighsh.sh != NULL) {
+          // The adjacent face exists.
+          if (!smarktested(neighsh)) {
+            if (bowywat) {
+              if (loc == INSTAR) { // if (bowywat > 2) {
+                // It must be a boundary edge.
+                sign = 1;
+              } else {
+                // Check if this subface is connected to adjacent tet(s).
+                if (!isshtet(neighsh)) {
+                  // Check if the subface is non-Delaunay wrt. the new pt.
+                  sign = incircle3d(sorg(neighsh), sdest(neighsh), 
+                                    sapex(neighsh), insertpt);
+                } else {
+                  // It is connected to an adjacent tet. A boundary edge.
+                  sign = 1;
+                }
+              }
+              if (sign < 0) {
+                // Add the adjacent face in list (in B-W cavity).
+                smarktest(neighsh);
+                caveshlist->newindex((void **) &parysh);
+                *parysh = neighsh;
+              }
+            } else {
+              sign = 1; // A boundary edge.
+            }
+          } else {
+            sign = -1; // Not a boundary edge.
+          }
+        } else {
+          // No adjacent face. It is a hull edge.
+          if (loc == OUTSIDE) {
+            // It is a boundary edge if it does not contain p.
+            if ((sorg(cavesh) == insertpt) || (sdest(cavesh) == insertpt)) {
+              sign = -1; // Not a boundary edge.
+            } else {
+              sign = 1; // A boundary edge.
+            }
+          } else {
+            sign = 1; // A boundary edge.
+          }
+        }
+      } else {
+        // Do not across a segment. It is a boundary edge.
+        sign = 1;
+      }
+      if (sign >= 0) {
+        // Add a boundary edge.
+        caveshbdlist->newindex((void **) &parysh);
+        *parysh = cavesh;
+      }
+      senextself(cavesh);
+    } // j
+  } // i
+
+
+  // Creating new subfaces.
+  for (i = 0; i < caveshbdlist->objects; i++) {
+    parysh = (face *) fastlookup(caveshbdlist, i);
+    sspivot(*parysh, checkseg);
+    if ((parysh->shver & 01) != 0) sesymself(*parysh);
+    pa = sorg(*parysh);
+    pb = sdest(*parysh);
+    // Create a new subface.
+    makeshellface(subfaces, &newsh); 
+    setshvertices(newsh, pa, pb, insertpt);
+    setshellmark(newsh, shellmark(*parysh));
+    if (checkconstraints) {
+      //area = areabound(*parysh);
+      setareabound(newsh, areabound(*parysh));
+    }
+    if (useinsertradius) {
+      setfacetindex(newsh, getfacetindex(*parysh));
+    }
+    // Update the point-to-subface map.
+    if (pointtype(pa) == FREEFACETVERTEX) {
+      setpoint2sh(pa, sencode(newsh));
+    }
+    if (pointtype(pb) == FREEFACETVERTEX) {
+      setpoint2sh(pb, sencode(newsh));
+    }
+    // Connect newsh to outer subfaces.
+    spivot(*parysh, casout);
+    if (casout.sh != NULL) {
+      casin = casout;
+      if (checkseg.sh != NULL) {
+        // Make sure that newsh has the right ori at this segment.
+        checkseg.shver = 0;
+        if (sorg(newsh) != sorg(checkseg)) {
+          sesymself(newsh);
+          sesymself(*parysh); // This side should also be inverse.
+        }
+        spivot(casin, neighsh);
+        while (neighsh.sh != parysh->sh) {
+          casin = neighsh;
+          spivot(casin, neighsh);
+        }
+      }
+      sbond1(newsh, casout);
+      sbond1(casin, newsh);
+    }
+    if (checkseg.sh != NULL) {
+      ssbond(newsh, checkseg);
+    }
+    // Connect oldsh <== newsh (for connecting adjacent new subfaces).
+    //   *parysh and newsh point to the same edge and the same ori.
+    sbond1(*parysh, newsh);
+  }
+
+  if (newsh.sh != NULL) {
+    // Set a handle for searching.
+    recentsh = newsh;
+  }
+
+  // Update the point-to-subface map.
+  if (pointtype(insertpt) == FREEFACETVERTEX) {
+    setpoint2sh(insertpt, sencode(newsh));
+  }
+
+  // Connect adjacent new subfaces together.
+  for (i = 0; i < caveshbdlist->objects; i++) {
+    // Get an old subface at edge [a, b].
+    parysh = (face *) fastlookup(caveshbdlist, i);
+    spivot(*parysh, newsh); // The new subface [a, b, p].
+    senextself(newsh); // At edge [b, p].
+    spivot(newsh, neighsh);
+    if (neighsh.sh == NULL) {
+      // Find the adjacent new subface at edge [b, p].
+      pb = sdest(*parysh);
+      neighsh = *parysh;
+      while (1) {
+        senextself(neighsh);
+        spivotself(neighsh);
+        if (neighsh.sh == NULL) break;
+        if (!smarktested(neighsh)) break;
+        if (sdest(neighsh) != pb) sesymself(neighsh);
+      }
+      if (neighsh.sh != NULL) {
+        // Now 'neighsh' is a new subface at edge [b, #].
+        if (sorg(neighsh) != pb) sesymself(neighsh);
+        senext2self(neighsh); // Go to the open edge [p, b].
+        sbond(newsh, neighsh);
+      }
+    }
+    spivot(*parysh, newsh); // The new subface [a, b, p].
+    senext2self(newsh); // At edge [p, a].
+    spivot(newsh, neighsh);
+    if (neighsh.sh == NULL) {
+      // Find the adjacent new subface at edge [p, a].
+      pa = sorg(*parysh);
+      neighsh = *parysh;
+      while (1) {
+        senext2self(neighsh);
+        spivotself(neighsh);
+        if (neighsh.sh == NULL) break;
+        if (!smarktested(neighsh)) break;
+        if (sorg(neighsh) != pa) sesymself(neighsh);
+      }
+      if (neighsh.sh != NULL) {
+        // Now 'neighsh' is a new subface at edge [#, a].
+        if (sdest(neighsh) != pa) sesymself(neighsh);
+        senextself(neighsh); // Go to the open edge [a, p].
+        sbond(newsh, neighsh);
+      }
+    }
+  }
+
+  if ((loc == ONEDGE) || ((splitseg != NULL) && (splitseg->sh != NULL))
+      || (cavesegshlist->objects > 0l)) {
+    // An edge is being split. We distinguish two cases:
+    //   (1) the edge is not on the boundary of the cavity;
+    //   (2) the edge is on the boundary of the cavity.
+    // In case (2), the edge is either a segment or a hull edge. There are
+    //   degenerated new faces in the cavity. They must be removed.
+    face aseg, bseg, aoutseg, boutseg;
+
+    for (i = 0; i < cavesegshlist->objects; i++) {
+      // Get the saved old subface.
+      parysh = (face *) fastlookup(cavesegshlist, i);
+      // Get a possible new degenerated subface.
+      spivot(*parysh, cavesh);
+      if (sapex(cavesh) == insertpt) {
+        // Found a degenerated new subface, i.e., case (2).
+        if (cavesegshlist->objects > 1) {
+          // There are more than one subface share at this edge.
+          j = (i + 1) % (int) cavesegshlist->objects;
+          parysh = (face *) fastlookup(cavesegshlist, j);
+          spivot(*parysh, neighsh);
+          // Adjust cavesh and neighsh both at edge a->b, and has p as apex.
+          if (sorg(neighsh) != sorg(cavesh)) {
+            sesymself(neighsh);
+          }
+          // Connect adjacent faces at two other edges of cavesh and neighsh.
+          //   As a result, the two degenerated new faces are squeezed from the
+          //   new triangulation of the cavity. Note that the squeezed faces
+          //   still hold the adjacent informations which will be used in 
+          //   re-connecting subsegments (if they exist). 
+          for (j = 0; j < 2; j++) { 
+            senextself(cavesh);
+            senextself(neighsh);
+            spivot(cavesh, newsh);
+            spivot(neighsh, casout);
+            sbond1(newsh, casout); // newsh <- casout.
+          }
+        } else {
+          // There is only one subface containing this edge [a,b]. Squeeze the
+          //   degenerated new face [a,b,c] by disconnecting it from its two 
+          //   adjacent subfaces at edges [b,c] and [c,a]. Note that the face
+          //   [a,b,c] still hold the connection to them.
+          for (j = 0; j < 2; j++) {
+            senextself(cavesh);
+            spivot(cavesh, newsh);
+            sdissolve(newsh);
+          }
+        }
+        //recentsh = newsh;
+        // Update the point-to-subface map.
+        if (pointtype(insertpt) == FREEFACETVERTEX) {
+          setpoint2sh(insertpt, sencode(newsh));
+        }
+      }
+    }
+
+    if ((splitseg != NULL) && (splitseg->sh != NULL)) {
+      if (loc != INSTAR) { // if (bowywat < 3) {
+        smarktest(*splitseg); // Mark it as being processed.
+      }
+      
+      aseg = *splitseg;
+      pa = sorg(*splitseg);
+      pb = sdest(*splitseg);
+
+      // Insert the new point p.
+      makeshellface(subsegs, &aseg);
+      makeshellface(subsegs, &bseg);
+
+      setshvertices(aseg, pa, insertpt, NULL);
+      setshvertices(bseg, insertpt, pb, NULL);
+      setshellmark(aseg, shellmark(*splitseg));
+      setshellmark(bseg, shellmark(*splitseg));
+      if (checkconstraints) {
+        setareabound(aseg, areabound(*splitseg));
+        setareabound(bseg, areabound(*splitseg));
+      }
+      if (useinsertradius) {
+        setfacetindex(aseg, getfacetindex(*splitseg));
+        setfacetindex(bseg, getfacetindex(*splitseg));
+      }
+
+      // Connect [#, a]<->[a, p].
+      senext2(*splitseg, boutseg); // Temporarily use boutseg.
+      spivotself(boutseg);
+      if (boutseg.sh != NULL) {
+        senext2(aseg, aoutseg);
+        sbond(boutseg, aoutseg);
+      }
+      // Connect [p, b]<->[b, #].
+      senext(*splitseg, aoutseg);
+      spivotself(aoutseg);
+      if (aoutseg.sh != NULL) {
+        senext(bseg, boutseg);
+        sbond(boutseg, aoutseg);
+      }
+      // Connect [a, p] <-> [p, b].
+      senext(aseg, aoutseg);
+      senext2(bseg, boutseg);
+      sbond(aoutseg, boutseg);
+
+      // Connect subsegs [a, p] and [p, b] to adjacent new subfaces.
+      // Although the degenerated new faces have been squeezed. They still
+      //   hold the connections to the actual new faces. 
+      for (i = 0; i < cavesegshlist->objects; i++) {        
+        parysh = (face *) fastlookup(cavesegshlist, i);
+        spivot(*parysh, neighsh);
+        // neighsh is a degenerated new face.
+        if (sorg(neighsh) != pa) {
+          sesymself(neighsh);
+        }
+        senext2(neighsh, newsh);
+        spivotself(newsh); // The edge [p, a] in newsh
+        ssbond(newsh, aseg);
+        senext(neighsh, newsh);
+        spivotself(newsh); // The edge [b, p] in newsh
+        ssbond(newsh, bseg);
+      }
+
+
+      // Let the point remember the segment it lies on.
+      if (pointtype(insertpt) == FREESEGVERTEX) {
+        setpoint2sh(insertpt, sencode(aseg));
+      }
+      // Update the point-to-seg map.
+      if (pointtype(pa) == FREESEGVERTEX) {
+        setpoint2sh(pa, sencode(aseg));
+      }
+      if (pointtype(pb) == FREESEGVERTEX) {
+        setpoint2sh(pb, sencode(bseg));
+      }
+    } // if ((splitseg != NULL) && (splitseg->sh != NULL)) 
+
+    // Delete all degenerated new faces.
+    for (i = 0; i < cavesegshlist->objects; i++) {
+      parysh = (face *) fastlookup(cavesegshlist, i);
+      spivotself(*parysh);
+      if (sapex(*parysh) == insertpt) {
+        shellfacedealloc(subfaces, parysh->sh);
+      }
+    }
+    cavesegshlist->restart();
+
+    if ((splitseg != NULL) && (splitseg->sh != NULL)) {
+      // Return the two new subsegments (for further process).
+      //   Re-use 'cavesegshlist'.
+      cavesegshlist->newindex((void **) &parysh);
+      *parysh = aseg;
+      cavesegshlist->newindex((void **) &parysh);
+      *parysh = bseg;
+    }
+  } // if (loc == ONEDGE)
+
+
+  return (int) loc;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// sremovevertex()    Remove a vertex from the surface mesh.                 //
+//                                                                           //
+// 'delpt' (p) is the vertex to be removed. If 'parentseg' is not NULL, p is //
+// a segment vertex, and the origin of 'parentseg' is p. Otherwise, p is a   //
+// facet vertex, and the origin of 'parentsh' is p.                          //
+//                                                                           //
+// Within each facet, we first use a sequence of 2-to-2 flips to flip any    //
+// edge at p, finally use a 3-to-1 flip to remove p.                         //
+//                                                                           //
+// All new created subfaces are returned in the global array 'caveshbdlist'. //
+// The new segment (when p is on segment) is returned in 'parentseg'.        //
+//                                                                           //
+// If 'lawson' > 0, the Lawson flip algorithm is used to recover Delaunay-   //
+// ness after p is removed.                                                  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::sremovevertex(point delpt, face* parentsh, face* parentseg,
+                              int lawson)
+{
+  face flipfaces[4], spinsh, *parysh;
+  point pa, pb, pc, pd;
+  REAL ori1, ori2;
+  int it, i, j;
+
+  if (parentseg != NULL) {
+    // 'delpt' (p) should be a Steiner point inserted in a segment [a,b],
+    //   where 'parentseg' should be [p,b]. Find the segment [a,p].
+    face startsh, neighsh, nextsh;
+    face abseg, prevseg, checkseg;
+    face adjseg1, adjseg2;
+    face fakesh;
+    senext2(*parentseg, prevseg);
+    spivotself(prevseg);
+    prevseg.shver = 0;
+    // Restore the original segment [a,b].
+    pa = sorg(prevseg);
+    pb = sdest(*parentseg);
+    if (b->verbose > 2) {
+      printf("      Remove vertex %d from segment [%d, %d].\n", 
+             pointmark(delpt), pointmark(pa), pointmark(pb));
+    }
+    makeshellface(subsegs, &abseg);
+    setshvertices(abseg, pa, pb, NULL);
+    setshellmark(abseg, shellmark(*parentseg));
+    if (checkconstraints) {
+      setareabound(abseg, areabound(*parentseg));
+    }
+    if (useinsertradius) {
+      setfacetindex(abseg, getfacetindex(*parentseg));
+    }
+    // Connect [#, a]<->[a, b].
+    senext2(prevseg, adjseg1);
+    spivotself(adjseg1);
+    if (adjseg1.sh != NULL) {
+      adjseg1.shver = 0;
+      senextself(adjseg1);
+      senext2(abseg, adjseg2);
+      sbond(adjseg1, adjseg2);
+    }
+    // Connect [a, b]<->[b, #].
+    senext(*parentseg, adjseg1);
+    spivotself(adjseg1);
+    if (adjseg1.sh != NULL) {
+      adjseg1.shver = 0;
+      senext2self(adjseg1);
+      senext(abseg, adjseg2);
+      sbond(adjseg1, adjseg2);
+    }
+    // Update the point-to-segment map.
+    setpoint2sh(pa, sencode(abseg));
+    setpoint2sh(pb, sencode(abseg));
+
+    // Get the faces in face ring at segment [p, b].
+    //   Re-use array 'caveshlist'.
+    spivot(*parentseg, *parentsh);
+    if (parentsh->sh != NULL) {
+      spinsh = *parentsh;
+      while (1) {
+        // Save this face in list.
+        caveshlist->newindex((void **) &parysh);
+        *parysh = spinsh;
+        // Go to the next face in the ring.
+        spivotself(spinsh);
+        if (spinsh.sh == NULL) {
+          break; // It is possible there is only one facet.
+        }
+        if (spinsh.sh == parentsh->sh) break;
+      }
+    }
+
+    // Create the face ring of the new segment [a,b]. Each face in the ring
+    //   is [a,b,p] (degenerated!). It will be removed (automatically).
+    for (i = 0; i < caveshlist->objects; i++) {
+      parysh = (face *) fastlookup(caveshlist, i);
+      startsh = *parysh;
+      if (sorg(startsh) != delpt) {
+        sesymself(startsh);
+      }      
+      // startsh is [p, b, #1], find the subface [a, p, #2].
+      neighsh = startsh;
+      while (1) {
+        senext2self(neighsh);
+        sspivot(neighsh, checkseg);
+        if (checkseg.sh != NULL) {
+          // It must be the segment [a, p].
+          break;
+        }
+        spivotself(neighsh);
+        if (sorg(neighsh) != delpt) sesymself(neighsh);
+      }
+      // Now neighsh is [a, p, #2].
+      if (neighsh.sh != startsh.sh) {
+        // Detach the two subsegments [a,p] and [p,b] from subfaces.
+        ssdissolve(startsh);
+        ssdissolve(neighsh);
+        // Create a degenerated subface [a,b,p]. It is used to: (1) hold the
+        //   new segment [a,b]; (2) connect to the two adjacent subfaces
+        //   [p,b,#] and [a,p,#].
+        makeshellface(subfaces, &fakesh);
+        setshvertices(fakesh, pa, pb, delpt);
+        setshellmark(fakesh, shellmark(startsh));
+        // Connect fakesh to the segment [a,b].
+        ssbond(fakesh, abseg);
+        // Connect fakesh to adjacent subfaces: [p,b,#1] and [a,p,#2].
+        senext(fakesh, nextsh);
+        sbond(nextsh, startsh);
+        senext2(fakesh, nextsh);
+        sbond(nextsh, neighsh);
+        smarktest(fakesh); // Mark it as faked.
+      } else {
+        // Special case. There exists already a degenerated face [a,b,p]!
+        //   There is no need to create a faked subface here.
+        senext2self(neighsh); // [a,b,p]
+        // Since we will re-connect the face ring using the faked subfaces.
+        //   We put the adjacent face of [a,b,p] to the list.
+        spivot(neighsh, startsh); // The original adjacent subface.
+        if (sorg(startsh) != pa) sesymself(startsh);
+        sdissolve(startsh);
+        // Connect fakesh to the segment [a,b].
+        ssbond(startsh, abseg);
+        fakesh = startsh; // Do not mark it!
+        // Delete the degenerated subface.
+        shellfacedealloc(subfaces, neighsh.sh);
+      }
+      // Save the fakesh in list (for re-creating the face ring).
+      cavesegshlist->newindex((void **) &parysh);
+      *parysh = fakesh;
+    } // i
+    caveshlist->restart();
+
+    // Re-create the face ring.
+    if (cavesegshlist->objects > 1) {
+      for (i = 0; i < cavesegshlist->objects; i++) {
+        parysh = (face *) fastlookup(cavesegshlist, i);
+        fakesh = *parysh;
+        // Get the next face in the ring.
+        j = (i + 1) % cavesegshlist->objects;
+        parysh = (face *) fastlookup(cavesegshlist, j);
+        nextsh = *parysh;
+        sbond1(fakesh, nextsh);
+      }
+    }
+
+    // Delete the two subsegments containing p.
+    shellfacedealloc(subsegs, parentseg->sh);
+    shellfacedealloc(subsegs, prevseg.sh);
+    // Return the new segment.
+    *parentseg = abseg;
+  } else {
+    // p is inside the surface.
+    if (b->verbose > 2) {
+      printf("      Remove vertex %d from surface.\n", pointmark(delpt));
+    }
+    // Let 'delpt' be its apex.
+    senextself(*parentsh);
+    // For unifying the code, we add parentsh to list.
+    cavesegshlist->newindex((void **) &parysh);
+    *parysh = *parentsh;
+  }
+
+  // Remove the point (p).
+
+  for (it = 0; it < cavesegshlist->objects; it++) {
+    parentsh = (face *) fastlookup(cavesegshlist, it); // [a,b,p]
+    senextself(*parentsh); // [b,p,a].
+    spivotself(*parentsh);
+    if (sorg(*parentsh) != delpt) sesymself(*parentsh);
+    // now parentsh is [p,b,#].
+    if (sorg(*parentsh) != delpt) {
+      // The vertex has already been removed in above special case.
+      continue;
+    }
+
+    while (1) {      
+      // Initialize the flip edge list. Re-use 'caveshlist'.
+      spinsh = *parentsh; // [p, b, #]
+      while (1) {
+        caveshlist->newindex((void **) &parysh);
+        *parysh = spinsh;
+        senext2self(spinsh);
+        spivotself(spinsh);
+        if (spinsh.sh == parentsh->sh) break;
+        if (sorg(spinsh) != delpt) sesymself(spinsh);
+      } // while (1)
+
+      if (caveshlist->objects == 3) {
+        // Delete the point by a 3-to-1 flip.
+        for (i = 0; i < 3; i++) {
+          parysh = (face *) fastlookup(caveshlist, i);
+          flipfaces[i] = *parysh;
+        }
+        flip31(flipfaces, lawson);
+        for (i = 0; i < 3; i++) { 
+          shellfacedealloc(subfaces, flipfaces[i].sh);
+        }
+        caveshlist->restart();
+        // Save the new subface.
+        caveshbdlist->newindex((void **) &parysh);
+        *parysh = flipfaces[3];
+        // The vertex is removed.
+        break;
+      }
+
+      // Search an edge to flip.
+      for (i = 0; i < caveshlist->objects; i++) {
+        parysh = (face *) fastlookup(caveshlist, i);
+        flipfaces[0] = *parysh;
+        spivot(flipfaces[0], flipfaces[1]);
+        if (sorg(flipfaces[0]) != sdest(flipfaces[1])) 
+          sesymself(flipfaces[1]);
+        // Skip this edge if it belongs to a faked subface.
+        if (!smarktested(flipfaces[0]) && !smarktested(flipfaces[1])) {
+          pa = sorg(flipfaces[0]);
+          pb = sdest(flipfaces[0]);
+          pc = sapex(flipfaces[0]);
+          pd = sapex(flipfaces[1]);
+          calculateabovepoint4(pa, pb, pc, pd);
+          // Check if a 2-to-2 flip is possible.
+          ori1 = orient3d(pc, pd, dummypoint, pa);
+          ori2 = orient3d(pc, pd, dummypoint, pb);
+          if (ori1 * ori2 < 0) {
+            // A 2-to-2 flip is found.
+            flip22(flipfaces, lawson, 0);
+            // The i-th edge is flipped. The i-th and (i-1)-th subfaces are
+            //   changed. The 'flipfaces[1]' contains p as its apex.
+            senext2(flipfaces[1], *parentsh);
+            // Save the new subface.
+            caveshbdlist->newindex((void **) &parysh);
+            *parysh = flipfaces[0];
+            break;
+          }
+        } //
+      } // i
+
+      if (i == caveshlist->objects) {
+        // Do a flip22 and a flip31 to remove p.
+        parysh = (face *) fastlookup(caveshlist, 0);
+        flipfaces[0] = *parysh;
+        spivot(flipfaces[0], flipfaces[1]);
+        if (sorg(flipfaces[0]) != sdest(flipfaces[1])) {
+          sesymself(flipfaces[1]);
+        }
+        flip22(flipfaces, lawson, 0);
+        senext2(flipfaces[1], *parentsh);
+        // Save the new subface.
+        caveshbdlist->newindex((void **) &parysh);
+        *parysh = flipfaces[0];
+      }
+
+      // The edge list at p are changed.
+      caveshlist->restart();
+    } // while (1)
+
+  } // it
+
+  cavesegshlist->restart();
+
+  if (b->verbose > 2) {
+    printf("      Created %ld new subfaces.\n", caveshbdlist->objects);
+  }
+
+
+  if (lawson) {
+    lawsonflip();
+  }
+
+  return 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// slocate()    Locate a point in a surface triangulation.                   //
+//                                                                           //
+// Staring the search from 'searchsh'(it should not be NULL). Perform a line //
+// walk search for a subface containing the point (p).                       //
+//                                                                           //
+// If 'aflag' is set, the 'dummypoint' is pre-calculated so that it lies     //
+// above the 'searchsh' in its current orientation. The test if c is CCW to  //
+// the line a->b can be done by the test if c is below the oriented plane    //
+// a->b->dummypoint.                                                         //
+//                                                                           //
+// If 'cflag' is not TRUE, the triangulation may not be convex.  Stop search //
+// when a segment is met and return OUTSIDE.                                 //
+//                                                                           //
+// If 'rflag' (rounding) is set, after the location of the point is found,   //
+// either ONEDGE or ONFACE, round the result using an epsilon.               //
+//                                                                           //
+// The returned value indicates the following cases:                         //
+//   - ONVERTEX, p is the origin of 'searchsh'.                              //
+//   - ONEDGE, p lies on the edge of 'searchsh'.                             //
+//   - ONFACE, p lies in the interior of 'searchsh'.                         //
+//   - OUTSIDE, p lies outside of the triangulation, p is on the left-hand   //
+//     side of the edge 'searchsh'(s), i.e., org(s), dest(s), p are CW.      //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+enum tetgenmesh::locateresult tetgenmesh::slocate(point searchpt, 
+  face* searchsh, int aflag, int cflag, int rflag)
+{
+  face neighsh;
+  point pa, pb, pc;
+  enum locateresult loc;
+  enum {MOVE_BC, MOVE_CA} nextmove;
+  REAL ori, ori_bc, ori_ca;
+  int i;
+
+  pa = sorg(*searchsh);
+  pb = sdest(*searchsh);
+  pc = sapex(*searchsh);
+
+  if (!aflag) {
+    // No above point is given. Calculate an above point for this facet.
+    calculateabovepoint4(pa, pb, pc, searchpt);
+  }
+
+  // 'dummypoint' is given. Make sure it is above [a,b,c]
+  ori = orient3d(pa, pb, pc, dummypoint);
+  if (ori > 0) {
+    sesymself(*searchsh); // Reverse the face orientation.
+  } else if (ori == 0.0) {
+    // This case should not happen theoretically. But... 
+    return UNKNOWN; 
+  }
+
+  // Find an edge of the face s.t. p lies on its right-hand side (CCW).
+  for (i = 0; i < 3; i++) {
+    pa = sorg(*searchsh);
+    pb = sdest(*searchsh);
+    ori = orient3d(pa, pb, dummypoint, searchpt);
+    if (ori > 0) break;
+    senextself(*searchsh);
+  }
+  if (i == 3) {
+    return UNKNOWN;
+  }
+
+  pc = sapex(*searchsh);
+
+  if (pc == searchpt) {
+    senext2self(*searchsh);
+    return ONVERTEX;
+  }
+
+  while (1) {
+
+    ori_bc = orient3d(pb, pc, dummypoint, searchpt);
+    ori_ca = orient3d(pc, pa, dummypoint, searchpt);
+
+    if (ori_bc < 0) {
+      if (ori_ca < 0) { // (--)
+        // Any of the edges is a viable move.
+        if (randomnation(2)) {
+          nextmove = MOVE_CA;
+        } else {
+          nextmove = MOVE_BC;
+        }
+      } else { // (-#)
+        // Edge [b, c] is viable.
+        nextmove = MOVE_BC;
+      }
+    } else {
+      if (ori_ca < 0) { // (#-)
+        // Edge [c, a] is viable.
+        nextmove = MOVE_CA;
+      } else {
+        if (ori_bc > 0) {
+          if (ori_ca > 0) { // (++)
+            loc = ONFACE;  // Inside [a, b, c].
+            break;
+          } else { // (+0)
+            senext2self(*searchsh); // On edge [c, a].
+            loc = ONEDGE;
+            break;
+          }
+        } else { // ori_bc == 0
+          if (ori_ca > 0) { // (0+)
+            senextself(*searchsh); // On edge [b, c].
+            loc = ONEDGE;
+            break;
+          } else { // (00)
+            // p is coincident with vertex c. 
+            senext2self(*searchsh);
+            return ONVERTEX;
+          }
+        }
+      }
+    }
+
+    // Move to the next face.
+    if (nextmove == MOVE_BC) {
+      senextself(*searchsh);
+    } else {
+      senext2self(*searchsh);
+    }
+    if (!cflag) {
+      // NON-convex case. Check if we will cross a boundary.
+      if (isshsubseg(*searchsh)) {
+        return ENCSEGMENT;
+      }
+    }
+    spivot(*searchsh, neighsh);
+    if (neighsh.sh == NULL) {
+      return OUTSIDE; // A hull edge.
+    }
+    // Adjust the edge orientation.
+    if (sorg(neighsh) != sdest(*searchsh)) {
+      sesymself(neighsh);
+    }
+
+    // Update the newly discovered face and its endpoints.
+    *searchsh = neighsh;
+    pa = sorg(*searchsh);
+    pb = sdest(*searchsh);
+    pc = sapex(*searchsh);
+
+    if (pc == searchpt) {
+      senext2self(*searchsh);
+      return ONVERTEX;
+    }
+
+  } // while (1)
+
+  // assert(loc == ONFACE || loc == ONEDGE);
+
+
+  if (rflag) {
+    // Round the locate result before return.
+    REAL n[3], area_abc, area_abp, area_bcp, area_cap;
+
+    pa = sorg(*searchsh);
+    pb = sdest(*searchsh);
+    pc = sapex(*searchsh);
+
+    facenormal(pa, pb, pc, n, 1, NULL);
+    area_abc = sqrt(dot(n, n));
+
+    facenormal(pb, pc, searchpt, n, 1, NULL);
+    area_bcp = sqrt(dot(n, n));
+    if ((area_bcp / area_abc) < b->epsilon) {
+      area_bcp = 0; // Rounding.
+    }
+
+    facenormal(pc, pa, searchpt, n, 1, NULL);
+    area_cap = sqrt(dot(n, n));
+    if ((area_cap / area_abc) < b->epsilon) {
+      area_cap = 0; // Rounding
+    }
+
+    if ((loc == ONFACE) || (loc == OUTSIDE)) {
+      facenormal(pa, pb, searchpt, n, 1, NULL);
+      area_abp = sqrt(dot(n, n));
+      if ((area_abp / area_abc) < b->epsilon) {
+        area_abp = 0; // Rounding
+      }
+    } else { // loc == ONEDGE
+      area_abp = 0;
+    }
+
+    if (area_abp == 0) {
+      if (area_bcp == 0) {
+        senextself(*searchsh); 
+        loc = ONVERTEX; // p is close to b.
+      } else {
+        if (area_cap == 0) {
+          loc = ONVERTEX; // p is close to a.
+        } else {
+          loc = ONEDGE; // p is on edge [a,b].
+        }
+      }
+    } else if (area_bcp == 0) {
+      if (area_cap == 0) {
+        senext2self(*searchsh); 
+        loc = ONVERTEX; // p is close to c.
+      } else {
+        senextself(*searchsh);
+        loc = ONEDGE; // p is on edge [b,c].
+      }
+    } else if (area_cap == 0) {
+      senext2self(*searchsh);
+      loc = ONEDGE; // p is on edge [c,a].
+    } else {
+      loc = ONFACE; // p is on face [a,b,c].
+    }
+  } // if (rflag)
+
+  return loc;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// sscoutsegment()    Look for a segment in the surface triangulation.       //
+//                                                                           //
+// The segment is given by the origin of 'searchsh' and 'endpt'.             //
+//                                                                           //
+// If an edge in T is found matching this segment, the segment is "locked"   //
+// in T at the edge.  Otherwise, flip the first edge in T that the segment   //
+// crosses. Continue the search from the flipped face.                       //
+//                                                                           //
+// This routine uses 'orisent3d' to determine the search direction. It uses  //
+// 'dummypoint' as the 'lifted point' in 3d, and it assumes that it (dummy-  //
+// point) lies above the 'searchsh' (w.r.t the Right-hand rule).             //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+enum tetgenmesh::interresult tetgenmesh::sscoutsegment(face *searchsh, 
+  point endpt, int insertsegflag, int reporterrorflag, int chkencflag)
+{
+  face flipshs[2], neighsh;
+  point startpt, pa, pb, pc, pd;
+  enum interresult dir;
+  enum {MOVE_AB, MOVE_CA} nextmove;
+  REAL ori_ab, ori_ca, len;
+
+  // The origin of 'searchsh' is fixed.
+  startpt = sorg(*searchsh); 
+  nextmove = MOVE_AB; // Avoid compiler warning.
+
+  if (b->verbose > 2) {
+    printf("      Scout segment (%d, %d).\n", pointmark(startpt),
+           pointmark(endpt));
+  }
+  len = distance(startpt, endpt);
+
+  // Search an edge in 'searchsh' on the path of this segment.
+  while (1) {
+
+    pb = sdest(*searchsh);
+    if (pb == endpt) {
+      dir = SHAREEDGE; // Found!
+      break;
+    }
+
+    pc = sapex(*searchsh);
+    if (pc == endpt) {
+      senext2self(*searchsh);
+      sesymself(*searchsh);
+      dir = SHAREEDGE; // Found!
+      break;
+    }
+
+
+    // Round the results.
+    if ((sqrt(triarea(startpt, pb, endpt)) / len) < b->epsilon) {
+      ori_ab = 0.0;
+    } else {
+      ori_ab = orient3d(startpt, pb, dummypoint, endpt);
+    }
+    if ((sqrt(triarea(pc, startpt, endpt)) / len) < b->epsilon) {
+      ori_ca = 0.0;
+    } else {
+      ori_ca = orient3d(pc, startpt, dummypoint, endpt);
+    }
+
+    if (ori_ab < 0) {
+      if (ori_ca < 0) { // (--)
+        // Both sides are viable moves.
+        if (randomnation(2)) {
+          nextmove = MOVE_CA;
+        } else {
+          nextmove = MOVE_AB;
+        }
+      } else { // (-#)
+        nextmove = MOVE_AB;
+      }
+    } else {
+      if (ori_ca < 0) { // (#-)
+        nextmove = MOVE_CA;
+      } else {
+        if (ori_ab > 0) {
+          if (ori_ca > 0) { // (++)
+            // The segment intersects with edge [b, c].
+            dir = ACROSSEDGE;
+            break;
+          } else { // (+0)
+            // The segment collinear with edge [c, a].
+            senext2self(*searchsh);
+            sesymself(*searchsh); 
+            dir = ACROSSVERT;
+            break;
+          }
+        } else {
+          if (ori_ca > 0) { // (0+)
+            // The segment is collinear with edge [a, b].
+            dir = ACROSSVERT;
+            break;
+          } else { // (00)
+            // startpt == endpt. Not possible.
+            terminatetetgen(this, 2);
+          }
+        }
+      }
+    }
+
+    // Move 'searchsh' to the next face, keep the origin unchanged.
+    if (nextmove == MOVE_AB) {
+      if (chkencflag) {
+        // Do not cross boundary.
+        if (isshsubseg(*searchsh)) {
+          return ACROSSEDGE; // ACROSS_SEG
+        }
+      }
+      spivot(*searchsh, neighsh);
+      if (neighsh.sh != NULL) {
+        if (sorg(neighsh) != pb) sesymself(neighsh);
+        senext(neighsh, *searchsh);
+      } else {
+        // This side (startpt->pb) is outside. It is caused by rounding error.
+        // Try the next side, i.e., (pc->startpt).
+        senext2(*searchsh, neighsh);
+        if (chkencflag) {
+          // Do not cross boundary.
+          if (isshsubseg(neighsh)) {
+            *searchsh = neighsh;
+            return ACROSSEDGE; // ACROSS_SEG
+          }
+        }
+        spivotself(neighsh);
+        if (sdest(neighsh) != pc) sesymself(neighsh);
+        *searchsh = neighsh;
+      }
+    } else { // MOVE_CA
+      senext2(*searchsh, neighsh);
+      if (chkencflag) {
+        // Do not cross boundary.
+        if (isshsubseg(neighsh)) {
+          *searchsh = neighsh;
+          return ACROSSEDGE; // ACROSS_SEG
+        }
+      }
+      spivotself(neighsh);
+      if (neighsh.sh != NULL) {
+        if (sdest(neighsh) != pc) sesymself(neighsh);
+        *searchsh = neighsh;
+      } else {
+        // The same reason as above. 
+        // Try the next side, i.e., (startpt->pb).
+        if (chkencflag) {
+          // Do not cross boundary.
+          if (isshsubseg(*searchsh)) {
+            return ACROSSEDGE; // ACROSS_SEG
+          }
+        }
+        spivot(*searchsh, neighsh);
+        if (sorg(neighsh) != pb) sesymself(neighsh);
+        senext(neighsh, *searchsh);
+      }
+    }
+  } // while
+
+  if (dir == SHAREEDGE) {
+    if (insertsegflag) {
+      // Insert the segment into the triangulation.
+      face newseg;
+      makeshellface(subsegs, &newseg);
+      setshvertices(newseg, startpt, endpt, NULL);
+      // Set the default segment marker.
+      setshellmark(newseg, -1);
+      ssbond(*searchsh, newseg);
+      spivot(*searchsh, neighsh);
+      if (neighsh.sh != NULL) {
+        ssbond(neighsh, newseg);
+      }
+    }
+    return dir;
+  }
+
+  if (dir == ACROSSVERT) {
+    // A point is found collinear with this segment.
+    if (reporterrorflag) {
+      point pp = sdest(*searchsh);
+      printf("PLC Error:  A vertex lies in a segment in facet #%d.\n",
+             shellmark(*searchsh));
+      printf("  Vertex:  [%d] (%g,%g,%g).\n",pointmark(pp),pp[0],pp[1],pp[2]);
+      printf("  Segment: [%d, %d]\n", pointmark(startpt), pointmark(endpt));
+    }
+    return dir;
+  }
+
+  if (dir == ACROSSEDGE) {
+    // Edge [b, c] intersects with the segment.
+    senext(*searchsh, flipshs[0]);
+    if (isshsubseg(flipshs[0])) {
+      if (reporterrorflag) {
+        REAL P[3], Q[3], tp = 0, tq = 0;
+        linelineint(startpt, endpt, pb, pc, P, Q, &tp, &tq);
+        printf("PLC Error:  Two segments intersect at point (%g,%g,%g),", 
+               P[0], P[1], P[2]);
+        printf(" in facet #%d.\n", shellmark(*searchsh));
+        printf("  Segment 1: [%d, %d]\n", pointmark(pb), pointmark(pc));
+        printf("  Segment 2: [%d, %d]\n", pointmark(startpt),pointmark(endpt));
+      }
+      return dir; // ACROSS_SEG
+    }
+    // Flip edge [b, c], queue unflipped edges (for Delaunay checks).
+    spivot(flipshs[0], flipshs[1]);
+    if (sorg(flipshs[1]) != sdest(flipshs[0])) sesymself(flipshs[1]);
+    flip22(flipshs, 1, 0);
+    // The flip may create an inverted triangle, check it.
+    pa = sapex(flipshs[1]);
+    pb = sapex(flipshs[0]);
+    pc = sorg(flipshs[0]);
+    pd = sdest(flipshs[0]);
+    // Check if pa and pb are on the different sides of [pc, pd]. 
+    // Re-use ori_ab, ori_ca for the tests.
+    ori_ab = orient3d(pc, pd, dummypoint, pb);
+    ori_ca = orient3d(pd, pc, dummypoint, pa);
+    if (ori_ab <= 0) {
+      flipshpush(&(flipshs[0])); 
+    } else if (ori_ca <= 0) {
+      flipshpush(&(flipshs[1])); 
+    }
+    // Set 'searchsh' s.t. its origin is 'startpt'.
+    *searchsh = flipshs[0];
+  }
+
+  return sscoutsegment(searchsh, endpt, insertsegflag, reporterrorflag, 
+                       chkencflag);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// scarveholes()    Remove triangles not in the facet.                       //
+//                                                                           //
+// This routine re-uses the two global arrays: caveshlist and caveshbdlist.  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::scarveholes(int holes, REAL* holelist)
+{
+  face *parysh, searchsh, neighsh;
+  enum locateresult loc;
+  int i, j;
+
+  // Get all triangles. Infect unprotected convex hull triangles. 
+  smarktest(recentsh);
+  caveshlist->newindex((void **) &parysh);
+  *parysh = recentsh;
+  for (i = 0; i < caveshlist->objects; i++) {
+    parysh = (face *) fastlookup(caveshlist, i);
+    searchsh = *parysh;
+    searchsh.shver = 0;
+    for (j = 0; j < 3; j++) {
+      spivot(searchsh, neighsh);
+      // Is this side on the convex hull?
+      if (neighsh.sh != NULL) {
+        if (!smarktested(neighsh)) {
+          smarktest(neighsh);
+          caveshlist->newindex((void **) &parysh);
+          *parysh = neighsh;
+        }
+      } else {
+        // A hull side. Check if it is protected by a segment.
+        if (!isshsubseg(searchsh)) {
+          // Not protected. Save this face.
+          if (!sinfected(searchsh)) {
+            sinfect(searchsh);
+            caveshbdlist->newindex((void **) &parysh);
+            *parysh = searchsh;
+          }
+        }
+      }
+      senextself(searchsh);
+    }
+  }
+
+  // Infect the triangles in the holes.
+  for (i = 0; i < 3 * holes; i += 3) {
+    searchsh = recentsh;
+    loc = slocate(&(holelist[i]), &searchsh, 1, 1, 0);
+    if (loc != OUTSIDE) {
+      sinfect(searchsh);
+      caveshbdlist->newindex((void **) &parysh);
+      *parysh = searchsh;
+    }
+  }
+
+  // Find and infect all exterior triangles.
+  for (i = 0; i < caveshbdlist->objects; i++) {
+    parysh = (face *) fastlookup(caveshbdlist, i);
+    searchsh = *parysh;
+    searchsh.shver = 0;
+    for (j = 0; j < 3; j++) {
+      spivot(searchsh, neighsh);
+      if (neighsh.sh != NULL) {
+        if (!isshsubseg(searchsh)) {
+          if (!sinfected(neighsh)) {
+            sinfect(neighsh);
+            caveshbdlist->newindex((void **) &parysh);
+            *parysh = neighsh;
+          }
+        } else {
+          sdissolve(neighsh); // Disconnect a protected face.
+        }
+      }
+      senextself(searchsh);
+    }
+  }
+
+  // Delete exterior triangles, unmark interior triangles.
+  for (i = 0; i < caveshlist->objects; i++) {
+    parysh = (face *) fastlookup(caveshlist, i);
+    if (sinfected(*parysh)) {
+      shellfacedealloc(subfaces, parysh->sh);
+    } else {
+      sunmarktest(*parysh);
+    }
+  }
+
+  caveshlist->restart();
+  caveshbdlist->restart();
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// unifysegments()    Remove redundant segments and create face links.       //
+//                                                                           //
+// After this routine, although segments are unique, but some of them may be //
+// removed later by mergefacet().  All vertices still have type FACETVERTEX. //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::unifysegments()
+{
+  badface *facelink = NULL, *newlinkitem, *f1, *f2;
+  face *facperverlist, sface;
+  face subsegloop, testseg;
+  point torg, tdest;
+  REAL ori1, ori2, ori3;
+  REAL n1[3], n2[3];
+  REAL cosang, ang, ang_tol;
+  int *idx2faclist;
+  int idx, k, m;
+
+  if (b->verbose > 1) {
+    printf("  Unifying segments.\n");
+  }
+  // The limit dihedral angle that two facets are not overlapping.
+  ang_tol = b->facet_overlap_ang_tol / 180.0 * PI;
+  if (ang_tol < 0.0) ang_tol = 0.0;
+
+  // Create a mapping from vertices to subfaces.
+  makepoint2submap(subfaces, idx2faclist, facperverlist);
+
+
+  subsegloop.shver = 0;
+  subsegs->traversalinit();
+  subsegloop.sh = shellfacetraverse(subsegs);
+  while (subsegloop.sh != (shellface *) NULL) {
+    torg = sorg(subsegloop);
+    tdest = sdest(subsegloop);
+
+    idx = pointmark(torg) - in->firstnumber;
+    // Loop through the set of subfaces containing 'torg'.  Get all the
+    //   subfaces containing the edge (torg, tdest). Save and order them
+    //   in 'sfacelist', the ordering is defined by the right-hand rule
+    //   with thumb points from torg to tdest.
+    for (k = idx2faclist[idx]; k < idx2faclist[idx + 1]; k++) {
+      sface = facperverlist[k];
+      // The face may be deleted if it is a duplicated face.
+      if (sface.sh[3] == NULL) continue;
+      // Search the edge torg->tdest.
+      if (sdest(sface) != tdest) {
+        senext2self(sface);
+        sesymself(sface);
+      }
+      if (sdest(sface) != tdest) continue;
+
+      // Save the face f in facelink.
+      if (flippool->items >= 2) {
+        f1 = facelink;
+        for (m = 0; m < flippool->items - 1; m++) {
+          f2 = f1->nextitem;
+          ori1 = orient3d(torg, tdest, sapex(f1->ss), sapex(f2->ss));
+          ori2 = orient3d(torg, tdest, sapex(f1->ss), sapex(sface));
+          if (ori1 > 0) {
+            // apex(f2) is below f1.
+            if (ori2 > 0) {
+              // apex(f) is below f1 (see Fig.1). 
+              ori3 = orient3d(torg, tdest, sapex(f2->ss), sapex(sface));
+              if (ori3 > 0) {
+                // apex(f) is below f2, insert it.
+                break; 
+              } else if (ori3 < 0) {
+                // apex(f) is above f2, continue.
+              } else { // ori3 == 0; 
+                // f is coplanar and codirection with f2.
+                report_overlapping_facets(&(f2->ss), &sface);
+                break;
+              }
+            } else if (ori2 < 0) {
+              // apex(f) is above f1 below f2, inset it (see Fig. 2).
+              break;
+            } else { // ori2 == 0;
+              // apex(f) is coplanar with f1 (see Fig. 5).
+              ori3 = orient3d(torg, tdest, sapex(f2->ss), sapex(sface));
+              if (ori3 > 0) {
+                // apex(f) is below f2, insert it.
+                break; 
+              } else {
+                // f is coplanar and codirection with f1.
+                report_overlapping_facets(&(f1->ss), &sface);
+                break;
+              }
+            }
+          } else if (ori1 < 0) {
+            // apex(f2) is above f1.
+            if (ori2 > 0) {
+              // apex(f) is below f1, continue (see Fig. 3).
+            } else if (ori2 < 0) {
+              // apex(f) is above f1 (see Fig.4).
+              ori3 = orient3d(torg, tdest, sapex(f2->ss), sapex(sface));
+              if (ori3 > 0) {
+                // apex(f) is below f2, insert it.
+                break;
+              } else if (ori3 < 0) {
+                // apex(f) is above f2, continue.
+              } else { // ori3 == 0;
+                // f is coplanar and codirection with f2.
+                report_overlapping_facets(&(f2->ss), &sface);
+                break;
+              }
+            } else { // ori2 == 0;
+              // f is coplanar and with f1 (see Fig. 6).
+              ori3 = orient3d(torg, tdest, sapex(f2->ss), sapex(sface));
+              if (ori3 > 0) {
+                // f is also codirection with f1.
+                report_overlapping_facets(&(f1->ss), &sface);
+                break;
+              } else {
+                // f is above f2, continue.
+              }
+            }
+          } else { // ori1 == 0;
+            // apex(f2) is coplanar with f1. By assumption, f1 is not
+            //   coplanar and codirection with f2.
+            if (ori2 > 0) {
+              // apex(f) is below f1, continue (see Fig. 7).
+            } else if (ori2 < 0) {
+              // apex(f) is above f1, insert it (see Fig. 7).
+              break;
+            } else { // ori2 == 0.
+              // apex(f) is coplanar with f1 (see Fig. 8).
+              // f is either codirection with f1 or is codirection with f2. 
+              facenormal(torg, tdest, sapex(f1->ss), n1, 1, NULL);
+              facenormal(torg, tdest, sapex(sface), n2, 1, NULL);
+              if (dot(n1, n2) > 0) {
+                report_overlapping_facets(&(f1->ss), &sface);
+              } else {
+                report_overlapping_facets(&(f2->ss), &sface);
+              }
+              break;
+            }
+          }
+          // Go to the next item;
+          f1 = f2;
+        } // for (m = 0; ...)
+        if (sface.sh[3] != NULL) {
+          // Insert sface between f1 and f2.
+          newlinkitem = (badface *) flippool->alloc();
+          newlinkitem->ss = sface;
+          newlinkitem->nextitem = f1->nextitem;
+          f1->nextitem = newlinkitem;
+        }
+      } else if (flippool->items == 1) {
+        f1 = facelink;
+        // Make sure that f is not coplanar and codirection with f1.
+        ori1 = orient3d(torg, tdest, sapex(f1->ss), sapex(sface));
+        if (ori1 == 0) {
+          // f is coplanar with f1 (see Fig. 8).
+          facenormal(torg, tdest, sapex(f1->ss), n1, 1, NULL);
+          facenormal(torg, tdest, sapex(sface), n2, 1, NULL);
+          if (dot(n1, n2) > 0) {
+            // The two faces are codirectional as well.
+            report_overlapping_facets(&(f1->ss), &sface);
+          }
+        }
+        // Add this face to link if it is not deleted.
+        if (sface.sh[3] != NULL) {
+          // Add this face into link.
+          newlinkitem = (badface *) flippool->alloc();
+          newlinkitem->ss = sface;
+          newlinkitem->nextitem = NULL;
+          f1->nextitem = newlinkitem;
+        }
+      } else {
+        // The first face.
+        newlinkitem = (badface *) flippool->alloc();
+        newlinkitem->ss = sface;
+        newlinkitem->nextitem = NULL;
+        facelink = newlinkitem;
+      }
+    } // for (k = idx2faclist[idx]; ...)
+
+
+    // Set the connection between this segment and faces containing it,
+    //   at the same time, remove redundant segments.
+    f1 = facelink;
+    for (k = 0; k < flippool->items; k++) {
+      sspivot(f1->ss, testseg);
+      // If 'testseg' is not 'subsegloop' and is not dead, it is redundant.
+      if ((testseg.sh != subsegloop.sh) && (testseg.sh[3] != NULL)) {
+        shellfacedealloc(subsegs, testseg.sh);
+      }
+      // Bonds the subface and the segment together.
+      ssbond(f1->ss, subsegloop);
+      f1 = f1->nextitem;
+    }
+
+    // Create the face ring at the segment.
+    if (flippool->items > 1) {
+      f1 = facelink;
+      for (k = 1; k <= flippool->items; k++) {
+        k < flippool->items ? f2 = f1->nextitem : f2 = facelink;
+        // Calculate the dihedral angle between the two facet.
+        facenormal(torg, tdest, sapex(f1->ss), n1, 1, NULL);
+        facenormal(torg, tdest, sapex(f2->ss), n2, 1, NULL);
+        cosang = dot(n1, n2) / (sqrt(dot(n1, n1)) * sqrt(dot(n2, n2)));
+        // Rounding.
+        if (cosang > 1.0) cosang = 1.0;
+        else if (cosang < -1.0) cosang = -1.0;
+        ang = acos(cosang);
+        if (ang < ang_tol) {
+          // Two facets are treated as overlapping each other.
+          report_overlapping_facets(&(f1->ss), &(f2->ss), ang);
+        } else {
+          // Record the smallest input dihedral angle.
+          if (ang < minfacetdihed) {
+            minfacetdihed = ang;
+          }
+          sbond1(f1->ss, f2->ss);
+        }
+        f1 = f2;
+      }
+    }
+
+    flippool->restart();
+
+    // Are there length constraints?
+    if (b->quality && (in->segmentconstraintlist != (REAL *) NULL)) {
+      int e1, e2;
+      REAL len;
+      for (k = 0; k < in->numberofsegmentconstraints; k++) {
+        e1 = (int) in->segmentconstraintlist[k * 3];
+        e2 = (int) in->segmentconstraintlist[k * 3 + 1];
+        if (((pointmark(torg) == e1) && (pointmark(tdest) == e2)) ||
+            ((pointmark(torg) == e2) && (pointmark(tdest) == e1))) {
+          len = in->segmentconstraintlist[k * 3 + 2];
+          setareabound(subsegloop, len);
+          break;
+        }
+      }
+    }
+
+    subsegloop.sh = shellfacetraverse(subsegs);
+  }
+
+  delete [] idx2faclist;
+  delete [] facperverlist;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// identifyinputedges()    Identify input edges.                             //
+//                                                                           //
+// A set of input edges is provided in the 'in->edgelist'.  We find these    //
+// edges in the surface mesh and make them segments of the mesh.             //
+//                                                                           //
+// It is possible that an input edge is not in any facet, i.e.,it is a float-//
+// segment inside the volume.                                                //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::identifyinputedges(point *idx2verlist)
+{
+  face* shperverlist;
+  int* idx2shlist;
+  face searchsh, neighsh;
+  face segloop, checkseg, newseg;
+  point checkpt, pa = NULL, pb = NULL;
+  int *endpts;
+  int edgemarker;
+  int idx, i, j;
+
+  int e1, e2;
+  REAL len;
+
+  if (!b->quiet) {
+    printf("Inserting edges ...\n");
+  }
+
+  // Construct a map from points to subfaces.
+  makepoint2submap(subfaces, idx2shlist, shperverlist);
+
+  // Process the set of input edges.
+  for (i = 0; i < in->numberofedges; i++) {
+    endpts = &(in->edgelist[(i << 1)]);
+    if (endpts[0] == endpts[1]) {
+      if (!b->quiet) {
+        printf("Warning:  Edge #%d is degenerated. Skipped.\n", i);
+      }
+      continue; // Skip a degenerated edge.
+    }
+    // Recall that all existing segments have a default marker '-1'. 
+    // We assign all identified segments a default marker '-2'.
+    edgemarker = in->edgemarkerlist ? in->edgemarkerlist[i] : -2;
+
+    // Find a face contains the edge.
+    newseg.sh = NULL;
+    searchsh.sh = NULL;
+    idx = endpts[0] - in->firstnumber;
+    for (j = idx2shlist[idx]; j < idx2shlist[idx + 1]; j++) {
+      checkpt = sdest(shperverlist[j]);
+      if (pointmark(checkpt) == endpts[1]) {
+        searchsh = shperverlist[j];
+        break; // Found.
+      } else {
+        checkpt = sapex(shperverlist[j]);
+        if (pointmark(checkpt) == endpts[1]) {
+          senext2(shperverlist[j], searchsh);
+          sesymself(searchsh);
+          break;
+        }
+      }
+    } // j
+
+    if (searchsh.sh != NULL) {
+      // Check if this edge is already a segment of the mesh.
+      sspivot(searchsh, checkseg);
+      if (checkseg.sh != NULL) {
+        // This segment already exist.
+        newseg = checkseg;
+      } else {
+        // Create a new segment at this edge.
+        pa = sorg(searchsh);
+        pb = sdest(searchsh);
+        makeshellface(subsegs, &newseg);
+        setshvertices(newseg, pa, pb, NULL);
+        ssbond(searchsh, newseg);
+        spivot(searchsh, neighsh);
+        if (neighsh.sh != NULL) {
+          ssbond(neighsh, newseg);
+        }
+      }
+    } else {
+      // It is a dangling segment (not belong to any facets).
+      // Get the two endpoints of this segment.
+      pa = idx2verlist[endpts[0]];
+      pb = idx2verlist[endpts[1]];
+      if (pa == pb) {
+        if (!b->quiet) {
+          printf("Warning:  Edge #%d is degenerated. Skipped.\n", i);
+        }
+        continue;
+      }
+      // Check if segment [a,b] already exists.
+      // TODO: Change the brute-force search. Slow!
+      point *ppt;
+      subsegs->traversalinit();
+      segloop.sh = shellfacetraverse(subsegs);
+      while (segloop.sh != NULL) {
+        ppt = (point *) &(segloop.sh[3]);
+        if (((ppt[0] == pa) && (ppt[1] == pb)) ||
+            ((ppt[0] == pb) && (ppt[1] == pa))) {
+          // Found!
+          newseg = segloop; 
+          break;
+        }
+        segloop.sh = shellfacetraverse(subsegs);
+      }
+      if (newseg.sh == NULL) {
+        makeshellface(subsegs, &newseg);
+        setshvertices(newseg, pa, pb, NULL);
+      }
+    }
+
+    setshellmark(newseg, edgemarker);
+
+    if (b->quality && (in->segmentconstraintlist != (REAL *) NULL)) {
+      for (i = 0; i < in->numberofsegmentconstraints; i++) {
+        e1 = (int) in->segmentconstraintlist[i * 3];
+        e2 = (int) in->segmentconstraintlist[i * 3 + 1];
+        if (((pointmark(pa) == e1) && (pointmark(pb) == e2)) ||
+            ((pointmark(pa) == e2) && (pointmark(pb) == e1))) {
+          len = in->segmentconstraintlist[i * 3 + 2];
+          setareabound(newseg, len);
+          break;
+        }
+      }
+    }
+  } // i
+
+  delete [] shperverlist;
+  delete [] idx2shlist;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// mergefacets()    Merge adjacent facets.                                   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::mergefacets()
+{
+  face parentsh, neighsh, neineish;
+  face segloop;
+  point pa, pb, pc, pd;
+  REAL n1[3], n2[3];
+  REAL cosang, cosang_tol;
+
+
+  // Allocate an array to save calcaulated dihedral angles at segments.
+  arraypool *dihedangarray = new arraypool(sizeof(double), 10);
+  REAL *paryang = NULL;
+
+  // First, remove coplanar segments.
+  // The dihedral angle bound for two different facets.
+  cosang_tol = cos(b->facet_separate_ang_tol / 180.0 * PI);
+
+  subsegs->traversalinit();
+  segloop.sh = shellfacetraverse(subsegs);
+  while (segloop.sh != (shellface *) NULL) {
+    // Only remove a segment if it has a marker '-1'.
+    if (shellmark(segloop) != -1) {
+      segloop.sh = shellfacetraverse(subsegs);
+      continue;
+    }
+    spivot(segloop, parentsh);
+    if (parentsh.sh != NULL) {
+      spivot(parentsh, neighsh);
+      if (neighsh.sh != NULL) {
+        spivot(neighsh, neineish);
+        if (neineish.sh == parentsh.sh) {
+          // Exactly two subfaces at this segment.
+          // Only merge them if they have the same boundary marker.
+          if (shellmark(parentsh) == shellmark(neighsh)) {
+            pa = sorg(segloop);
+            pb = sdest(segloop);
+            pc = sapex(parentsh);
+            pd = sapex(neighsh);
+            // Calculate the dihedral angle at the segment [a,b].
+            facenormal(pa, pb, pc, n1, 1, NULL);
+            facenormal(pa, pb, pd, n2, 1, NULL);
+            cosang = dot(n1, n2) / (sqrt(dot(n1, n1)) * sqrt(dot(n2, n2)));
+            if (cosang < cosang_tol) {
+              ssdissolve(parentsh);
+              ssdissolve(neighsh);
+              shellfacedealloc(subsegs, segloop.sh);
+              // Add the edge to flip stack.
+              flipshpush(&parentsh);
+            } else {
+              // Save 'cosang' to avoid re-calculate it.
+              // Re-use the pointer at the first segment.
+              dihedangarray->newindex((void **) &paryang);
+              *paryang = cosang;
+              segloop.sh[6] = (shellface) paryang;
+            }
+          } 
+        } // if (neineish.sh == parentsh.sh)
+      }
+    }
+    segloop.sh = shellfacetraverse(subsegs);
+  }
+
+  // Second, remove ridge segments at small angles.
+  // The dihedral angle bound for two different facets.
+  cosang_tol = cos(b->facet_small_ang_tol / 180.0 * PI);
+  REAL cosang_sep_tol = cos((b->facet_separate_ang_tol - 5.0) / 180.0 * PI);
+  face shloop;
+  face seg1, seg2;
+  REAL cosang1, cosang2;
+  int i, j;
+
+  subfaces->traversalinit();
+  shloop.sh = shellfacetraverse(subfaces);
+  while (shloop.sh != (shellface *) NULL) {
+    for (i = 0; i < 3; i++) {
+      if (isshsubseg(shloop)) {
+        senext(shloop, neighsh);
+        if (isshsubseg(neighsh)) {
+          // Found two segments sharing at one vertex.
+          // Check if they form a small angle.
+          pa = sorg(shloop);
+          pb = sdest(shloop);
+          pc = sapex(shloop);
+          for (j = 0; j < 3; j++) n1[j] = pa[j] - pb[j];
+          for (j = 0; j < 3; j++) n2[j] = pc[j] - pb[j];
+          cosang = dot(n1, n2) / (sqrt(dot(n1, n1)) * sqrt(dot(n2, n2)));
+          if (cosang > cosang_tol) {
+            // Found a small angle.
+            segloop.sh = NULL;
+            sspivot(shloop, seg1);
+            sspivot(neighsh, seg2);
+            if (seg1.sh[6] != NULL) {
+              paryang = (REAL *) (seg1.sh[6]);
+              cosang1 = *paryang;
+            } else {
+              cosang1 = 1.0; // 0 degree;
+            }
+            if (seg2.sh[6] != NULL) {
+              paryang = (REAL *) (seg2.sh[6]);
+              cosang2 = *paryang;
+            } else {
+              cosang2 = 1.0; // 0 degree;
+            }
+            if (cosang1 < cosang_sep_tol) {
+              if (cosang2 < cosang_sep_tol) {
+                if (cosang1 < cosang2) {
+                  segloop = seg1;
+                } else {
+                  segloop = seg2;
+                }
+              } else {
+                segloop = seg1;
+              }
+            } else {
+              if (cosang2 < cosang_sep_tol) {
+                segloop = seg2;
+              }
+            }
+            if (segloop.sh != NULL) {
+              // Remove this segment.
+              segloop.shver = 0;
+              spivot(segloop, parentsh);
+              spivot(parentsh, neighsh);
+              ssdissolve(parentsh);
+              ssdissolve(neighsh);
+              shellfacedealloc(subsegs, segloop.sh);
+              // Add the edge to flip stack.
+              flipshpush(&parentsh);
+              break;
+            }
+          }
+        } // if (isshsubseg)
+      } // if (isshsubseg)
+      senextself(shloop);
+    }
+    shloop.sh = shellfacetraverse(subfaces);
+  }
+
+  delete dihedangarray;
+
+  if (flipstack != NULL) {
+    lawsonflip(); // Recover Delaunayness.
+  }
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// finddirection()    Find the tet on the path from one point to another.    //
+//                                                                           //
+// The path starts from 'searchtet''s origin and ends at 'endpt'. On finish, //
+// 'searchtet' contains a tet on the path, its origin does not change.       //
+//                                                                           //
+// The return value indicates one of the following cases (let 'searchtet' be //
+// abcd, a is the origin of the path):                                       //
+//   - ACROSSVERT, edge ab is collinear with the path;                       //
+//   - ACROSSEDGE, edge bc intersects with the path;                         //
+//   - ACROSSFACE, face bcd intersects with the path.                        //
+//                                                                           //
+// WARNING: This routine is designed for convex triangulations, and will not //
+// generally work after the holes and concavities have been carved.          //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+enum tetgenmesh::interresult 
+  tetgenmesh::finddirection(triface* searchtet, point endpt)
+{
+  triface neightet;
+  point pa, pb, pc, pd;
+  enum {HMOVE, RMOVE, LMOVE} nextmove;
+  REAL hori, rori, lori;
+  int t1ver;
+  int s;
+
+  // The origin is fixed.
+  pa = org(*searchtet);
+  if ((point) searchtet->tet[7] == dummypoint) {
+    // A hull tet. Choose the neighbor of its base face.
+    decode(searchtet->tet[3], *searchtet);
+    // Reset the origin to be pa.
+    if ((point) searchtet->tet[4] == pa) {
+      searchtet->ver = 11;
+    } else if ((point) searchtet->tet[5] == pa) {
+      searchtet->ver = 3;
+    } else if ((point) searchtet->tet[6] == pa) {
+      searchtet->ver = 7;
+    } else {
+      searchtet->ver = 0;
+    }
+  }
+
+  pb = dest(*searchtet);
+  // Check whether the destination or apex is 'endpt'.
+  if (pb == endpt) {
+    // pa->pb is the search edge.
+    return ACROSSVERT;
+  }
+
+  pc = apex(*searchtet);
+  if (pc == endpt) {
+    // pa->pc is the search edge.
+    eprevesymself(*searchtet);
+    return ACROSSVERT;
+  }
+
+  // Walk through tets around pa until the right one is found.
+  while (1) {
+
+    pd = oppo(*searchtet);
+    // Check whether the opposite vertex is 'endpt'.
+    if (pd == endpt) {
+      // pa->pd is the search edge.
+      esymself(*searchtet);
+      enextself(*searchtet);
+      return ACROSSVERT;
+    }
+    // Check if we have entered outside of the domain.
+    if (pd == dummypoint) {
+      // This is possible when the mesh is non-convex.
+      if (nonconvex) {
+        return ACROSSFACE; // return ACROSSSUB; // Hit a bounday.
+      } else {
+        terminatetetgen(this, 2);
+      }
+    }
+
+    // Now assume that the base face abc coincides with the horizon plane,
+    //   and d lies above the horizon.  The search point 'endpt' may lie
+    //   above or below the horizon.  We test the orientations of 'endpt'
+    //   with respect to three planes: abc (horizon), bad (right plane),
+    //   and acd (left plane). 
+    hori = orient3d(pa, pb, pc, endpt);
+    rori = orient3d(pb, pa, pd, endpt);
+    lori = orient3d(pa, pc, pd, endpt);
+
+    // Now decide the tet to move.  It is possible there are more than one
+    //   tets are viable moves. Is so, randomly choose one. 
+    if (hori > 0) {
+      if (rori > 0) {
+        if (lori > 0) {
+          // Any of the three neighbors is a viable move.
+          s = randomnation(3); 
+          if (s == 0) {
+            nextmove = HMOVE;
+          } else if (s == 1) {
+            nextmove = RMOVE;
+          } else {
+            nextmove = LMOVE;
+          }
+        } else {
+          // Two tets, below horizon and below right, are viable.
+          if (randomnation(2)) {
+            nextmove = HMOVE;
+          } else {
+            nextmove = RMOVE;
+          }
+        }
+      } else {
+        if (lori > 0) {
+          // Two tets, below horizon and below left, are viable.
+          if (randomnation(2)) {
+            nextmove = HMOVE;
+          } else {
+            nextmove = LMOVE;
+          }
+        } else {
+          // The tet below horizon is chosen.
+          nextmove = HMOVE;
+        }
+      }
+    } else {
+      if (rori > 0) {
+        if (lori > 0) {
+          // Two tets, below right and below left, are viable.
+          if (randomnation(2)) {
+            nextmove = RMOVE;
+          } else {
+            nextmove = LMOVE;
+          }
+        } else {
+          // The tet below right is chosen.
+          nextmove = RMOVE;
+        }
+      } else {
+        if (lori > 0) {
+          // The tet below left is chosen.
+          nextmove = LMOVE;
+        } else {
+          // 'endpt' lies either on the plane(s) or across face bcd.
+          if (hori == 0) {
+            if (rori == 0) {
+              // pa->'endpt' is COLLINEAR with pa->pb.
+              return ACROSSVERT;
+            }
+            if (lori == 0) {
+              // pa->'endpt' is COLLINEAR with pa->pc.
+              eprevesymself(*searchtet); // [a,c,d]
+              return ACROSSVERT;
+            }
+            // pa->'endpt' crosses the edge pb->pc.
+            return ACROSSEDGE;
+          }
+          if (rori == 0) {
+            if (lori == 0) {
+              // pa->'endpt' is COLLINEAR with pa->pd.
+              esymself(*searchtet); // face bad.
+              enextself(*searchtet); // face [a,d,b]
+              return ACROSSVERT;
+            }
+            // pa->'endpt' crosses the edge pb->pd.
+            esymself(*searchtet); // face bad.
+            enextself(*searchtet); // face adb
+            return ACROSSEDGE;
+          }
+          if (lori == 0) {
+            // pa->'endpt' crosses the edge pc->pd.
+            eprevesymself(*searchtet); // [a,c,d]
+            return ACROSSEDGE;
+          }
+          // pa->'endpt' crosses the face bcd.
+          return ACROSSFACE;
+        }
+      }
+    }
+
+    // Move to the next tet, fix pa as its origin.
+    if (nextmove == RMOVE) {
+      fnextself(*searchtet);
+    } else if (nextmove == LMOVE) {
+      eprevself(*searchtet);
+      fnextself(*searchtet);
+      enextself(*searchtet);
+    } else { // HMOVE
+      fsymself(*searchtet);
+      enextself(*searchtet);
+    }
+    pb = dest(*searchtet);
+    pc = apex(*searchtet);
+
+  } // while (1)
+
+}
+
+
+//// steiner_cxx //////////////////////////////////////////////////////////////
+////                                                                       ////
+////                                                                       ////
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// checkflipeligibility()    A call back function for boundary recovery.     //
+//                                                                           //
+// 'fliptype' indicates which elementary flip will be performed: 1 : 2-to-3, //
+// and 2 : 3-to-2, respectively.                                             //
+//                                                                           //
+// 'pa, ..., pe' are the vertices involved in this flip, where [a,b,c] is    //
+// the flip face, and [d,e] is the flip edge. NOTE: 'pc' may be 'dummypoint',//
+// other points must not be 'dummypoint'.                                    //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::checkflipeligibility(int fliptype, point pa, point pb, 
+                                     point pc, point pd, point pe,
+                                     int level, int edgepivot,
+                                     flipconstraints* fc)
+{
+  point tmppts[3];
+  enum interresult dir;
+  int types[2], poss[4];
+  int intflag;
+  int rejflag = 0;
+  int i;
+
+  if (fc->seg[0] != NULL) {
+    // A constraining edge is given (e.g., for edge recovery).
+    if (fliptype == 1) {
+      // A 2-to-3 flip: [a,b,c] => [e,d,a], [e,d,b], [e,d,c].
+      tmppts[0] = pa;
+      tmppts[1] = pb;
+      tmppts[2] = pc;
+      for (i = 0; i < 3 && !rejflag; i++) {
+        if (tmppts[i] != dummypoint) {
+          // Test if the face [e,d,#] intersects the edge.
+          intflag = tri_edge_test(pe, pd, tmppts[i], fc->seg[0], fc->seg[1], 
+                                  NULL, 1, types, poss);
+          if (intflag == 2) {
+            // They intersect at a single point.
+            dir = (enum interresult) types[0];
+            if (dir == ACROSSFACE) {
+              // The interior of [e,d,#] intersect the segment.
+              rejflag = 1;
+            } else if (dir == ACROSSEDGE) {
+              if (poss[0] == 0) {
+                // The interior of [e,d] intersect the segment.
+                // Since [e,d] is the newly created edge. Reject this flip.
+                rejflag = 1; 
+              }
+            }
+          } else if (intflag == 4) {
+            // They may intersect at either a point or a line segment.
+            dir = (enum interresult) types[0];
+            if (dir == ACROSSEDGE) {
+              if (poss[0] == 0) {
+                // The interior of [e,d] intersect the segment.
+                // Since [e,d] is the newly created edge. Reject this flip.
+                rejflag = 1;
+              }
+            }
+          }
+        } // if (tmppts[0] != dummypoint)
+      } // i
+    } else if (fliptype == 2) {
+      // A 3-to-2 flip: [e,d,a], [e,d,b], [e,d,c] => [a,b,c]
+      if (pc != dummypoint) {
+        // Check if the new face [a,b,c] intersect the edge in its interior.
+        intflag = tri_edge_test(pa, pb, pc, fc->seg[0], fc->seg[1], NULL, 
+                                1, types, poss);
+        if (intflag == 2) {
+          // They intersect at a single point.
+          dir = (enum interresult) types[0];
+          if (dir == ACROSSFACE) {
+            // The interior of [a,b,c] intersect the segment.
+            rejflag = 1; // Do not flip.
+          }
+        } else if (intflag == 4) {
+          // [a,b,c] is coplanar with the edge. 
+          dir = (enum interresult) types[0];
+          if (dir == ACROSSEDGE) {
+            // The boundary of [a,b,c] intersect the segment.            
+            rejflag = 1; // Do not flip.
+          }
+        }
+      } // if (pc != dummypoint)
+    }
+  } // if (fc->seg[0] != NULL)
+
+  if ((fc->fac[0] != NULL) && !rejflag) {
+    // A constraining face is given (e.g., for face recovery).
+    if (fliptype == 1) {
+      // A 2-to-3 flip.
+      // Test if the new edge [e,d] intersects the face.
+      intflag = tri_edge_test(fc->fac[0], fc->fac[1], fc->fac[2], pe, pd, 
+                              NULL, 1, types, poss);
+      if (intflag == 2) {
+        // They intersect at a single point.
+        dir = (enum interresult) types[0];
+        if (dir == ACROSSFACE) {
+          rejflag = 1;
+        } else if (dir == ACROSSEDGE) {
+          rejflag = 1;
+        } 
+      } else if (intflag == 4) {
+        // The edge [e,d] is coplanar with the face.
+        // There may be two intersections.
+        for (i = 0; i < 2 && !rejflag; i++) {
+          dir = (enum interresult) types[i];
+          if (dir == ACROSSFACE) {
+            rejflag = 1;
+          } else if (dir == ACROSSEDGE) {
+            rejflag = 1;
+          }
+        }
+      }
+    } // if (fliptype == 1)
+  } // if (fc->fac[0] != NULL)
+
+  if ((fc->remvert != NULL) && !rejflag) {
+    // The vertex is going to be removed. Do not create a new edge which
+    //   contains this vertex.
+    if (fliptype == 1) {
+      // A 2-to-3 flip.
+      if ((pd == fc->remvert) || (pe == fc->remvert)) {
+        rejflag = 1;
+      }
+    }
+  }
+
+  if (fc->remove_large_angle && !rejflag) {
+    // Remove a large dihedral angle. Do not create a new small angle.
+    REAL cosmaxd = 0, diff;
+    if (fliptype == 1) {
+      // We assume that neither 'a' nor 'b' is dummypoint.
+      // A 2-to-3 flip: [a,b,c] => [e,d,a], [e,d,b], [e,d,c].
+      // The new tet [e,d,a,b] will be flipped later. Only two new tets:
+      //   [e,d,b,c] and [e,d,c,a] need to be checked.
+      if ((pc != dummypoint) && (pe != dummypoint) && (pd != dummypoint)) {
+        // Get the largest dihedral angle of [e,d,b,c].
+        tetalldihedral(pe, pd, pb, pc, NULL, &cosmaxd, NULL);
+        diff = cosmaxd - fc->cosdihed_in;
+        if (fabs(diff/fc->cosdihed_in) < b->epsilon) diff = 0.0; // Rounding.
+        if (diff <= 0) { //if (cosmaxd <= fc->cosdihed_in) {
+          rejflag = 1;
+        } else {
+          // Record the largest new angle.
+          if (cosmaxd < fc->cosdihed_out) {
+            fc->cosdihed_out = cosmaxd; 
+          }
+          // Get the largest dihedral angle of [e,d,c,a].
+          tetalldihedral(pe, pd, pc, pa, NULL, &cosmaxd, NULL);
+          diff = cosmaxd - fc->cosdihed_in;
+          if (fabs(diff/fc->cosdihed_in) < b->epsilon) diff = 0.0; // Rounding.
+          if (diff <= 0) { //if (cosmaxd <= fc->cosdihed_in) {
+            rejflag = 1;
+          } else {
+            // Record the largest new angle.
+            if (cosmaxd < fc->cosdihed_out) {
+              fc->cosdihed_out = cosmaxd; 
+            }
+          }
+        }
+      } // if (pc != dummypoint && ...)
+    } else if (fliptype == 2) {
+      // A 3-to-2 flip: [e,d,a], [e,d,b], [e,d,c] => [a,b,c]
+      // We assume that neither 'e' nor 'd' is dummypoint.
+      if (level == 0) {
+        // Both new tets [a,b,c,d] and [b,a,c,e] are new tets.
+        if ((pa != dummypoint) && (pb != dummypoint) && (pc != dummypoint)) {
+          // Get the largest dihedral angle of [a,b,c,d].
+          tetalldihedral(pa, pb, pc, pd, NULL, &cosmaxd, NULL);
+          diff = cosmaxd - fc->cosdihed_in;
+          if (fabs(diff/fc->cosdihed_in) < b->epsilon) diff = 0.0; // Rounding
+          if (diff <= 0) { //if (cosmaxd <= fc->cosdihed_in) {
+            rejflag = 1;
+          } else {
+            // Record the largest new angle.
+            if (cosmaxd < fc->cosdihed_out) {
+              fc->cosdihed_out = cosmaxd; 
+            }
+            // Get the largest dihedral angle of [b,a,c,e].
+            tetalldihedral(pb, pa, pc, pe, NULL, &cosmaxd, NULL);
+            diff = cosmaxd - fc->cosdihed_in;
+            if (fabs(diff/fc->cosdihed_in) < b->epsilon) diff = 0.0;// Rounding
+            if (diff <= 0) { //if (cosmaxd <= fc->cosdihed_in) {
+              rejflag = 1;
+            } else {
+              // Record the largest new angle.
+              if (cosmaxd < fc->cosdihed_out) {
+                fc->cosdihed_out = cosmaxd; 
+              }
+            }
+          }
+        }
+      } else { // level > 0
+        if (edgepivot == 1) {
+          // The new tet [a,b,c,d] will be flipped. Only check [b,a,c,e].
+          if ((pa != dummypoint) && (pb != dummypoint) && (pc != dummypoint)) {
+            // Get the largest dihedral angle of [b,a,c,e].
+            tetalldihedral(pb, pa, pc, pe, NULL, &cosmaxd, NULL);
+            diff = cosmaxd - fc->cosdihed_in;
+            if (fabs(diff/fc->cosdihed_in) < b->epsilon) diff = 0.0;// Rounding
+            if (diff <= 0) { //if (cosmaxd <= fc->cosdihed_in) {
+              rejflag = 1;
+            } else {
+              // Record the largest new angle.
+              if (cosmaxd < fc->cosdihed_out) {
+                fc->cosdihed_out = cosmaxd; 
+              }
+            }
+          }
+        } else {
+          // The new tet [b,a,c,e] will be flipped. Only check [a,b,c,d].
+          if ((pa != dummypoint) && (pb != dummypoint) && (pc != dummypoint)) {
+            // Get the largest dihedral angle of [b,a,c,e].
+            tetalldihedral(pa, pb, pc, pd, NULL, &cosmaxd, NULL);
+            diff = cosmaxd - fc->cosdihed_in;
+            if (fabs(diff/fc->cosdihed_in) < b->epsilon) diff = 0.0;// Rounding
+            if (diff <= 0) { //if (cosmaxd <= fc->cosdihed_in) {
+              rejflag = 1;
+            } else {
+              // Record the largest new angle.
+              if (cosmaxd < fc->cosdihed_out) {
+                fc->cosdihed_out = cosmaxd; 
+              }
+            }
+          }
+        } // edgepivot
+      } // level
+    }
+  }
+
+  return rejflag;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// removeedgebyflips()    Attempt to remove an edge by flips.                //
+//                                                                           //
+// 'flipedge' is a non-convex or flat edge [a,b,#,#] to be removed.          //
+//                                                                           //
+// The return value is a positive integer, it indicates whether the edge is  //
+// removed or not.  A value "2" means the edge is removed, otherwise, the    //
+// edge is not removed and the value (must >= 3) is the current number of    //
+// tets in the edge star.                                                    //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::removeedgebyflips(triface *flipedge, flipconstraints* fc)
+{
+  triface *abtets, spintet;
+  int t1ver; 
+  int n, nn, i;
+
+
+  if (checksubsegflag) {
+    // Do not flip a segment.
+    if (issubseg(*flipedge)) {
+      if (fc->collectencsegflag) {
+        face checkseg, *paryseg;
+        tsspivot1(*flipedge, checkseg);
+        if (!sinfected(checkseg)) {
+          // Queue this segment in list.
+          sinfect(checkseg);                
+          caveencseglist->newindex((void **) &paryseg);
+          *paryseg = checkseg;
+        }
+      }
+      return 0;
+    }
+  }
+
+  // Count the number of tets at edge [a,b].
+  n = 0;
+  spintet = *flipedge;
+  while (1) {
+    n++;
+    fnextself(spintet);
+    if (spintet.tet == flipedge->tet) break;
+  }
+  if (n < 3) {
+    // It is only possible when the mesh contains inverted tetrahedra.  
+    terminatetetgen(this, 2); // Report a bug
+  }
+
+  if ((b->flipstarsize > 0) && (n > b->flipstarsize)) {
+    // The star size exceeds the limit.
+    return 0; // Do not flip it.
+  }
+
+  // Allocate spaces.
+  abtets = new triface[n];
+  // Collect the tets at edge [a,b].
+  spintet = *flipedge;
+  i = 0;
+  while (1) {
+    abtets[i] = spintet;
+    setelemcounter(abtets[i], 1); 
+    i++;
+    fnextself(spintet);
+    if (spintet.tet == flipedge->tet) break;
+  }
+
+
+  // Try to flip the edge (level = 0, edgepivot = 0).
+  nn = flipnm(abtets, n, 0, 0, fc);
+
+
+  if (nn > 2) {
+    // Edge is not flipped. Unmarktest the remaining tets in Star(ab).
+    for (i = 0; i < nn; i++) {
+      setelemcounter(abtets[i], 0);
+    }
+    // Restore the input edge (needed by Lawson's flip).
+    *flipedge = abtets[0];
+  }
+
+  // Release the temporary allocated spaces.
+  // NOTE: fc->unflip must be 0.
+  int bakunflip = fc->unflip;
+  fc->unflip = 0;
+  flipnm_post(abtets, n, nn, 0, fc);
+  fc->unflip = bakunflip;
+
+  delete [] abtets;
+
+  return nn; 
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// removefacebyflips()    Remove a face by flips.                            //
+//                                                                           //
+// Return 1 if the face is removed. Otherwise, return 0.                     //
+//                                                                           //
+// ASSUMPTIONS:                                                              //
+//   - 'flipface' must not be a subface.                                     //
+//   - 'flipface' must not be a hull face.                                   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::removefacebyflips(triface *flipface, flipconstraints* fc)
+{
+  triface fliptets[3], flipedge;
+  point pa, pb, pc, pd, pe;
+  REAL ori;
+  int reducflag = 0;
+
+  fliptets[0] = *flipface;
+  fsym(*flipface, fliptets[1]);
+  pa = org(fliptets[0]);
+  pb = dest(fliptets[0]);
+  pc = apex(fliptets[0]);
+  pd = oppo(fliptets[0]);
+  pe = oppo(fliptets[1]);
+
+  ori = orient3d(pa, pb, pd, pe);
+  if (ori > 0) {
+    ori = orient3d(pb, pc, pd, pe);
+    if (ori > 0) {
+      ori = orient3d(pc, pa, pd, pe);
+      if (ori > 0) {
+        // Found a 2-to-3 flip.
+        reducflag = 1;
+      } else {
+        eprev(*flipface, flipedge); // [c,a]
+      }
+    } else {
+      enext(*flipface, flipedge); // [b,c]
+    }
+  } else {
+    flipedge = *flipface; // [a,b]
+  }
+
+  if (reducflag) {
+    // A 2-to-3 flip is found.
+    flip23(fliptets, 0, fc);
+    return 1;
+  } else {
+    // Try to flip the selected edge of this face.
+    if (removeedgebyflips(&flipedge, fc) == 2) {
+      return 1;
+    }
+  }
+
+  // Face is not removed.
+  return 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// recoveredge()    Recover an edge in current tetrahedralization.           //
+//                                                                           //
+// If the edge is recovered, 'searchtet' returns a tet containing the edge.  //
+//                                                                           //
+// This edge may intersect a set of faces and edges in the mesh.  All these  //
+// faces or edges are needed to be removed.                                  //
+//                                                                           //
+// If the parameter 'fullsearch' is set, it tries to flip any face or edge   //
+// that intersects the recovering edge.  Otherwise, only the face or edge    //
+// which is visible by 'startpt' is tried.                                   //
+//                                                                           //
+// The parameter 'sedge' is used to report self-intersection. If it is not   //
+// a NULL, it is EITHER a segment OR a subface that contains this edge.      //
+//                                                                           //
+// Note that this routine assumes that the tetrahedralization is convex.     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::recoveredgebyflips(point startpt, point endpt, face *sedge,
+                                   triface* searchtet, int fullsearch)
+{
+  flipconstraints fc;
+  enum interresult dir;
+
+  fc.seg[0] = startpt;
+  fc.seg[1] = endpt;
+  fc.checkflipeligibility = 1;
+
+  // The mainloop of the edge reocvery.
+  while (1) { // Loop I
+
+    // Search the edge from 'startpt'.
+    point2tetorg(startpt, *searchtet);
+    dir = finddirection(searchtet, endpt);
+    if (dir == ACROSSVERT) {
+      if (dest(*searchtet) == endpt) {
+        return 1; // Edge is recovered.
+      } else {
+        if (sedge) {
+          return report_selfint_edge(startpt, endpt, sedge, searchtet, dir);
+        } else {
+          return 0;
+        }
+      }
+    }
+
+    // The edge is missing. 
+
+    // Try to remove the first intersecting face/edge.
+    enextesymself(*searchtet); // Go to the opposite face.
+    if (dir == ACROSSFACE) {
+      if (checksubfaceflag) {
+        if (issubface(*searchtet)) {
+          if (sedge) {
+            return report_selfint_edge(startpt, endpt, sedge, searchtet, dir);
+          } else {
+            return 0; // Cannot flip a subface.
+          }
+        }
+      }
+      // Try to flip a crossing face.
+      if (removefacebyflips(searchtet, &fc)) {
+        continue;
+      }
+    } else if (dir == ACROSSEDGE) {
+      if (checksubsegflag) {
+        if (issubseg(*searchtet)) {
+          if (sedge) {
+            return report_selfint_edge(startpt, endpt, sedge, searchtet, dir);
+          } else {
+            return 0; // Cannot flip a segment.
+          }
+        }
+      }
+      // Try to flip an intersecting edge.
+      if (removeedgebyflips(searchtet, &fc) == 2) {
+        continue;
+      }
+    }
+
+    // The edge is missing.
+
+    if (fullsearch) {
+      // Try to flip one of the faces/edges which intersects the edge.
+      triface neightet, spintet;
+      point pa, pb, pc, pd;
+      badface bakface;
+      enum interresult dir1;
+      int types[2], poss[4], pos = 0;
+      int success = 0;
+      int t1ver; 
+      int i, j;
+
+      // Loop through the sequence of intersecting faces/edges from
+      //   'startpt' to 'endpt'.
+      point2tetorg(startpt, *searchtet);
+      dir = finddirection(searchtet, endpt);
+
+      // Go to the face/edge intersecting the searching edge.
+      enextesymself(*searchtet); // Go to the opposite face.
+      // This face/edge has been tried in previous step.
+
+      while (1) { // Loop I-I
+
+        // Find the next intersecting face/edge.
+        fsymself(*searchtet);
+        if (dir == ACROSSFACE) {
+          neightet = *searchtet;
+          j = (neightet.ver & 3); // j is the current face number.
+          for (i = j + 1; i < j + 4; i++) {
+            neightet.ver = (i % 4);
+            pa = org(neightet);
+            pb = dest(neightet);
+            pc = apex(neightet);
+            pd = oppo(neightet); // The above point.
+            if (tri_edge_test(pa,pb,pc,startpt,endpt, pd, 1, types, poss)) {
+              dir = (enum interresult) types[0];
+              pos = poss[0];
+              break;
+            } else {
+              dir = DISJOINT;
+              pos = 0;
+            }
+          } // i
+          // There must be an intersection face/edge.
+          if (dir == DISJOINT) {
+            terminatetetgen(this, 2);
+          }
+        } else if (dir == ACROSSEDGE) {
+          while (1) { // Loop I-I-I
+            // Check the two opposite faces (of the edge) in 'searchtet'.  
+            for (i = 0; i < 2; i++) {
+              if (i == 0) {
+                enextesym(*searchtet, neightet);
+              } else {
+                eprevesym(*searchtet, neightet);
+              }
+              pa = org(neightet);
+              pb = dest(neightet);
+              pc = apex(neightet);
+              pd = oppo(neightet); // The above point.
+              if (tri_edge_test(pa,pb,pc,startpt,endpt,pd,1, types, poss)) {
+                dir = (enum interresult) types[0];
+                pos = poss[0];
+                break; // for loop
+              } else {
+                dir = DISJOINT;
+                pos = 0;
+              }
+            } // i
+            if (dir != DISJOINT) {
+              // Find an intersection face/edge.
+              break;  // Loop I-I-I
+            }
+            // No intersection. Rotate to the next tet at the edge.
+            fnextself(*searchtet);
+          } // while (1) // Loop I-I-I
+        } else {
+          terminatetetgen(this, 2); // Report a bug
+        }
+
+        // Adjust to the intersecting edge/vertex.
+        for (i = 0; i < pos; i++) {
+          enextself(neightet);
+        }
+
+        if (dir == SHAREVERT) {
+          // Check if we have reached the 'endpt'.
+          pd = org(neightet);
+          if (pd == endpt) {
+            // Failed to recover the edge.
+            break; // Loop I-I
+          } else {
+            terminatetetgen(this, 2); // Report a bug
+          }
+        }
+
+        // The next to be flipped face/edge.
+        *searchtet = neightet;
+
+        // Bakup this face (tetrahedron).
+        bakface.forg = org(*searchtet);
+        bakface.fdest = dest(*searchtet);
+        bakface.fapex = apex(*searchtet);
+        bakface.foppo = oppo(*searchtet);
+
+        // Try to flip this intersecting face/edge.
+        if (dir == ACROSSFACE) {
+          if (checksubfaceflag) {
+            if (issubface(*searchtet)) {
+              if (sedge) {
+                return report_selfint_edge(startpt,endpt,sedge,searchtet,dir);
+              } else {
+                return 0; // Cannot flip a subface.
+              }
+            }
+          }
+          if (removefacebyflips(searchtet, &fc)) {
+            success = 1;
+            break; // Loop I-I 
+          }
+        } else if (dir == ACROSSEDGE) {
+          if (checksubsegflag) {
+            if (issubseg(*searchtet)) {
+              if (sedge) {
+                return report_selfint_edge(startpt,endpt,sedge,searchtet,dir);
+              } else {
+                return 0; // Cannot flip a segment.
+              }
+            }
+          }
+          if (removeedgebyflips(searchtet, &fc) == 2) {
+            success = 1;
+            break; // Loop I-I
+          }
+        } else if (dir == ACROSSVERT) {
+          if (sedge) {
+            //return report_selfint_edge(startpt, endpt, sedge, searchtet, dir);
+            terminatetetgen(this, 2);
+          } else {
+            return 0;
+          }
+        } else {
+          terminatetetgen(this, 2); 
+        }
+
+        // The face/edge is not flipped.
+        if ((searchtet->tet == NULL) ||
+            (org(*searchtet) != bakface.forg) ||
+            (dest(*searchtet) != bakface.fdest) ||
+            (apex(*searchtet) != bakface.fapex) ||
+            (oppo(*searchtet) != bakface.foppo)) {
+          // 'searchtet' was flipped. We must restore it.
+          point2tetorg(bakface.forg, *searchtet);
+          dir1 = finddirection(searchtet, bakface.fdest);
+          if (dir1 == ACROSSVERT) {
+            if (dest(*searchtet) == bakface.fdest) {
+              spintet = *searchtet;
+              while (1) {
+                if (apex(spintet) == bakface.fapex) {
+                  // Found the face.
+                  *searchtet = spintet;
+                  break;
+                }
+                fnextself(spintet);
+                if (spintet.tet == searchtet->tet) {
+                  searchtet->tet = NULL;
+                  break; // Not find.
+                }
+	          } // while (1)
+              if (searchtet->tet != NULL) {
+                if (oppo(*searchtet) != bakface.foppo) {
+                  fsymself(*searchtet);
+                  if (oppo(*searchtet) != bakface.foppo) {
+                    // The original (intersecting) tet has been flipped.
+                    searchtet->tet = NULL;
+                    break; // Not find.
+                  }
+                }
+              }
+            } else {
+              searchtet->tet = NULL; // Not find.
+            }
+          } else {
+            searchtet->tet = NULL; // Not find.
+          }
+          if (searchtet->tet == NULL) {
+            success = 0; // This face/edge has been destroyed.
+            break; // Loop I-I 
+          }
+        }
+      } // while (1) // Loop I-I
+
+      if (success) {
+        // One of intersecting faces/edges is flipped.
+        continue;
+      }
+
+    } // if (fullsearch)
+
+    // The edge is missing.
+    break; // Loop I
+
+  } // while (1) // Loop I
+
+  return 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// add_steinerpt_in_schoenhardtpoly()    Insert a Steiner point in a Schoen- //
+//                                       hardt polyhedron.                   //
+//                                                                           //
+// 'abtets' is an array of n tets which all share at the edge [a,b]. Let the //
+// tets are [a,b,p0,p1], [a,b,p1,p2], ..., [a,b,p_(n-2),p_(n-1)].  Moreover, //
+// the edge [p0,p_(n-1)] intersects all of the tets in 'abtets'.  A special  //
+// case is that the edge [p0,p_(n-1)] is coplanar with the edge [a,b].       //
+// Such set of tets arises when we want to recover an edge from 'p0' to 'p_  //
+// (n-1)', and the number of tets at [a,b] can not be reduced by any flip.   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::add_steinerpt_in_schoenhardtpoly(triface *abtets, int n,
+                                                 int chkencflag)
+{
+  triface worktet, *parytet;
+  triface faketet1, faketet2;
+  point pc, pd, steinerpt;
+  insertvertexflags ivf;
+  optparameters opm;
+  REAL vcd[3], sampt[3], smtpt[3];
+  REAL maxminvol = 0.0, minvol = 0.0, ori;
+  int success, maxidx = 0;
+  int it, i;
+
+
+  pc = apex(abtets[0]);   // pc = p0
+  pd = oppo(abtets[n-1]); // pd = p_(n-1)
+
+
+  // Find an optimial point in edge [c,d]. It is visible by all outer faces
+  //   of 'abtets', and it maxmizes the min volume.
+
+  // initialize the list of 2n boundary faces.
+  for (i = 0; i < n; i++) {    
+    edestoppo(abtets[i], worktet); // [p_i,p_i+1,a]
+    cavetetlist->newindex((void **) &parytet);
+    *parytet = worktet;
+    eorgoppo(abtets[i], worktet);  // [p_i+1,p_i,b]
+    cavetetlist->newindex((void **) &parytet);
+    *parytet = worktet;
+  }
+
+  int N = 100;
+  REAL stepi = 0.01;
+
+  // Search the point along the edge [c,d].
+  for (i = 0; i < 3; i++) vcd[i] = pd[i] - pc[i];
+
+  // Sample N points in edge [c,d].
+  for (it = 1; it < N; it++) {
+    for (i = 0; i < 3; i++) {
+      sampt[i] = pc[i] + (stepi * (double) it) * vcd[i];
+    }
+    for (i = 0; i < cavetetlist->objects; i++) {
+      parytet = (triface *) fastlookup(cavetetlist, i);
+      ori = orient3d(dest(*parytet), org(*parytet), apex(*parytet), sampt);
+      if (i == 0) {
+        minvol = ori;
+      } else {
+        if (minvol > ori) minvol = ori;
+      }
+    } // i
+    if (it == 1) {
+      maxminvol = minvol;
+      maxidx = it;
+    } else {
+      if (maxminvol < minvol) {
+        maxminvol = minvol;
+        maxidx = it;
+      } 
+    }
+  } // it
+
+  if (maxminvol <= 0) {
+    cavetetlist->restart();
+    return 0;
+  }
+
+  for (i = 0; i < 3; i++) {
+    smtpt[i] = pc[i] + (stepi * (double) maxidx) * vcd[i];
+  }
+
+  // Create two faked tets to hold the two non-existing boundary faces:
+  //   [d,c,a] and [c,d,b].
+  maketetrahedron(&faketet1);
+  setvertices(faketet1, pd, pc, org(abtets[0]), dummypoint);
+  cavetetlist->newindex((void **) &parytet);
+  *parytet = faketet1;
+  maketetrahedron(&faketet2);
+  setvertices(faketet2, pc, pd, dest(abtets[0]), dummypoint);
+  cavetetlist->newindex((void **) &parytet);
+  *parytet = faketet2;
+
+  // Point smooth options.
+  opm.max_min_volume = 1;
+  opm.numofsearchdirs = 20;
+  opm.searchstep = 0.001;  
+  opm.maxiter = 100; // Limit the maximum iterations.
+  opm.initval = 0.0; // Initial volume is zero.
+
+  // Try to relocate the point into the inside of the polyhedron.
+  success = smoothpoint(smtpt, cavetetlist, 1, &opm);
+
+  if (success) {
+    while (opm.smthiter == 100) {
+      // It was relocated and the prescribed maximum iteration reached. 
+      // Try to increase the search stepsize.
+      opm.searchstep *= 10.0;
+      //opm.maxiter = 100; // Limit the maximum iterations.
+      opm.initval = opm.imprval;
+      opm.smthiter = 0; // Init.
+      smoothpoint(smtpt, cavetetlist, 1, &opm);  
+    }
+  } // if (success)
+
+  // Delete the two faked tets.
+  tetrahedrondealloc(faketet1.tet);
+  tetrahedrondealloc(faketet2.tet);
+
+  cavetetlist->restart();
+
+  if (!success) {
+    return 0;
+  }
+
+
+  // Insert the Steiner point.
+  makepoint(&steinerpt, FREEVOLVERTEX);
+  for (i = 0; i < 3; i++) steinerpt[i] = smtpt[i];
+
+  // Insert the created Steiner point.
+  for (i = 0; i < n; i++) {
+    infect(abtets[i]);
+    caveoldtetlist->newindex((void **) &parytet);
+    *parytet = abtets[i];
+  }
+  worktet = abtets[0]; // No need point location.
+  ivf.iloc = (int) INSTAR;
+  ivf.chkencflag = chkencflag;
+  ivf.assignmeshsize = b->metric; 
+  if (ivf.assignmeshsize) {
+    // Search the tet containing 'steinerpt' for size interpolation.
+    locate(steinerpt, &(abtets[0]));
+    worktet = abtets[0];
+  }
+
+  // Insert the new point into the tetrahedralization T.
+  // Note that T is convex (nonconvex = 0).
+  if (insertpoint(steinerpt, &worktet, NULL, NULL, &ivf)) {
+    // The vertex has been inserted.
+    st_volref_count++; 
+    if (steinerleft > 0) steinerleft--;
+    return 1;
+  } else {
+    // Not inserted. 
+    pointdealloc(steinerpt);
+    return 0;
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// add_steinerpt_in_segment()    Add a Steiner point inside a segment.       //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::add_steinerpt_in_segment(face* misseg, int searchlevel)
+{
+  triface searchtet;
+  face *paryseg, candseg;
+  point startpt, endpt, pc, pd;
+  flipconstraints fc;
+  enum interresult dir;
+  REAL P[3], Q[3], tp, tq;
+  REAL len, smlen = 0, split = 0, split_q = 0;
+  int success;
+  int i;
+
+  startpt = sorg(*misseg);
+  endpt = sdest(*misseg);
+
+  fc.seg[0] = startpt;
+  fc.seg[1] = endpt;
+  fc.checkflipeligibility = 1;
+  fc.collectencsegflag = 1;
+
+  point2tetorg(startpt, searchtet);
+  dir = finddirection(&searchtet, endpt);
+  // Try to flip the first intersecting face/edge.
+  enextesymself(searchtet); // Go to the opposite face.
+
+  int bak_fliplinklevel = b->fliplinklevel;
+  b->fliplinklevel = searchlevel;
+
+  if (dir == ACROSSFACE) {
+    // A face is intersected with the segment. Try to flip it.
+    success = removefacebyflips(&searchtet, &fc);
+  } else if (dir == ACROSSEDGE) {
+    // An edge is intersected with the segment. Try to flip it.
+    success = removeedgebyflips(&searchtet, &fc);
+  }
+
+  split = 0;
+  for (i = 0; i < caveencseglist->objects; i++) {
+    paryseg = (face *) fastlookup(caveencseglist, i);
+    suninfect(*paryseg);
+    // Calculate the shortest edge between the two lines.
+    pc = sorg(*paryseg);
+    pd = sdest(*paryseg);
+    tp = tq = 0;
+    if (linelineint(startpt, endpt, pc, pd, P, Q, &tp, &tq)) {
+      // Does the shortest edge lie between the two segments? 
+      // Round tp and tq.
+      if ((tp > 0) && (tq < 1)) {
+        if (tp < 0.5) {
+          if (tp < (b->epsilon * 1e+3)) tp = 0.0;
+        } else {
+          if ((1.0 - tp) < (b->epsilon * 1e+3)) tp = 1.0;
+        }
+      }
+      if ((tp <= 0) || (tp >= 1)) continue; 
+      if ((tq > 0) && (tq < 1)) {
+        if (tq < 0.5) {
+          if (tq < (b->epsilon * 1e+3)) tq = 0.0;
+        } else {
+          if ((1.0 - tq) < (b->epsilon * 1e+3)) tq = 1.0;
+        }
+      }
+      if ((tq <= 0) || (tq >= 1)) continue;
+      // It is a valid shortest edge. Calculate its length.
+      len = distance(P, Q);
+      if (split == 0) {
+        smlen = len;
+        split = tp;
+        split_q = tq;
+        candseg = *paryseg;
+      } else {
+        if (len < smlen) {
+          smlen = len;
+          split = tp;
+          split_q = tq;
+          candseg = *paryseg;
+        }
+      }
+    }
+  }
+
+  caveencseglist->restart();
+  b->fliplinklevel = bak_fliplinklevel;
+
+  if (split == 0) {
+    // Found no crossing segment. 
+    return 0;
+  }
+
+  face splitsh;
+  face splitseg;
+  point steinerpt, *parypt;
+  insertvertexflags ivf;
+
+  if (b->addsteiner_algo == 1) {
+    // Split the segment at the closest point to a near segment.
+    makepoint(&steinerpt, FREESEGVERTEX);
+    for (i = 0; i < 3; i++) {
+      steinerpt[i] = startpt[i] + split * (endpt[i] - startpt[i]);
+    }
+  } else { // b->addsteiner_algo == 2
+    for (i = 0; i < 3; i++) {
+      P[i] = startpt[i] + split * (endpt[i] - startpt[i]);
+    }
+    pc = sorg(candseg);
+    pd = sdest(candseg);
+    for (i = 0; i < 3; i++) {
+      Q[i] = pc[i] + split_q * (pd[i] - pc[i]);
+    }
+    makepoint(&steinerpt, FREEVOLVERTEX);
+    for (i = 0; i < 3; i++) {
+      steinerpt[i] = 0.5 * (P[i] + Q[i]);
+    }
+  }
+
+  // We need to locate the point. Start searching from 'searchtet'.
+  if (split < 0.5) {
+    point2tetorg(startpt, searchtet);
+  } else {
+    point2tetorg(endpt, searchtet);
+  }
+  if (b->addsteiner_algo == 1) {
+    splitseg = *misseg;
+    spivot(*misseg, splitsh);
+  } else {
+    splitsh.sh = NULL;
+    splitseg.sh = NULL;
+  }
+  ivf.iloc = (int) OUTSIDE;
+  ivf.bowywat = 1;
+  ivf.lawson = 0;
+  ivf.rejflag = 0;
+  ivf.chkencflag = 0;
+  ivf.sloc = (int) ONEDGE;
+  ivf.sbowywat = 1;
+  ivf.splitbdflag = 0;
+  ivf.validflag = 1;
+  ivf.respectbdflag = 1;
+  ivf.assignmeshsize = b->metric; 
+
+  if (!insertpoint(steinerpt, &searchtet, &splitsh, &splitseg, &ivf)) {
+    pointdealloc(steinerpt);
+    return 0;
+  }
+
+  if (b->addsteiner_algo == 1) {
+    // Save this Steiner point (for removal).
+    //   Re-use the array 'subvertstack'.
+    subvertstack->newindex((void **) &parypt);
+    *parypt = steinerpt;
+    st_segref_count++;
+  } else { // b->addsteiner_algo == 2
+    // Queue the segment for recovery.
+    subsegstack->newindex((void **) &paryseg);
+    *paryseg = *misseg; 
+    st_volref_count++;
+  }
+  if (steinerleft > 0) steinerleft--;
+
+  return 1;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// addsteiner4recoversegment()    Add a Steiner point for recovering a seg.  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::addsteiner4recoversegment(face* misseg, int splitsegflag)
+{
+  triface *abtets, searchtet, spintet;
+  face splitsh;
+  face *paryseg;
+  point startpt, endpt;
+  point pa, pb, pd, steinerpt, *parypt;
+  enum interresult dir;
+  insertvertexflags ivf;
+  int types[2], poss[4];
+  int n, endi, success;
+  int t1ver;
+  int i;
+
+  startpt = sorg(*misseg);
+  if (pointtype(startpt) == FREESEGVERTEX) {
+    sesymself(*misseg);
+    startpt = sorg(*misseg);
+  }
+  endpt = sdest(*misseg);
+
+  // Try to recover the edge by adding Steiner points.
+  point2tetorg(startpt, searchtet);
+  dir = finddirection(&searchtet, endpt);
+  enextself(searchtet); 
+
+  if (dir == ACROSSFACE) {
+    // The segment is crossing at least 3 faces. Find the common edge of 
+    //   the first 3 crossing faces.
+    esymself(searchtet);
+    fsym(searchtet, spintet);
+    pd = oppo(spintet);
+    for (i = 0; i < 3; i++) {
+      pa = org(spintet);
+      pb = dest(spintet);
+      if (tri_edge_test(pa, pb, pd, startpt, endpt, NULL, 1, types, poss)) {
+        break; // Found the edge.
+      }
+      enextself(spintet);
+      eprevself(searchtet);
+    }
+    esymself(searchtet);        
+  } 
+
+  spintet = searchtet;
+  n = 0; endi = -1;
+  while (1) {
+    // Check if the endpt appears in the star.
+    if (apex(spintet) == endpt) {
+      endi = n; // Remember the position of endpt.
+    }
+    n++; // Count a tet in the star.
+    fnextself(spintet);
+    if (spintet.tet == searchtet.tet) break;
+  }
+
+  if (endi > 0) {
+    // endpt is also in the edge star
+    // Get all tets in the edge star.
+    abtets = new triface[n];
+    spintet = searchtet;
+    for (i = 0; i < n; i++) {
+      abtets[i] = spintet;
+      fnextself(spintet);
+    }
+
+    success = 0;
+
+    if (dir == ACROSSFACE) {
+      // Find a Steiner points inside the polyhedron.
+      if (add_steinerpt_in_schoenhardtpoly(abtets, endi, 0)) {
+        success = 1;
+      }
+    } else if (dir == ACROSSEDGE) {
+      // PLC check.
+      if (issubseg(searchtet)) {
+        terminatetetgen(this, 2);
+      }
+      if (n > 4) {
+        // In this case, 'abtets' is separated by the plane (containing the
+        //   two intersecting edges) into two parts, P1 and P2, where P1
+        //   consists of 'endi' tets: abtets[0], abtets[1], ..., 
+        //   abtets[endi-1], and P2 consists of 'n - endi' tets: 
+        //   abtets[endi], abtets[endi+1], abtets[n-1].
+        if (endi > 2) { // P1
+          // There are at least 3 tets in the first part.
+          if (add_steinerpt_in_schoenhardtpoly(abtets, endi, 0)) {
+            success++;
+          }
+        }
+        if ((n - endi) > 2) { // P2
+          // There are at least 3 tets in the first part.
+          if (add_steinerpt_in_schoenhardtpoly(&(abtets[endi]), n - endi, 0)) {
+            success++;
+          }
+        }
+      } else {
+        // In this case, a 4-to-4 flip should be re-cover the edge [c,d].
+        //   However, there will be invalid tets (either zero or negtive 
+        //   volume). Otherwise, [c,d] should already be recovered by the 
+        //   recoveredge() function.
+        terminatetetgen(this, 2);
+      }
+    } else {
+      terminatetetgen(this, 2);
+    }
+
+    delete [] abtets;
+
+    if (success) {
+      // Add the missing segment back to the recovering list.
+      subsegstack->newindex((void **) &paryseg);
+      *paryseg = *misseg;
+      return 1;
+    }
+  } // if (endi > 0)
+
+  if (!splitsegflag) {
+    return 0;
+  }
+
+  if (b->verbose > 2) {
+    printf("      Splitting segment (%d, %d)\n", pointmark(startpt), 
+           pointmark(endpt));
+  }
+  steinerpt = NULL;
+
+  if (b->addsteiner_algo > 0) { // -Y/1 or -Y/2
+    if (add_steinerpt_in_segment(misseg, 3)) {
+      return 1;
+    }
+    sesymself(*misseg);
+    if (add_steinerpt_in_segment(misseg, 3)) {
+      return 1;
+    }
+    sesymself(*misseg);
+  }
+
+
+
+
+  if (steinerpt == NULL) {
+    // Split the segment at its midpoint.
+    makepoint(&steinerpt, FREESEGVERTEX);
+    for (i = 0; i < 3; i++) {
+      steinerpt[i] = 0.5 * (startpt[i] + endpt[i]);
+    }
+
+    // We need to locate the point.
+    spivot(*misseg, splitsh);
+    ivf.iloc = (int) OUTSIDE;
+    ivf.bowywat = 1;
+    ivf.lawson = 0;
+    ivf.rejflag = 0;
+    ivf.chkencflag = 0;
+    ivf.sloc = (int) ONEDGE;
+    ivf.sbowywat = 1;
+    ivf.splitbdflag = 0;
+    ivf.validflag = 1;
+    ivf.respectbdflag = 1;
+    ivf.assignmeshsize = b->metric; 
+    if (!insertpoint(steinerpt, &searchtet, &splitsh, misseg, &ivf)) {
+      terminatetetgen(this, 2);
+    }
+  } // if (endi > 0)
+
+  // Save this Steiner point (for removal).
+  //   Re-use the array 'subvertstack'.
+  subvertstack->newindex((void **) &parypt);
+  *parypt = steinerpt;
+
+  st_segref_count++;
+  if (steinerleft > 0) steinerleft--;
+
+  return 1;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// recoversegments()    Recover all segments.                                //
+//                                                                           //
+// All segments need to be recovered are in 'subsegstack'.                   //
+//                                                                           //
+// This routine first tries to recover each segment by only using flips. If  //
+// no flip is possible, and the flag 'steinerflag' is set, it then tries to  //
+// insert Steiner points near or in the segment.                             //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::recoversegments(arraypool *misseglist, int fullsearch,
+                                int steinerflag)
+{
+  triface searchtet, spintet;
+  face sseg, *paryseg;
+  point startpt, endpt;
+  int success;
+  int t1ver;
+
+  long bak_inpoly_count = st_volref_count; 
+  long bak_segref_count = st_segref_count;
+
+  if (b->verbose > 1) {
+    printf("    Recover segments [%s level = %2d] #:  %ld.\n",
+           (b->fliplinklevel > 0) ? "fixed" : "auto",
+           (b->fliplinklevel > 0) ? b->fliplinklevel : autofliplinklevel,
+           subsegstack->objects);
+  }
+
+  // Loop until 'subsegstack' is empty.
+  while (subsegstack->objects > 0l) {
+    // seglist is used as a stack.
+    subsegstack->objects--;
+    paryseg = (face *) fastlookup(subsegstack, subsegstack->objects);
+    sseg = *paryseg;
+
+    // Check if this segment has been recovered.
+    sstpivot1(sseg, searchtet);
+    if (searchtet.tet != NULL) {
+      continue; // Not a missing segment.
+    }
+
+    startpt = sorg(sseg);
+    endpt = sdest(sseg);
+
+    if (b->verbose > 2) {
+      printf("      Recover segment (%d, %d).\n", pointmark(startpt), 
+             pointmark(endpt));
+    }
+
+    success = 0;
+
+    if (recoveredgebyflips(startpt, endpt, &sseg, &searchtet, 0)) {
+      success = 1;
+    } else {
+      // Try to recover it from the other direction.
+      if (recoveredgebyflips(endpt, startpt, &sseg, &searchtet, 0)) {
+        success = 1;
+      }
+    }
+
+    if (!success && fullsearch) {
+      if (recoveredgebyflips(startpt, endpt, &sseg, &searchtet, fullsearch)) {
+        success = 1;
+      }
+    }
+
+    if (success) {
+      // Segment is recovered. Insert it.
+      // Let the segment remember an adjacent tet.
+      sstbond1(sseg, searchtet);
+      // Bond the segment to all tets containing it.
+      spintet = searchtet;
+      do {
+        tssbond1(spintet, sseg);
+        fnextself(spintet);
+      } while (spintet.tet != searchtet.tet);
+    } else {
+      if (steinerflag > 0) {
+        // Try to recover the segment but do not split it.
+        if (addsteiner4recoversegment(&sseg, 0)) {
+          success = 1;
+        }
+        if (!success && (steinerflag > 1)) {
+          // Split the segment.
+          addsteiner4recoversegment(&sseg, 1);
+          success = 1;
+        }
+      }
+      if (!success) {
+        if (misseglist != NULL) {
+          // Save this segment.
+          misseglist->newindex((void **) &paryseg);
+          *paryseg = sseg;
+        }
+      }
+    }
+
+  } // while (subsegstack->objects > 0l)
+
+  if (steinerflag) {
+    if (b->verbose > 1) {
+      // Report the number of added Steiner points.
+      if (st_volref_count > bak_inpoly_count) {
+        printf("    Add %ld Steiner points in volume.\n", 
+               st_volref_count - bak_inpoly_count);
+      }
+      if (st_segref_count > bak_segref_count) {
+        printf("    Add %ld Steiner points in segments.\n", 
+               st_segref_count - bak_segref_count);
+      }
+    }
+  }
+
+  return 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// recoverfacebyflips()    Recover a face by flips.                          //
+//                                                                           //
+// 'pa', 'pb', and 'pc' are the three vertices of this face.  This routine   //
+// tries to recover it in the tetrahedral mesh. It is assumed that the three //
+// edges, i.e., pa->pb, pb->pc, and pc->pa all exist.                        //
+//                                                                           //
+// If the face is recovered, it is returned by 'searchtet'.                  //
+//                                                                           //
+// If 'searchsh' is not NULL, it is a subface to be recovered.  Its vertices //
+// must be pa, pb, and pc.  It is mainly used to check self-intersections.   //
+// Another use of this subface is to split it when a Steiner point is found  //
+// inside this subface.                                                      //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::recoverfacebyflips(point pa, point pb, point pc, 
+                                   face *searchsh, triface* searchtet)
+{
+  triface spintet, flipedge;
+  point pd, pe;
+  flipconstraints fc;
+  int types[2], poss[4], intflag;
+  int success;
+  int t1ver; 
+  int i, j;
+
+
+  fc.fac[0] = pa;
+  fc.fac[1] = pb;
+  fc.fac[2] = pc;
+  fc.checkflipeligibility = 1;
+  success = 0;
+
+  for (i = 0; i < 3 && !success; i++) {
+    while (1) {
+      // Get a tet containing the edge [a,b].
+      point2tetorg(fc.fac[i], *searchtet);
+      finddirection(searchtet, fc.fac[(i+1)%3]);
+      // Search the face [a,b,c]
+      spintet = *searchtet;
+      while (1) {
+        if (apex(spintet) == fc.fac[(i+2)%3]) {
+          // Found the face.
+          *searchtet = spintet;
+          // Return the face [a,b,c].
+          for (j = i; j > 0; j--) {
+            eprevself(*searchtet);
+          }
+          success = 1;
+          break;
+        }
+        fnextself(spintet);
+        if (spintet.tet == searchtet->tet) break;
+      } // while (1)
+      if (success) break;
+      // The face is missing. Try to recover it.
+      flipedge.tet = NULL;
+      // Find a crossing edge of this face.
+      spintet = *searchtet;
+      while (1) {
+        pd = apex(spintet);
+        pe = oppo(spintet);
+        if ((pd != dummypoint) && (pe != dummypoint)) {
+          // Check if [d,e] intersects [a,b,c]
+          intflag = tri_edge_test(pa, pb, pc, pd, pe, NULL, 1, types, poss);
+          if (intflag > 0) {
+            // By the assumption that all edges of the face exist, they can
+            //   only intersect at a single point.
+            if (intflag == 2) {
+              // Go to the edge [d,e].
+              edestoppo(spintet, flipedge); // [d,e,a,b]
+              if (searchsh != NULL) {
+                // Check the intersection type.
+                if ((types[0] == (int) ACROSSFACE) || 
+                    (types[0] == (int) ACROSSEDGE)) {
+                  // Check if [e,d] is a segment.
+                  if (issubseg(flipedge)) {
+                    return report_selfint_face(pa, pb, pc, searchsh, &flipedge,
+                                               intflag, types, poss);
+		          } else {
+				    // Check if [e,d] is an edge of a subface.
+					triface chkface = flipedge;
+					while (1) {
+					  if (issubface(chkface)) break;
+					  fsymself(chkface);
+					  if (chkface.tet == flipedge.tet) break;
+					}
+					if (issubface(chkface)) {
+					  // Two subfaces are intersecting.
+					  return report_selfint_face(pa, pb, pc,searchsh,&chkface,
+                                                 intflag, types, poss);
+					}
+				  }
+				} else if (types[0] == TOUCHFACE) {
+                  // This is possible when a Steiner point was added on it.
+				  point touchpt, *parypt;
+                  if (poss[1] == 0) {
+                    touchpt = pd; // pd is a coplanar vertex.
+                  } else {
+                    touchpt = pe; // pe is a coplanar vertex.
+                  }
+				  if (pointtype(touchpt) == FREEVOLVERTEX) {
+                    // A volume Steiner point was added in this subface.
+                    // Split this subface by this point.
+                    face checksh, *parysh;
+                    int siloc = (int) ONFACE;
+                    int sbowat = 0; // Only split this subface. A 1-to-3 flip.
+                    setpointtype(touchpt, FREEFACETVERTEX);
+                    sinsertvertex(touchpt, searchsh, NULL, siloc, sbowat, 0);
+                    st_volref_count--;
+                    st_facref_count++;
+                    // Queue this vertex for removal.
+                    subvertstack->newindex((void **) &parypt);
+                    *parypt = touchpt;
+                    // Queue new subfaces for recovery.
+                    // Put all new subfaces into stack for recovery.
+                    for (i = 0; i < caveshbdlist->objects; i++) {
+                      // Get an old subface at edge [a, b].
+                      parysh = (face *) fastlookup(caveshbdlist, i);
+                      spivot(*parysh, checksh); // The new subface [a, b, p].
+                      // Do not recover a deleted new face (degenerated).
+                      if (checksh.sh[3] != NULL) {
+                        subfacstack->newindex((void **) &parysh);
+                        *parysh = checksh;
+                      }
+                    }
+                    // Delete the old subfaces in sC(p).
+                    for (i = 0; i < caveshlist->objects; i++) {
+                      parysh = (face *) fastlookup(caveshlist, i);
+                      shellfacedealloc(subfaces, parysh->sh);
+                    }
+                    // Clear working lists.
+                    caveshlist->restart();
+                    caveshbdlist->restart();
+                    cavesegshlist->restart();
+                    // We can return this function.
+                    searchsh->sh = NULL; // It has been split.
+					return 1;
+                  } else {
+				    // Other cases may be due to a bug or a PLC error.
+					return report_selfint_face(pa, pb, pc, searchsh, &flipedge,
+                                               intflag, types, poss);
+				  }
+                } else {
+                  // The other intersection types: ACROSSVERT, TOUCHEDGE, 
+                  // SHAREVERTEX should not be possible or due to a PLC error.
+                  return report_selfint_face(pa, pb, pc, searchsh, &flipedge,
+                                             intflag, types, poss);
+                }
+              } // if (searchsh != NULL)
+            } else { // intflag == 4. Coplanar case.
+              terminatetetgen(this, 2); 
+            }
+            break;
+          } // if (intflag > 0)
+        }
+        fnextself(spintet);
+        if (spintet.tet == searchtet->tet) {
+          terminatetetgen(this, 2);
+        }
+      } // while (1)
+      // Try to flip the edge [d,e].
+      if (removeedgebyflips(&flipedge, &fc) == 2) {
+        // A crossing edge is removed.
+        continue; 
+      }
+      break;
+    } // while (1)
+  } // i
+
+  return success;
+}
+                                   
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// recoversubfaces()    Recover all subfaces.                                //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::recoversubfaces(arraypool *misshlist, int steinerflag)
+{
+  triface searchtet, neightet, spintet;
+  face searchsh, neighsh, neineish, *parysh;
+  face bdsegs[3];
+  point startpt, endpt, apexpt, *parypt;
+  point steinerpt;
+  insertvertexflags ivf;
+  int success;
+  int t1ver;
+  int i, j;
+
+  if (b->verbose > 1) {
+    printf("    Recover subfaces [%s level = %2d] #:  %ld.\n",
+           (b->fliplinklevel > 0) ? "fixed" : "auto",
+           (b->fliplinklevel > 0) ? b->fliplinklevel : autofliplinklevel,
+           subfacstack->objects);
+  }
+
+  // Loop until 'subfacstack' is empty.
+  while (subfacstack->objects > 0l) {
+
+    subfacstack->objects--;
+    parysh = (face *) fastlookup(subfacstack, subfacstack->objects);
+    searchsh = *parysh;
+
+    if (searchsh.sh[3] == NULL) continue; // Skip a dead subface.
+
+    stpivot(searchsh, neightet);
+    if (neightet.tet != NULL) continue; // Skip a recovered subface.
+
+
+    if (b->verbose > 2) {
+      printf("      Recover subface (%d, %d, %d).\n",pointmark(sorg(searchsh)),
+             pointmark(sdest(searchsh)), pointmark(sapex(searchsh)));
+    }
+
+    // The three edges of the face need to be existed first.
+    for (i = 0; i < 3; i++) {
+      sspivot(searchsh, bdsegs[i]);   
+      if (bdsegs[i].sh != NULL) {
+        // The segment must exist.
+        sstpivot1(bdsegs[i], searchtet);
+        if (searchtet.tet == NULL) {
+          terminatetetgen(this, 2);
+        }
+      } else {
+        // This edge is not a segment (due to a Steiner point).
+        // Check whether it exists or not.
+        success = 0;
+        startpt = sorg(searchsh);
+        endpt = sdest(searchsh);
+        point2tetorg(startpt, searchtet);
+        finddirection(&searchtet, endpt);
+        if (dest(searchtet) == endpt) {
+          success = 1;
+        } else {
+          // The edge is missing. Try to recover it.
+          if (recoveredgebyflips(startpt, endpt, &searchsh, &searchtet, 0)) {
+            success = 1;
+          } else {
+            if (recoveredgebyflips(endpt, startpt, &searchsh, &searchtet, 0)) {
+              success = 1;
+            }
+          }
+        }
+        if (success) {
+          // Insert a temporary segment to protect this edge.
+          makeshellface(subsegs, &(bdsegs[i]));
+          setshvertices(bdsegs[i], startpt, endpt, NULL);
+          smarktest2(bdsegs[i]); // It's a temporary segment.
+          // Insert this segment into surface mesh.
+          ssbond(searchsh, bdsegs[i]);
+          spivot(searchsh, neighsh);
+          if (neighsh.sh != NULL) {
+            ssbond(neighsh, bdsegs[i]);
+          }
+          // Insert this segment into tetrahedralization.
+          sstbond1(bdsegs[i], searchtet);
+          // Bond the segment to all tets containing it.
+          spintet = searchtet;
+          do {
+            tssbond1(spintet, bdsegs[i]);
+            fnextself(spintet);
+          } while (spintet.tet != searchtet.tet);
+        } else {
+          // An edge of this subface is missing. Can't recover this subface.
+          // Delete any temporary segment that has been created.
+          for (j = (i - 1); j >= 0; j--) {
+            if (smarktest2ed(bdsegs[j])) { 
+              spivot(bdsegs[j], neineish);
+                ssdissolve(neineish);
+                spivot(neineish, neighsh);
+                if (neighsh.sh != NULL) {
+                  ssdissolve(neighsh);
+                }
+              sstpivot1(bdsegs[j], searchtet);
+                spintet = searchtet;
+                while (1) {
+                  tssdissolve1(spintet);
+                  fnextself(spintet);
+                  if (spintet.tet == searchtet.tet) break;
+                }
+              shellfacedealloc(subsegs, bdsegs[j].sh);
+            }
+          } // j
+          if (steinerflag) {
+            // Add a Steiner point at the midpoint of this edge.
+            if (b->verbose > 2) {
+              printf("      Add a Steiner point in subedge (%d, %d).\n",
+                     pointmark(startpt), pointmark(endpt));
+            }
+            makepoint(&steinerpt, FREEFACETVERTEX);
+            for (j = 0; j < 3; j++) {
+              steinerpt[j] = 0.5 * (startpt[j] + endpt[j]);
+            }
+
+            point2tetorg(startpt, searchtet); // Start from 'searchtet'.
+            ivf.iloc = (int) OUTSIDE; // Need point location.
+            ivf.bowywat = 1;
+            ivf.lawson = 0;
+            ivf.rejflag = 0;
+            ivf.chkencflag = 0;
+            ivf.sloc = (int) ONEDGE;            
+            ivf.sbowywat = 1; // Allow flips in facet.
+            ivf.splitbdflag = 0;
+            ivf.validflag = 1;
+            ivf.respectbdflag = 1;
+            ivf.assignmeshsize = b->metric;
+            if (!insertpoint(steinerpt, &searchtet, &searchsh, NULL, &ivf)) {
+              terminatetetgen(this, 2);
+            }
+            // Save this Steiner point (for removal).
+            //   Re-use the array 'subvertstack'.
+            subvertstack->newindex((void **) &parypt);
+            *parypt = steinerpt;
+
+            st_facref_count++;
+            if (steinerleft > 0) steinerleft--;
+          } // if (steinerflag)
+          break;
+        }
+      }
+      senextself(searchsh);
+    } // i
+
+    if (i == 3) {
+      // Recover the subface.
+      startpt = sorg(searchsh);
+      endpt   = sdest(searchsh);
+      apexpt  = sapex(searchsh);
+
+      success = recoverfacebyflips(startpt,endpt,apexpt,&searchsh,&searchtet);
+
+      // Delete any temporary segment that has been created.
+      for (j = 0; j < 3; j++) {
+        if (smarktest2ed(bdsegs[j])) { 
+          spivot(bdsegs[j], neineish);
+            ssdissolve(neineish);
+            spivot(neineish, neighsh);
+            if (neighsh.sh != NULL) {
+              ssdissolve(neighsh);
+            }
+          sstpivot1(bdsegs[j], neightet);
+            spintet = neightet;
+            while (1) {
+              tssdissolve1(spintet);
+              fnextself(spintet);
+              if (spintet.tet == neightet.tet) break;
+            }
+          shellfacedealloc(subsegs, bdsegs[j].sh);
+        }
+      } // j
+
+      if (success) {
+        if (searchsh.sh != NULL) {
+          // Face is recovered. Insert it.
+          tsbond(searchtet, searchsh);
+          fsymself(searchtet);
+          sesymself(searchsh);
+          tsbond(searchtet, searchsh);
+        }
+      } else {
+        if (steinerflag) {
+          // Add a Steiner point at the barycenter of this subface.
+          if (b->verbose > 2) {
+            printf("      Add a Steiner point in subface (%d, %d, %d).\n",
+                   pointmark(startpt), pointmark(endpt), pointmark(apexpt));
+          }
+          makepoint(&steinerpt, FREEFACETVERTEX);
+          for (j = 0; j < 3; j++) {
+            steinerpt[j] = (startpt[j] + endpt[j] + apexpt[j]) / 3.0;
+          }
+
+          point2tetorg(startpt, searchtet); // Start from 'searchtet'.
+          ivf.iloc = (int) OUTSIDE; // Need point location.
+          ivf.bowywat = 1;
+          ivf.lawson = 0;
+          ivf.rejflag = 0;
+          ivf.chkencflag = 0;
+          ivf.sloc = (int) ONFACE;          
+          ivf.sbowywat = 1; // Allow flips in facet.
+          ivf.splitbdflag = 0;
+          ivf.validflag = 1;
+          ivf.respectbdflag = 1;
+          ivf.assignmeshsize = b->metric; 
+          if (!insertpoint(steinerpt, &searchtet, &searchsh, NULL, &ivf)) {
+            terminatetetgen(this, 2);
+          }
+          // Save this Steiner point (for removal).
+          //   Re-use the array 'subvertstack'.
+          subvertstack->newindex((void **) &parypt);
+          *parypt = steinerpt;
+
+          st_facref_count++;
+          if (steinerleft > 0) steinerleft--;
+        } // if (steinerflag)
+      }
+    } else {
+      success = 0;      
+    }
+
+    if (!success) {
+      if (misshlist != NULL) {
+        // Save this subface.
+        misshlist->newindex((void **) &parysh);
+        *parysh = searchsh;
+      }
+    }
+
+  } // while (subfacstack->objects > 0l)
+
+  return 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// getvertexstar()    Return the star of a vertex.                           //
+//                                                                           //
+// If the flag 'fullstar' is set, return the complete star of this vertex.   //
+// Otherwise, only a part of the star which is bounded by facets is returned.// 
+//                                                                           //
+// 'tetlist' returns the list of tets in the star of the vertex 'searchpt'.  //
+// Every tet in 'tetlist' is at the face opposing to 'searchpt'.             //
+//                                                                           //
+// 'vertlist' returns the list of vertices in the star (exclude 'searchpt'). //
+//                                                                           //
+// 'shlist' returns the list of subfaces in the star. Each subface must face //
+// to the interior of this star.                                             //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::getvertexstar(int fullstar, point searchpt, arraypool* tetlist, 
+                              arraypool* vertlist, arraypool* shlist)
+{
+  triface searchtet, neightet, *parytet;
+  face checksh, *parysh;
+  point pt, *parypt;
+  int collectflag;
+  int t1ver;
+  int i, j;
+
+  point2tetorg(searchpt, searchtet);
+
+  // Go to the opposite face (the link face) of the vertex.
+  enextesymself(searchtet);
+  //assert(oppo(searchtet) == searchpt);
+  infect(searchtet); // Collect this tet (link face).
+  tetlist->newindex((void **) &parytet);
+  *parytet = searchtet;
+  if (vertlist != NULL) {
+    // Collect three (link) vertices.
+    j = (searchtet.ver & 3); // The current vertex index.
+    for (i = 1; i < 4; i++) {
+      pt = (point) searchtet.tet[4 + ((j + i) % 4)];
+      pinfect(pt);
+      vertlist->newindex((void **) &parypt);
+      *parypt = pt;
+    }
+  }
+
+  collectflag = 1;
+  esym(searchtet, neightet);
+  if (issubface(neightet)) {
+    if (shlist != NULL) {
+      tspivot(neightet, checksh);
+      if (!sinfected(checksh)) {
+        // Collect this subface (link edge).
+        sinfected(checksh);
+        shlist->newindex((void **) &parysh);
+        *parysh = checksh;
+      }
+    } 
+    if (!fullstar) {
+      collectflag = 0;
+    }
+  }
+  if (collectflag) {
+    fsymself(neightet); // Goto the adj tet of this face.
+    esymself(neightet); // Goto the oppo face of this vertex.
+    // assert(oppo(neightet) == searchpt);
+    infect(neightet); // Collect this tet (link face).
+    tetlist->newindex((void **) &parytet);
+    *parytet = neightet;
+    if (vertlist != NULL) {
+      // Collect its apex.
+      pt = apex(neightet);
+      pinfect(pt);
+      vertlist->newindex((void **) &parypt);
+      *parypt = pt;
+    }
+  } // if (collectflag)
+
+  // Continue to collect all tets in the star.
+  for (i = 0; i < tetlist->objects; i++) {
+    searchtet = * (triface *) fastlookup(tetlist, i);
+    // Note that 'searchtet' is a face opposite to 'searchpt', and the neighbor
+    //   tet at the current edge is already collected.
+    // Check the neighbors at the other two edges of this face.
+    for (j = 0; j < 2; j++) {
+      collectflag = 1;
+      enextself(searchtet);
+      esym(searchtet, neightet);
+      if (issubface(neightet)) {
+        if (shlist != NULL) {
+          tspivot(neightet, checksh);
+          if (!sinfected(checksh)) {
+            // Collect this subface (link edge).
+            sinfected(checksh);
+            shlist->newindex((void **) &parysh);
+            *parysh = checksh;
+          }
+        }
+        if (!fullstar) {
+          collectflag = 0;
+        }
+      }
+      if (collectflag) {
+        fsymself(neightet);
+        if (!infected(neightet)) {
+          esymself(neightet); // Go to the face opposite to 'searchpt'.
+          infect(neightet);
+          tetlist->newindex((void **) &parytet);
+          *parytet = neightet;
+          if (vertlist != NULL) {
+            // Check if a vertex is collected.
+            pt = apex(neightet);
+            if (!pinfected(pt)) {
+              pinfect(pt);
+              vertlist->newindex((void **) &parypt);
+              *parypt = pt;
+            }
+          }
+        } // if (!infected(neightet))
+      } // if (collectflag)
+    } // j
+  } // i
+
+
+  // Uninfect the list of tets and vertices.
+  for (i = 0; i < tetlist->objects; i++) {
+    parytet = (triface *) fastlookup(tetlist, i);
+    uninfect(*parytet);
+  }
+
+  if (vertlist != NULL) {
+    for (i = 0; i < vertlist->objects; i++) {
+      parypt = (point *) fastlookup(vertlist, i);
+      puninfect(*parypt);
+    }
+  }
+
+  if (shlist != NULL) {
+    for (i = 0; i < shlist->objects; i++) {
+      parysh = (face *) fastlookup(shlist, i);
+      suninfect(*parysh);
+    }
+  }
+
+  return (int) tetlist->objects;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// getedge()    Get a tetrahedron having the two endpoints.                  //
+//                                                                           //
+// The method here is to search the second vertex in the link faces of the   //
+// first vertex. The global array 'cavetetlist' is re-used for searching.    //
+//                                                                           //
+// This function is used for the case when the mesh is non-convex. Otherwise,//
+// the function finddirection() should be faster than this.                  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::getedge(point e1, point e2, triface *tedge)
+{
+  triface searchtet, neightet, *parytet;
+  point pt;
+  int done;
+  int i, j;
+
+  if (b->verbose > 2) {
+    printf("      Get edge from %d to %d.\n", pointmark(e1), pointmark(e2));
+  }
+
+  // Quickly check if 'tedge' is just this edge.
+  if (!isdeadtet(*tedge)) {
+    if (org(*tedge) == e1) {
+      if (dest(*tedge) == e2) {
+        return 1;
+      }
+    } else if (org(*tedge) == e2) {
+      if (dest(*tedge) == e1) {
+        esymself(*tedge);
+        return 1;
+      }
+    }
+  }
+
+  // Search for the edge [e1, e2].
+  point2tetorg(e1, *tedge);
+  finddirection(tedge, e2);
+  if (dest(*tedge) == e2) {
+    return 1;
+  } else {
+    // Search for the edge [e2, e1].
+    point2tetorg(e2, *tedge);
+    finddirection(tedge, e1);
+    if (dest(*tedge) == e1) {
+      esymself(*tedge);
+      return 1;
+    }
+  }
+
+
+  // Go to the link face of e1.
+  point2tetorg(e1, searchtet);
+  enextesymself(searchtet);
+  arraypool *tetlist = cavebdrylist;
+
+  // Search e2.
+  for (i = 0; i < 3; i++) {
+    pt = apex(searchtet);
+    if (pt == e2) {
+      // Found. 'searchtet' is [#,#,e2,e1].
+      eorgoppo(searchtet, *tedge); // [e1,e2,#,#].
+      return 1;
+    }
+    enextself(searchtet);
+  }
+
+  // Get the adjacent link face at 'searchtet'.
+  fnext(searchtet, neightet);
+  esymself(neightet);
+  // assert(oppo(neightet) == e1);
+  pt = apex(neightet);
+  if (pt == e2) {
+    // Found. 'neightet' is [#,#,e2,e1].
+    eorgoppo(neightet, *tedge); // [e1,e2,#,#].
+    return 1;
+  }
+
+  // Continue searching in the link face of e1.
+  infect(searchtet);
+  tetlist->newindex((void **) &parytet);
+  *parytet = searchtet;
+  infect(neightet);
+  tetlist->newindex((void **) &parytet);
+  *parytet = neightet;
+
+  done = 0;
+
+  for (i = 0; (i < tetlist->objects) && !done; i++) {
+    parytet = (triface *) fastlookup(tetlist, i);
+    searchtet = *parytet;
+    for (j = 0; (j < 2) && !done; j++) {
+      enextself(searchtet);
+      fnext(searchtet, neightet);
+      if (!infected(neightet)) {        
+        esymself(neightet);
+        pt = apex(neightet);
+        if (pt == e2) {
+          // Found. 'neightet' is [#,#,e2,e1].
+          eorgoppo(neightet, *tedge);
+          done = 1;
+        } else {
+          infect(neightet);
+          tetlist->newindex((void **) &parytet);
+          *parytet = neightet;
+        }
+      }
+    } // j
+  } // i 
+
+  // Uninfect the list of visited tets.
+  for (i = 0; i < tetlist->objects; i++) {
+    parytet = (triface *) fastlookup(tetlist, i);
+    uninfect(*parytet);
+  }
+  tetlist->restart();
+
+  return done;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// reduceedgesatvertex()    Reduce the number of edges at a given vertex.    //
+//                                                                           //
+// 'endptlist' contains the endpoints of edges connecting at the vertex.     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::reduceedgesatvertex(point startpt, arraypool* endptlist)
+{
+  triface searchtet;
+  point *pendpt, *parypt;
+  enum interresult dir;
+  flipconstraints fc;
+  int reduceflag;
+  int count;
+  int n, i, j;
+
+
+  fc.remvert = startpt;
+  fc.checkflipeligibility = 1;
+
+  while (1) {
+
+    count = 0;
+
+    for (i = 0; i < endptlist->objects; i++) {
+      pendpt = (point *) fastlookup(endptlist, i);
+      if (*pendpt == dummypoint) {
+        continue; // Do not reduce a virtual edge.
+      }
+      reduceflag = 0;
+      // Find the edge.
+      if (nonconvex) {
+        if (getedge(startpt, *pendpt, &searchtet)) {
+          dir = ACROSSVERT;
+        } else {
+          // The edge does not exist (was flipped).
+          dir = INTERSECT;
+        }
+      } else {
+        point2tetorg(startpt, searchtet);
+        dir = finddirection(&searchtet, *pendpt);
+      }
+      if (dir == ACROSSVERT) {
+        if (dest(searchtet) == *pendpt) {
+          // Do not flip a segment.
+          if (!issubseg(searchtet)) {
+            n = removeedgebyflips(&searchtet, &fc);
+            if (n == 2) {
+              reduceflag = 1;
+            }
+          }
+        }
+      } else {
+        // The edge has been flipped.
+        reduceflag = 1;
+      }
+      if (reduceflag) {
+        count++;
+        // Move the last vertex into this slot.
+        j = endptlist->objects - 1;
+        parypt = (point *) fastlookup(endptlist, j);
+        *pendpt = *parypt;
+        endptlist->objects--;
+        i--;
+      }
+    } // i
+
+    if (count == 0) {
+      // No edge is reduced.
+      break;
+    }
+
+  } // while (1)
+
+  return (int) endptlist->objects;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// removevertexbyflips()    Remove a vertex by flips.                        //
+//                                                                           //
+// This routine attempts to remove the given vertex 'rempt' (p) from the     //
+// tetrahedralization (T) by a sequence of flips.                            //
+//                                                                           //
+// The algorithm used here is a simple edge reduce method. Suppose there are //
+// n edges connected at p. We try to reduce the number of edges by flipping  //
+// any edge (not a segment) that is connecting at p.                         //
+//                                                                           //
+// Unless T is a Delaunay tetrahedralization, there is no guarantee that 'p' //
+// can be successfully removed.                                              //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::removevertexbyflips(point steinerpt)
+{
+  triface *fliptets = NULL, wrktets[4];
+  triface searchtet, spintet, neightet;
+  face parentsh, spinsh, checksh;
+  face leftseg, rightseg, checkseg;
+  point lpt = NULL, rpt = NULL, apexpt; //, *parypt;
+  flipconstraints fc;
+  enum verttype vt;
+  enum locateresult loc;
+  int valence, removeflag;
+  int slawson;
+  int t1ver;
+  int n, i;
+
+  vt = pointtype(steinerpt);
+
+  if (vt == FREESEGVERTEX) {
+    sdecode(point2sh(steinerpt), leftseg);
+    leftseg.shver = 0;
+    if (sdest(leftseg) == steinerpt) {
+      senext(leftseg, rightseg);
+      spivotself(rightseg);
+      rightseg.shver = 0;
+    } else {
+      rightseg = leftseg;
+      senext2(rightseg, leftseg);
+      spivotself(leftseg);
+      leftseg.shver = 0;
+    }
+    lpt = sorg(leftseg);
+    rpt = sdest(rightseg);
+    if (b->verbose > 2) {
+      printf("      Removing Steiner point %d in segment (%d, %d).\n",
+             pointmark(steinerpt), pointmark(lpt), pointmark(rpt));
+
+    }
+  } else if (vt == FREEFACETVERTEX) {
+    if (b->verbose > 2) {
+      printf("      Removing Steiner point %d in facet.\n",
+             pointmark(steinerpt));
+    }
+  } else if (vt == FREEVOLVERTEX) {
+    if (b->verbose > 2) {
+      printf("      Removing Steiner point %d in volume.\n",
+             pointmark(steinerpt));
+    }
+  } else if (vt == VOLVERTEX) {
+    if (b->verbose > 2) {
+      printf("      Removing a point %d in volume.\n",
+             pointmark(steinerpt));
+    }
+  } else {
+    // It is not a Steiner point.
+    return 0;
+  }
+
+  // Try to reduce the number of edges at 'p' by flips.
+  getvertexstar(1, steinerpt, cavetetlist, cavetetvertlist, NULL);
+  cavetetlist->restart(); // This list may be re-used.
+  if (cavetetvertlist->objects > 3l) {
+    valence = reduceedgesatvertex(steinerpt, cavetetvertlist);
+  } else {
+    valence = cavetetvertlist->objects;
+  }
+  cavetetvertlist->restart();
+
+  removeflag = 0;
+
+  if (valence == 4) {
+    // Only 4 vertices (4 tets) left! 'p' is inside the convex hull of the 4
+    //   vertices. This case is due to that 'p' is not exactly on the segment.
+    point2tetorg(steinerpt, searchtet);
+    loc = INTETRAHEDRON;
+    removeflag = 1;
+  } else if (valence == 5) {
+    // There are 5 edges.
+    if (vt == FREESEGVERTEX) {
+      sstpivot1(leftseg, searchtet);
+      if (org(searchtet) != steinerpt) {
+        esymself(searchtet);
+      }
+      i = 0; // Count the numbe of tet at the edge [p,lpt].
+      neightet.tet = NULL; // Init the face.
+      spintet = searchtet;
+      while (1) {
+        i++;
+        if (apex(spintet) == rpt) {
+          // Remember the face containing the edge [lpt, rpt].
+          neightet = spintet;
+        }
+        fnextself(spintet);
+        if (spintet.tet == searchtet.tet) break;
+      }
+      if (i == 3) {
+        // This case has been checked below.
+      } else if (i == 4) {
+        // There are 4 tets sharing at [p,lpt]. There must be 4 tets sharing
+        //   at [p,rpt].  There must be a face [p, lpt, rpt].  
+        if (apex(neightet) == rpt) {
+          // The edge (segment) has been already recovered!  
+          // Check if a 6-to-2 flip is possible (to remove 'p').
+          // Let 'searchtet' be [p,d,a,b]
+          esym(neightet, searchtet);
+          enextself(searchtet);
+          // Check if there are exactly three tets at edge [p,d].
+          wrktets[0] = searchtet; // [p,d,a,b]
+          for (i = 0; i < 2; i++) {
+            fnext(wrktets[i], wrktets[i+1]); // [p,d,b,c], [p,d,c,a]
+          }
+          if (apex(wrktets[0]) == oppo(wrktets[2])) {
+            loc = ONFACE;
+            removeflag = 1;
+          }
+        }
+      }
+    } else if (vt == FREEFACETVERTEX) {
+      // It is possible to do a 6-to-2 flip to remove the vertex.
+      point2tetorg(steinerpt, searchtet);
+      // Get the three faces of 'searchtet' which share at p.
+      //    All faces has p as origin.
+      wrktets[0] = searchtet;
+      wrktets[1] = searchtet;
+      esymself(wrktets[1]);
+      enextself(wrktets[1]);
+      wrktets[2] = searchtet;
+      eprevself(wrktets[2]);
+      esymself(wrktets[2]);
+      // All internal edges of the six tets have valance either 3 or 4.
+      // Get one edge which has valance 3.
+      searchtet.tet = NULL;
+      for (i = 0; i < 3; i++) {
+        spintet = wrktets[i];
+        valence = 0;
+        while (1) {
+          valence++;
+          fnextself(spintet);
+          if (spintet.tet == wrktets[i].tet) break;
+        }
+        if (valence == 3) {
+          // Found the edge.
+          searchtet = wrktets[i];
+          break;
+        }
+      }
+      // Note, we do not detach the three subfaces at p.
+      // They will be removed within a 4-to-1 flip.
+      loc = ONFACE;
+      removeflag = 1;
+    }
+    //removeflag = 1;
+  } 
+
+  if (!removeflag) {
+    if (vt == FREESEGVERTEX) { 
+      // Check is it possible to recover the edge [lpt,rpt].
+      // The condition to check is:  Whether each tet containing 'leftseg' is
+      //   adjacent to a tet containing 'rightseg'.
+      sstpivot1(leftseg, searchtet);
+      if (org(searchtet) != steinerpt) {
+        esymself(searchtet);
+      }
+      spintet = searchtet;
+      while (1) {
+        // Go to the bottom face of this tet.
+        eprev(spintet, neightet);
+        esymself(neightet);  // [steinerpt, p1, p2, lpt]
+        // Get the adjacent tet.
+        fsymself(neightet);  // [p1, steinerpt, p2, rpt]
+        if (oppo(neightet) != rpt) {
+          // Found a non-matching adjacent tet.
+          break;
+        }
+        fnextself(spintet);
+        if (spintet.tet == searchtet.tet) {
+          // 'searchtet' is [p,d,p1,p2].
+          loc = ONEDGE;
+          removeflag = 1;
+          break;
+        }
+      }
+    } // if (vt == FREESEGVERTEX)
+  }
+
+  if (!removeflag) {
+    if (vt == FREESEGVERTEX) {
+      // Check if the edge [lpt, rpt] exists.
+      if (getedge(lpt, rpt, &searchtet)) {
+        // We have recovered this edge. Shift the vertex into the volume.
+        // We can recover this edge if the subfaces are not recovered yet.
+        if (!checksubfaceflag) {
+          // Remove the vertex from the surface mesh.
+          //   This will re-create the segment [lpt, rpt] and re-triangulate
+          //   all the facets at the segment.
+          // Detach the subsegments from their surrounding tets.
+          for (i = 0; i < 2; i++) {
+            checkseg = (i == 0) ? leftseg : rightseg;
+            sstpivot1(checkseg, neightet);
+            spintet = neightet;
+            while (1) {
+              tssdissolve1(spintet);
+              fnextself(spintet);
+              if (spintet.tet == neightet.tet) break;
+            }
+            sstdissolve1(checkseg);
+          } // i
+          slawson = 1; // Do lawson flip after removal.
+          spivot(rightseg, parentsh); // 'rightseg' has p as its origin.
+          sremovevertex(steinerpt, &parentsh, &rightseg, slawson);
+          // Clear the list for new subfaces.
+          caveshbdlist->restart();
+          // Insert the new segment.
+          sstbond1(rightseg, searchtet);
+          spintet = searchtet;
+          while (1) {
+            tssbond1(spintet, rightseg);
+            fnextself(spintet);
+            if (spintet.tet == searchtet.tet) break;
+          }
+          // The Steiner point has been shifted into the volume.
+          setpointtype(steinerpt, FREEVOLVERTEX);          
+          st_segref_count--;
+          st_volref_count++;
+          return 1;
+        } // if (!checksubfaceflag)
+      } // if (getedge(...))
+    } // if (vt == FREESEGVERTEX)
+  } // if (!removeflag)
+
+  if (!removeflag) {
+    return 0;
+  }
+
+  if (vt == FREESEGVERTEX) {
+    // Detach the subsegments from their surronding tets.
+    for (i = 0; i < 2; i++) {
+      checkseg = (i == 0) ? leftseg : rightseg;
+      sstpivot1(checkseg, neightet);
+      spintet = neightet;
+      while (1) {
+        tssdissolve1(spintet);
+        fnextself(spintet);
+        if (spintet.tet == neightet.tet) break;
+      }
+      sstdissolve1(checkseg);
+    } // i
+    if (checksubfaceflag) {
+      // Detach the subfaces at the subsegments from their attached tets.
+      for (i = 0; i < 2; i++) {
+        checkseg = (i == 0) ? leftseg : rightseg;
+        spivot(checkseg, parentsh);
+        if (parentsh.sh != NULL) {
+          spinsh = parentsh;
+          while (1) {
+            stpivot(spinsh, neightet);
+            if (neightet.tet != NULL) {
+              tsdissolve(neightet);
+            }
+            sesymself(spinsh);
+            stpivot(spinsh, neightet);
+            if (neightet.tet != NULL) {
+              tsdissolve(neightet);
+            }
+            stdissolve(spinsh);
+            spivotself(spinsh); // Go to the next subface.
+            if (spinsh.sh == parentsh.sh) break;
+          }
+        }
+      } // i
+    } // if (checksubfaceflag)
+  }
+
+  if (loc == INTETRAHEDRON) {
+    // Collect the four tets containing 'p'.
+    fliptets = new triface[4];
+    fliptets[0] = searchtet; // [p,d,a,b]
+    for (i = 0; i < 2; i++) {
+      fnext(fliptets[i], fliptets[i+1]); // [p,d,b,c], [p,d,c,a]
+    }
+    eprev(fliptets[0], fliptets[3]);
+    fnextself(fliptets[3]); // it is [a,p,b,c]
+    eprevself(fliptets[3]);
+    esymself(fliptets[3]); // [a,b,c,p].
+    // Remove p by a 4-to-1 flip.
+    //flip41(fliptets, 1, 0, 0);
+    flip41(fliptets, 1, &fc);
+    //recenttet = fliptets[0];
+  } else if (loc == ONFACE) {
+    // Let the original two tets be [a,b,c,d] and [b,a,c,e]. And p is in
+    //   face [a,b,c].  Let 'searchtet' be the tet [p,d,a,b].
+    // Collect the six tets containing 'p'.
+    fliptets = new triface[6];
+    fliptets[0] = searchtet; // [p,d,a,b]
+    for (i = 0; i < 2; i++) {
+      fnext(fliptets[i], fliptets[i+1]); // [p,d,b,c], [p,d,c,a]
+    }
+    eprev(fliptets[0], fliptets[3]);
+    fnextself(fliptets[3]); // [a,p,b,e]
+    esymself(fliptets[3]);  // [p,a,e,b]
+    eprevself(fliptets[3]); // [e,p,a,b]
+    for (i = 3; i < 5; i++) {
+      fnext(fliptets[i], fliptets[i+1]); // [e,p,b,c], [e,p,c,a]
+    }
+    if (vt == FREEFACETVERTEX) {
+      // We need to determine the location of three subfaces at p.
+      valence = 0; // Re-use it.
+      // Check if subfaces are all located in the lower three tets.
+      //   i.e., [e,p,a,b], [e,p,b,c], and [e,p,c,a].
+      for (i = 3; i < 6; i++) {
+        if (issubface(fliptets[i])) valence++;
+      }
+      if (valence > 0) {
+        // We must do 3-to-2 flip in the upper part. We simply re-arrange
+        //   the six tets.
+        for (i = 0; i < 3; i++) {
+          esym(fliptets[i+3], wrktets[i]);
+          esym(fliptets[i], fliptets[i+3]);
+          fliptets[i] = wrktets[i];
+        }
+        // Swap the last two pairs, i.e., [1]<->[[2], and [4]<->[5]
+        wrktets[1] = fliptets[1];
+        fliptets[1] = fliptets[2];
+        fliptets[2] = wrktets[1];
+        wrktets[1] = fliptets[4];
+        fliptets[4] = fliptets[5];
+        fliptets[5] = wrktets[1];
+      }
+    }
+    // Remove p by a 6-to-2 flip, which is a combination of two flips:
+    //   a 3-to-2 (deletes the edge [e,p]), and
+    //   a 4-to-1 (deletes the vertex p).
+    // First do a 3-to-2 flip on [e,p,a,b],[e,p,b,c],[e,p,c,a]. It creates
+    //   two new tets: [a,b,c,p] and [b,a,c,e].  The new tet [a,b,c,p] is
+    //   degenerate (has zero volume). It will be deleted in the followed
+    //   4-to-1 flip.
+    //flip32(&(fliptets[3]), 1, 0, 0);
+    flip32(&(fliptets[3]), 1, &fc);
+    // Second do a 4-to-1 flip on [p,d,a,b],[p,d,b,c],[p,d,c,a],[a,b,c,p].
+    //   This creates a new tet [a,b,c,d].
+    //flip41(fliptets, 1, 0, 0);
+    flip41(fliptets, 1, &fc);
+    //recenttet = fliptets[0];
+  } else if (loc == ONEDGE) {
+    // Let the original edge be [e,d] and p is in [e,d]. Assume there are n
+    //   tets sharing at edge [e,d] originally.  We number the link vertices
+    //   of [e,d]: p_0, p_1, ..., p_n-1. 'searchtet' is [p,d,p_0,p_1].
+    // Count the number of tets at edge [e,p] and [p,d] (this is n).
+    n = 0;
+    spintet = searchtet;
+    while (1) {
+      n++;
+      fnextself(spintet);
+      if (spintet.tet == searchtet.tet) break;
+    }
+    // Collect the 2n tets containing 'p'.
+    fliptets = new triface[2 * n];
+    fliptets[0] = searchtet; // [p,b,p_0,p_1] 
+    for (i = 0; i < (n - 1); i++) {
+      fnext(fliptets[i], fliptets[i+1]); // [p,d,p_i,p_i+1].
+    }
+    eprev(fliptets[0], fliptets[n]);
+    fnextself(fliptets[n]); // [p_0,p,p_1,e]
+    esymself(fliptets[n]);  // [p,p_0,e,p_1]
+    eprevself(fliptets[n]); // [e,p,p_0,p_1]
+    for (i = n; i <  (2 * n - 1); i++) {
+      fnext(fliptets[i], fliptets[i+1]); // [e,p,p_i,p_i+1].
+    }
+    // Remove p by a 2n-to-n flip, it is a sequence of n flips:
+    // - Do a 2-to-3 flip on 
+    //     [p_0,p_1,p,d] and 
+    //     [p,p_1,p_0,e].
+    //   This produces: 
+    //     [e,d,p_0,p_1], 
+    //     [e,d,p_1,p] (degenerated), and 
+    //     [e,d,p,p_0] (degenerated).
+    wrktets[0] = fliptets[0]; // [p,d,p_0,p_1]
+    eprevself(wrktets[0]);    // [p_0,p,d,p_1]
+    esymself(wrktets[0]);     // [p,p_0,p_1,d]
+    enextself(wrktets[0]);    // [p_0,p_1,p,d] [0]
+    wrktets[1] = fliptets[n]; // [e,p,p_0,p_1]
+    enextself(wrktets[1]);    // [p,p_0,e,p_1]
+    esymself(wrktets[1]);     // [p_0,p,p_1,e]
+    eprevself(wrktets[1]);    // [p_1,p_0,p,e] [1]
+    //flip23(wrktets, 1, 0, 0);
+    flip23(wrktets, 1, &fc);
+    // Save the new tet [e,d,p,p_0] (degenerated).
+    fliptets[n] = wrktets[2];
+    // Save the new tet [e,d,p_0,p_1].
+    fliptets[0] = wrktets[0];
+    // - Repeat from i = 1 to n-2: (n - 2) flips
+    //   - Do a 3-to-2 flip on 
+    //       [p,p_i,d,e], 
+    //       [p,p_i,e,p_i+1], and 
+    //       [p,p_i,p_i+1,d]. 
+    //     This produces: 
+    //       [d,e,p_i+1,p_i], and
+    //       [e,d,p_i+1,p] (degenerated).
+    for (i = 1; i < (n - 1); i++) {
+      wrktets[0] = wrktets[1]; // [e,d,p_i,p] (degenerated).
+      enextself(wrktets[0]);   // [d,p_i,e,p] (...)
+      esymself(wrktets[0]);    // [p_i,d,p,e] (...) 
+      eprevself(wrktets[0]);   // [p,p_i,d,e] (degenerated) [0].
+      wrktets[1] = fliptets[n+i];  // [e,p,p_i,p_i+1]
+      enextself(wrktets[1]);       // [p,p_i,e,p_i+1] [1]
+      wrktets[2] = fliptets[i]; // [p,d,p_i,p_i+1]
+      eprevself(wrktets[2]);    // [p_i,p,d,p_i+1]
+      esymself(wrktets[2]);     // [p,p_i,p_i+1,d] [2]
+      //flip32(wrktets, 1, 0, 0);
+      flip32(wrktets, 1, &fc);
+      // Save the new tet [e,d,p_i,p_i+1].         // FOR DEBUG ONLY
+      fliptets[i] = wrktets[0]; // [d,e,p_i+1,p_i] // FOR DEBUG ONLY
+      esymself(fliptets[i]);    // [e,d,p_i,p_i+1] // FOR DEBUG ONLY
+    }
+    // - Do a 4-to-1 flip on 
+    //     [p,p_0,e,d],     [d,e,p_0,p],
+    //     [p,p_0,d,p_n-1], [e,p_n-1,p_0,p], 
+    //     [p,p_0,p_n-1,e], [p_0,p_n-1,d,p], and
+    //     [e,d,p_n-1,p]. 
+    //   This produces 
+    //     [e,d,p_n-1,p_0] and 
+    //     deletes p.
+    wrktets[3] = wrktets[1];  // [e,d,p_n-1,p] (degenerated) [3]
+    wrktets[0] = fliptets[n]; // [e,d,p,p_0] (degenerated)
+    eprevself(wrktets[0]);    // [p,e,d,p_0] (...)
+    esymself(wrktets[0]);     // [e,p,p_0,d] (...)
+    enextself(wrktets[0]);    // [p,p_0,e,d] (degenerated) [0]
+    wrktets[1] = fliptets[n-1];   // [p,d,p_n-1,p_0]
+    esymself(wrktets[1]);         // [d,p,p_0,p_n-1]
+    enextself(wrktets[1]);        // [p,p_0,d,p_n-1] [1]
+    wrktets[2] = fliptets[2*n-1]; // [e,p,p_n-1,p_0]
+    enextself(wrktets[2]);        // [p_p_n-1,e,p_0]
+    esymself(wrktets[2]);         // [p_n-1,p,p_0,e]
+    enextself(wrktets[2]);        // [p,p_0,p_n-1,e] [2]
+    //flip41(wrktets, 1, 0, 0);
+    flip41(wrktets, 1, &fc);
+    // Save the new tet [e,d,p_n-1,p_0]             // FOR DEBUG ONLY
+    fliptets[n-1] = wrktets[0];  // [e,d,p_n-1,p_0] // FOR DEBUG ONLY
+    //recenttet = fliptets[0];
+  }
+
+  delete [] fliptets;
+
+  if (vt == FREESEGVERTEX) {
+    // Remove the vertex from the surface mesh.
+    //   This will re-create the segment [lpt, rpt] and re-triangulate
+    //   all the facets at the segment.
+    // Only do lawson flip when subfaces are not recovery yet.
+    slawson = (checksubfaceflag ? 0 : 1);
+    spivot(rightseg, parentsh); // 'rightseg' has p as its origin.
+    sremovevertex(steinerpt, &parentsh, &rightseg, slawson);
+
+    // The original segment is returned in 'rightseg'. 
+    rightseg.shver = 0;
+    // Insert the new segment.
+    point2tetorg(lpt, searchtet);
+    finddirection(&searchtet, rpt);
+    sstbond1(rightseg, searchtet);
+    spintet = searchtet;
+    while (1) {
+      tssbond1(spintet, rightseg);
+      fnextself(spintet);
+      if (spintet.tet == searchtet.tet) break;
+    }
+
+    if (checksubfaceflag) {
+      // Insert subfaces at segment [lpt,rpt] into the tetrahedralization.
+      spivot(rightseg, parentsh);
+      if (parentsh.sh != NULL) {
+        spinsh = parentsh;
+        while (1) {
+          if (sorg(spinsh) != lpt) {
+            sesymself(spinsh);
+          }
+          apexpt = sapex(spinsh);
+          // Find the adjacent tet of [lpt,rpt,apexpt];
+          spintet = searchtet;
+          while (1) {
+            if (apex(spintet) == apexpt) {
+              tsbond(spintet, spinsh);
+              sesymself(spinsh); // Get to another side of this face.
+              fsym(spintet, neightet);
+              tsbond(neightet, spinsh);
+              sesymself(spinsh); // Get back to the original side.
+              break;
+            }
+            fnextself(spintet);
+          }
+          spivotself(spinsh);
+          if (spinsh.sh == parentsh.sh) break;
+        }
+      }
+    } // if (checksubfaceflag)
+
+    // Clear the set of new subfaces.
+    caveshbdlist->restart();
+  } // if (vt == FREESEGVERTEX)
+
+  // The point has been removed.
+  if (pointtype(steinerpt) != UNUSEDVERTEX) {
+    setpointtype(steinerpt, UNUSEDVERTEX);
+    unuverts++;
+  }
+  if (vt != VOLVERTEX) {
+    // Update the correspinding counters.
+    if (vt == FREESEGVERTEX) {
+      st_segref_count--;
+    } else if (vt == FREEFACETVERTEX) {
+      st_facref_count--;
+    } else if (vt == FREEVOLVERTEX) {
+      st_volref_count--;
+    }
+    if (steinerleft > 0) steinerleft++;
+  }
+
+  return 1;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// suppressbdrysteinerpoint()    Suppress a boundary Steiner point           //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::suppressbdrysteinerpoint(point steinerpt)
+{
+  face parentsh, spinsh, *parysh;
+  face leftseg, rightseg;
+  point lpt = NULL, rpt = NULL;
+  int i;
+
+  verttype vt = pointtype(steinerpt);
+
+  if (vt == FREESEGVERTEX) {
+    sdecode(point2sh(steinerpt), leftseg);
+    leftseg.shver = 0;
+    if (sdest(leftseg) == steinerpt) {
+      senext(leftseg, rightseg);
+      spivotself(rightseg);
+      rightseg.shver = 0;
+    } else {
+      rightseg = leftseg;
+      senext2(rightseg, leftseg);
+      spivotself(leftseg);
+      leftseg.shver = 0;
+    }
+    lpt = sorg(leftseg);
+    rpt = sdest(rightseg);
+    if (b->verbose > 2) {
+      printf("      Suppressing Steiner point %d in segment (%d, %d).\n",
+             pointmark(steinerpt), pointmark(lpt), pointmark(rpt));
+    }
+    // Get all subfaces at the left segment [lpt, steinerpt].
+    spivot(leftseg, parentsh);
+    if (parentsh.sh != NULL) {
+      // It is not a dangling segment.
+      spinsh = parentsh;
+      while (1) {
+        cavesegshlist->newindex((void **) &parysh);
+        *parysh = spinsh;
+        // Orient the face consistently. 
+        if (sorg(*parysh)!= sorg(parentsh)) sesymself(*parysh);
+        spivotself(spinsh);
+        if (spinsh.sh == NULL) break;
+        if (spinsh.sh == parentsh.sh) break;
+      }
+    }
+    if (cavesegshlist->objects < 2) {
+      // It is a single segment. Not handle it yet.
+      cavesegshlist->restart();
+      return 0;
+    }
+  } else if (vt == FREEFACETVERTEX) {
+    if (b->verbose > 2) {
+      printf("      Suppressing Steiner point %d from facet.\n",
+             pointmark(steinerpt));
+    }
+    sdecode(point2sh(steinerpt), parentsh);
+    // A facet Steiner point. There are exactly two sectors.
+    for (i = 0; i < 2; i++) {
+      cavesegshlist->newindex((void **) &parysh);
+      *parysh = parentsh;
+      sesymself(parentsh);
+    }
+  } else {
+    return 0;
+  }
+
+  triface searchtet, neightet, *parytet;
+  point pa, pb, pc, pd;
+  REAL v1[3], v2[3], len, u;
+
+  REAL startpt[3] = {0,}, samplept[3] = {0,}, candpt[3] = {0,};
+  REAL ori, minvol, smallvol;
+  int samplesize;
+  int it, j, k;
+
+  int n = (int) cavesegshlist->objects;
+  point *newsteiners = new point[n];
+  for (i = 0; i < n; i++) newsteiners[i] = NULL;
+
+  // Search for each sector an interior vertex. 
+  for (i = 0; i < cavesegshlist->objects; i++) {
+    parysh = (face *) fastlookup(cavesegshlist, i);
+    stpivot(*parysh, searchtet);
+    // Skip it if it is outside.
+    if (ishulltet(searchtet)) continue;
+    // Get the "half-ball". Tets in 'cavetetlist' all contain 'steinerpt' as
+    //   opposite.  Subfaces in 'caveshlist' all contain 'steinerpt' as apex.
+    //   Moreover, subfaces are oriented towards the interior of the ball.
+    setpoint2tet(steinerpt, encode(searchtet));
+    getvertexstar(0, steinerpt, cavetetlist, NULL, caveshlist);
+    // Calculate the searching vector.
+    pa = sorg(*parysh);
+    pb = sdest(*parysh);
+    pc = sapex(*parysh);
+    facenormal(pa, pb, pc, v1, 1, NULL);
+    len = sqrt(dot(v1, v1));
+    v1[0] /= len;
+    v1[1] /= len;
+    v1[2] /= len;
+    if (vt == FREESEGVERTEX) {
+      parysh = (face *) fastlookup(cavesegshlist, (i + 1) % n);
+      pd = sapex(*parysh);
+      facenormal(pb, pa, pd, v2, 1, NULL);
+      len = sqrt(dot(v2, v2));
+      v2[0] /= len;
+      v2[1] /= len;
+      v2[2] /= len;
+      // Average the two vectors.
+      v1[0] = 0.5 * (v1[0] + v2[0]);
+      v1[1] = 0.5 * (v1[1] + v2[1]);
+      v1[2] = 0.5 * (v1[2] + v2[2]);
+    }
+    // Search the intersection of the ray starting from 'steinerpt' to
+    //   the search direction 'v1' and the shell of the half-ball.
+    // - Construct an endpoint.
+    len = distance(pa, pb);
+    v2[0] = steinerpt[0] + len * v1[0];
+    v2[1] = steinerpt[1] + len * v1[1];
+    v2[2] = steinerpt[2] + len * v1[2];
+    for (j = 0; j < cavetetlist->objects; j++) {
+      parytet = (triface *) fastlookup(cavetetlist, j);
+      pa = org(*parytet);
+      pb = dest(*parytet);
+      pc = apex(*parytet);
+      // Test if the ray startpt->v2 lies in the cone: where 'steinerpt'
+      //   is the apex, and three sides are defined by the triangle 
+      //   [pa, pb, pc].
+      ori = orient3d(steinerpt, pa, pb, v2);
+      if (ori >= 0) {
+        ori = orient3d(steinerpt, pb, pc, v2);
+        if (ori >= 0) {
+          ori = orient3d(steinerpt, pc, pa, v2);
+          if (ori >= 0) {
+            // Found! Calculate the intersection.
+            planelineint(pa, pb, pc, steinerpt, v2, startpt, &u);
+            break;
+          }
+        }
+      }
+    } // j
+    // Close the ball by adding the subfaces.
+    for (j = 0; j < caveshlist->objects; j++) {
+      parysh = (face *) fastlookup(caveshlist, j);
+      stpivot(*parysh, neightet);
+      cavetetlist->newindex((void **) &parytet);
+      *parytet = neightet;
+    }
+    // Search a best point inside the segment [startpt, steinerpt].
+    it = 0;
+    samplesize = 100;
+    v1[0] = steinerpt[0] - startpt[0];
+    v1[1] = steinerpt[1] - startpt[1];
+    v1[2] = steinerpt[2] - startpt[2];
+    minvol = -1.0;
+    while (it < 3) {
+      for (j = 1; j < samplesize - 1; j++) {
+        samplept[0] = startpt[0] + ((REAL) j / (REAL) samplesize) * v1[0];
+        samplept[1] = startpt[1] + ((REAL) j / (REAL) samplesize) * v1[1];
+        samplept[2] = startpt[2] + ((REAL) j / (REAL) samplesize) * v1[2];
+        // Find the minimum volume for 'samplept'.
+        smallvol = -1;
+        for (k = 0; k < cavetetlist->objects; k++) {
+          parytet = (triface *) fastlookup(cavetetlist, k);
+          pa = org(*parytet);
+          pb = dest(*parytet);
+          pc = apex(*parytet);
+          ori = orient3d(pb, pa, pc, samplept);
+          if (ori <= 0) {
+            break; // An invalid tet.
+          }
+          if (smallvol == -1) {
+            smallvol = ori;
+          } else {
+            if (ori < smallvol) smallvol = ori;
+          }
+        } // k
+        if (k == cavetetlist->objects) {
+          // Found a valid point. Remember it.
+          if (minvol == -1.0) {
+            candpt[0] = samplept[0];
+            candpt[1] = samplept[1];
+            candpt[2] = samplept[2];
+            minvol = smallvol;
+          } else {
+            if (minvol < smallvol) {
+              // It is a better location. Remember it.
+              candpt[0] = samplept[0];
+              candpt[1] = samplept[1];
+              candpt[2] = samplept[2];
+              minvol = smallvol;
+            } else {
+              // No improvement of smallest volume. 
+              // Since we are searching along the line [startpt, steinerpy],
+              // The smallest volume can only be decreased later.
+              break;
+            }
+          }
+        }
+      } // j
+      if (minvol > 0) break; 
+      samplesize *= 10;
+      it++;
+    } // while (it < 3)
+    if (minvol == -1.0) {
+      // Failed to find a valid point.
+      cavetetlist->restart();
+      caveshlist->restart();
+      break;
+    }
+    // Create a new Steiner point inside this section.
+    makepoint(&(newsteiners[i]), FREEVOLVERTEX);
+    newsteiners[i][0] = candpt[0];
+    newsteiners[i][1] = candpt[1];
+    newsteiners[i][2] = candpt[2];
+    cavetetlist->restart();
+    caveshlist->restart();
+  } // i
+
+  if (i < cavesegshlist->objects) {
+    // Failed to suppress the vertex.
+    for (; i > 0; i--) {
+      if (newsteiners[i - 1] != NULL) {
+        pointdealloc(newsteiners[i - 1]);
+      }
+    }
+    delete [] newsteiners;
+    cavesegshlist->restart();
+    return 0;
+  }
+
+  // Remove p from the segment or the facet.
+  triface newtet, newface, spintet;
+  face newsh, neighsh;
+  face *splitseg, checkseg;
+  int slawson = 0; // Do not do flip afterword.
+  int t1ver;
+
+  if (vt == FREESEGVERTEX) {
+    // Detach 'leftseg' and 'rightseg' from their adjacent tets.
+    //   These two subsegments will be deleted. 
+    sstpivot1(leftseg, neightet);
+    spintet = neightet;
+    while (1) {
+      tssdissolve1(spintet);
+      fnextself(spintet);
+      if (spintet.tet == neightet.tet) break;
+    }
+    sstpivot1(rightseg, neightet);
+    spintet = neightet;
+    while (1) {
+      tssdissolve1(spintet);
+      fnextself(spintet);
+      if (spintet.tet == neightet.tet) break;
+    }
+  }
+
+  // Loop through all sectors bounded by facets at this segment.
+  //   Within each sector, create a new Steiner point 'np', and replace 'p'
+  //   by 'np' for all tets in this sector.
+  for (i = 0; i < cavesegshlist->objects; i++) {
+    parysh = (face *) fastlookup(cavesegshlist, i);
+    // 'parysh' is the face [lpt, steinerpt, #].
+    stpivot(*parysh, neightet);
+    // Get all tets in this sector.
+    setpoint2tet(steinerpt, encode(neightet));
+    getvertexstar(0, steinerpt, cavetetlist, NULL, caveshlist);
+    if (!ishulltet(neightet)) {
+      // Within each tet in the ball, replace 'p' by 'np'.
+      for (j = 0; j < cavetetlist->objects; j++) {
+        parytet = (triface *) fastlookup(cavetetlist, j);
+        setoppo(*parytet, newsteiners[i]);
+      } // j
+      // Point to a parent tet.
+      parytet = (triface *) fastlookup(cavetetlist, 0);
+      setpoint2tet(newsteiners[i], (tetrahedron) (parytet->tet)); 
+      st_volref_count++;
+      if (steinerleft > 0) steinerleft--;
+    }
+    // Disconnect the set of boundary faces. They're temporarily open faces.
+    //   They will be connected to the new tets after 'p' is removed.
+    for (j = 0; j < caveshlist->objects; j++) {
+      // Get a boundary face.
+      parysh = (face *) fastlookup(caveshlist, j);
+      stpivot(*parysh, neightet);
+      //assert(apex(neightet) == newpt);
+      // Clear the connection at this face.
+      dissolve(neightet);
+      tsdissolve(neightet);
+    }
+    // Clear the working lists.
+    cavetetlist->restart();
+    caveshlist->restart();
+  } // i
+  cavesegshlist->restart();
+
+  if (vt == FREESEGVERTEX) { 
+    spivot(rightseg, parentsh); // 'rightseg' has p as its origin.
+    splitseg = &rightseg;
+  } else {
+    if (sdest(parentsh) == steinerpt) {
+      senextself(parentsh);
+    } else if (sapex(parentsh) == steinerpt) {
+      senext2self(parentsh);
+    }
+    splitseg = NULL;
+  }
+  sremovevertex(steinerpt, &parentsh, splitseg, slawson);
+
+  if (vt == FREESEGVERTEX) {
+    // The original segment is returned in 'rightseg'. 
+    rightseg.shver = 0;
+  }
+
+  // For each new subface, create two new tets at each side of it.
+  //   Both of the two new tets have its opposite be dummypoint. 
+  for (i = 0; i < caveshbdlist->objects; i++) {
+    parysh = (face *) fastlookup(caveshbdlist, i);
+    sinfect(*parysh); // Mark it for connecting new tets.
+    newsh = *parysh;
+    pa = sorg(newsh);
+    pb = sdest(newsh);
+    pc = sapex(newsh);
+    maketetrahedron(&newtet);
+    maketetrahedron(&neightet);
+    setvertices(newtet, pa, pb, pc, dummypoint);
+    setvertices(neightet, pb, pa, pc, dummypoint);
+    bond(newtet, neightet);
+    tsbond(newtet, newsh);
+    sesymself(newsh);
+    tsbond(neightet, newsh);
+  }
+  // Temporarily increase the hullsize.
+  hullsize += (caveshbdlist->objects * 2l);
+
+  if (vt == FREESEGVERTEX) {
+    // Connecting new tets at the recovered segment.
+    spivot(rightseg, parentsh);
+    spinsh = parentsh;
+    while (1) {
+      if (sorg(spinsh) != lpt) sesymself(spinsh);
+      // Get the new tet at this subface.
+      stpivot(spinsh, newtet);
+      tssbond1(newtet, rightseg);
+      // Go to the other face at this segment.
+      spivot(spinsh, neighsh);
+      if (sorg(neighsh) != lpt) sesymself(neighsh);
+      sesymself(neighsh);
+      stpivot(neighsh, neightet);
+      tssbond1(neightet, rightseg);
+      sstbond1(rightseg, neightet); 
+      // Connecting two adjacent tets at this segment.
+      esymself(newtet);
+      esymself(neightet);
+      // Connect the two tets (at rightseg) together.
+      bond(newtet, neightet);
+      // Go to the next subface.
+      spivotself(spinsh);
+      if (spinsh.sh == parentsh.sh) break;
+    }
+  }
+
+  // Connecting new tets at new subfaces together.
+  for (i = 0; i < caveshbdlist->objects; i++) {
+    parysh = (face *) fastlookup(caveshbdlist, i);
+    newsh = *parysh;
+    //assert(sinfected(newsh));
+    // Each new subface contains two new tets.
+    for (k = 0; k < 2; k++) {
+      stpivot(newsh, newtet);
+      for (j = 0; j < 3; j++) {
+        // Check if this side is open.
+        esym(newtet, newface);
+        if (newface.tet[newface.ver & 3] == NULL) {
+          // An open face. Connect it to its adjacent tet.
+          sspivot(newsh, checkseg);
+          if (checkseg.sh != NULL) {
+            // A segment. It must not be the recovered segment.
+            tssbond1(newtet, checkseg);
+            sstbond1(checkseg, newtet);
+          }
+          spivot(newsh, neighsh);
+          if (neighsh.sh != NULL) {
+            // The adjacent subface exists. It's not a dangling segment.
+            if (sorg(neighsh) != sdest(newsh)) sesymself(neighsh);
+            stpivot(neighsh, neightet);
+            if (sinfected(neighsh)) {
+              esymself(neightet);
+            } else {
+              // Search for an open face at this edge.
+              spintet = neightet;
+              while (1) {
+                esym(spintet, searchtet);
+                fsym(searchtet, spintet);
+                if (spintet.tet == NULL) break;
+              }
+              // Found an open face at 'searchtet'.
+              neightet = searchtet;
+            }
+          } else {
+            // The edge (at 'newsh') is a dangling segment.
+            // Get an adjacent tet at this segment.
+            sstpivot1(checkseg, neightet);
+            if (org(neightet) != sdest(newsh)) esymself(neightet);
+            // Search for an open face at this edge.
+            spintet = neightet;
+            while (1) {
+              esym(spintet, searchtet);
+              fsym(searchtet, spintet);
+              if (spintet.tet == NULL) break;
+            }
+            // Found an open face at 'searchtet'.
+            neightet = searchtet;
+          }
+          pc = apex(newface);
+          if (apex(neightet) == steinerpt) {
+            // Exterior case. The 'neightet' is a hull tet which contain
+            //   'steinerpt'. It will be deleted after 'steinerpt' is removed. 
+            caveoldtetlist->newindex((void **) &parytet);
+            *parytet = neightet;
+            // Connect newface to the adjacent hull tet of 'neightet', which
+            //   has the same edge as 'newface', and does not has 'steinerpt'.
+            fnextself(neightet);
+          } else {
+            if (pc == dummypoint) {
+              if (apex(neightet) != dummypoint) {
+                setapex(newface, apex(neightet));
+                // A hull tet has turned into an interior tet.
+                hullsize--; // Must update the hullsize.
+              } 
+            }
+          }
+          bond(newface, neightet);
+        } // if (newface.tet[newface.ver & 3] == NULL)
+        enextself(newtet);
+        senextself(newsh);
+      } // j
+      sesymself(newsh);
+    } // k
+  } // i
+
+  // Unmark all new subfaces.
+  for (i = 0; i < caveshbdlist->objects; i++) {
+    parysh = (face *) fastlookup(caveshbdlist, i);
+    suninfect(*parysh);
+  }
+  caveshbdlist->restart();
+
+  if (caveoldtetlist->objects > 0l) {
+    // Delete hull tets which contain 'steinerpt'.
+    for (i = 0; i < caveoldtetlist->objects; i++) {
+      parytet = (triface *) fastlookup(caveoldtetlist, i);
+      tetrahedrondealloc(parytet->tet);
+    }
+    // Must update the hullsize.
+    hullsize -= caveoldtetlist->objects;
+    caveoldtetlist->restart();
+  }
+
+  setpointtype(steinerpt, UNUSEDVERTEX);
+  unuverts++;
+  if (vt == FREESEGVERTEX) {
+    st_segref_count--;
+  } else { // vt == FREEFACETVERTEX
+    st_facref_count--;
+  }
+  if (steinerleft > 0) steinerleft++;  // We've removed a Steiner points.
+
+
+  point *parypt;
+  int steinercount = 0;
+
+  int bak_fliplinklevel = b->fliplinklevel;
+  b->fliplinklevel = 100000; // Unlimited flip level.
+
+  // Try to remove newly added Steiner points.
+  for (i = 0; i < n; i++) {
+    if (newsteiners[i] != NULL) {
+      if (!removevertexbyflips(newsteiners[i])) {
+        if (b->supsteiner_level > 0) { // Not -Y/0
+          // Save it in subvertstack for removal.
+          subvertstack->newindex((void **) &parypt);
+          *parypt = newsteiners[i];
+        }
+        steinercount++;
+      }
+    }
+  }
+
+  b->fliplinklevel = bak_fliplinklevel;
+
+  if (steinercount > 0) {
+    if (b->verbose > 2) {
+      printf("      Added %d interior Steiner points.\n", steinercount);
+    }
+  }
+
+  delete [] newsteiners;
+
+  return 1;
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// suppresssteinerpoints()    Suppress Steiner points.                       //
+//                                                                           //
+// All Steiner points have been saved in 'subvertstack' in the routines      //
+// carveholes() and suppresssteinerpoint().                                  //
+// Each Steiner point is either removed or shifted into the interior.        //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::suppresssteinerpoints()
+{
+
+  if (!b->quiet) {
+    printf("Suppressing Steiner points ...\n");
+  }
+
+  point rempt, *parypt;
+
+  int bak_fliplinklevel = b->fliplinklevel;
+  b->fliplinklevel = 100000; // Unlimited flip level.
+  int suppcount = 0, remcount = 0;
+  int i;
+
+  // Try to suppress boundary Steiner points.
+  for (i = 0; i < subvertstack->objects; i++) {
+    parypt = (point *) fastlookup(subvertstack, i);
+    rempt = *parypt;
+    if (pointtype(rempt) != UNUSEDVERTEX) {
+      if ((pointtype(rempt) == FREESEGVERTEX) || 
+          (pointtype(rempt) == FREEFACETVERTEX)) {
+        if (suppressbdrysteinerpoint(rempt)) {
+          suppcount++;
+        }
+      }
+    }
+  } // i
+
+  if (suppcount > 0) {
+    if (b->verbose) {
+      printf("  Suppressed %d boundary Steiner points.\n", suppcount);
+    }
+  }
+
+  if (b->supsteiner_level > 0) { // -Y/1
+    for (i = 0; i < subvertstack->objects; i++) {
+      parypt = (point *) fastlookup(subvertstack, i);
+      rempt = *parypt;
+      if (pointtype(rempt) != UNUSEDVERTEX) {
+        if (pointtype(rempt) == FREEVOLVERTEX) {
+          if (removevertexbyflips(rempt)) {
+            remcount++;
+          }
+        }
+      }
+    }
+  }
+
+  if (remcount > 0) {
+    if (b->verbose) {
+      printf("  Removed %d interior Steiner points.\n", remcount);
+    }
+  }
+
+  b->fliplinklevel = bak_fliplinklevel;
+
+  if (b->supsteiner_level > 1) { // -Y/2
+    // Smooth interior Steiner points.
+    optparameters opm;
+    triface *parytet;
+    point *ppt;
+    REAL ori;
+    int smtcount, count, ivcount;
+    int nt, j;
+
+    // Point smooth options.
+    opm.max_min_volume = 1;
+    opm.numofsearchdirs = 20;
+    opm.searchstep = 0.001;
+    opm.maxiter = 30; // Limit the maximum iterations.
+
+    smtcount = 0;
+
+    do {
+
+      nt = 0;
+
+      while (1) {
+        count = 0;
+        ivcount = 0; // Clear the inverted count.
+
+        for (i = 0; i < subvertstack->objects; i++) {
+          parypt = (point *) fastlookup(subvertstack, i);
+          rempt = *parypt;
+          if (pointtype(rempt) == FREEVOLVERTEX) {
+            getvertexstar(1, rempt, cavetetlist, NULL, NULL);
+            // Calculate the initial smallest volume (maybe zero or negative).
+            for (j = 0; j < cavetetlist->objects; j++) {
+              parytet = (triface *) fastlookup(cavetetlist, j);
+              ppt = (point *) &(parytet->tet[4]);
+              ori = orient3dfast(ppt[1], ppt[0], ppt[2], ppt[3]);
+              if (j == 0) {
+                opm.initval = ori;
+              } else {
+                if (opm.initval > ori) opm.initval = ori; 
+              }
+            }
+            if (smoothpoint(rempt, cavetetlist, 1, &opm)) {
+              count++;
+            }
+            if (opm.imprval <= 0.0) {
+              ivcount++; // The mesh contains inverted elements.
+            }
+            cavetetlist->restart();
+          }
+        } // i
+
+        smtcount += count;
+
+        if (count == 0) {
+          // No point has been smoothed.
+          break;
+        }
+
+        nt++;
+        if (nt > 2) {
+          break; // Already three iterations.
+        }
+      } // while
+
+      if (ivcount > 0) {
+        // There are inverted elements!
+        if (opm.maxiter > 0) {
+          // Set unlimited smoothing steps. Try again.
+          opm.numofsearchdirs = 30;
+          opm.searchstep = 0.0001;
+          opm.maxiter = -1;
+          continue;
+        }
+      }
+
+      break;
+    } while (1); // Additional loop for (ivcount > 0)
+
+    if (ivcount > 0) {
+      printf("BUG Report!  The mesh contain inverted elements.\n");
+    }
+
+    if (b->verbose) {
+      if (smtcount > 0) {
+        printf("  Smoothed %d Steiner points.\n", smtcount); 
+      }
+    }
+  } // -Y2
+
+  subvertstack->restart();
+
+  return 1;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// recoverboundary()    Recover segments and facets.                         //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::recoverboundary(clock_t& tv)
+{
+  arraypool *misseglist, *misshlist;
+  arraypool *bdrysteinerptlist;
+  face searchsh, *parysh;
+  face searchseg, *paryseg;
+  point rempt, *parypt;
+  long ms; // The number of missing segments/subfaces.
+  int nit; // The number of iterations.
+  int s, i;
+
+  // Counters.
+  long bak_segref_count, bak_facref_count, bak_volref_count;
+
+  if (!b->quiet) {
+    printf("Recovering boundaries...\n");
+  }
+
+
+  if (b->verbose) {
+    printf("  Recovering segments.\n");
+  }
+
+  // Segments will be introduced.
+  checksubsegflag = 1;
+
+  misseglist = new arraypool(sizeof(face), 8);
+  bdrysteinerptlist = new arraypool(sizeof(point), 8);
+
+  // In random order.
+  subsegs->traversalinit();
+  for (i = 0; i < subsegs->items; i++) {
+    s = randomnation(i + 1);
+    // Move the s-th seg to the i-th.
+    subsegstack->newindex((void **) &paryseg);
+    *paryseg = * (face *) fastlookup(subsegstack, s);
+    // Put i-th seg to be the s-th.
+    searchseg.sh = shellfacetraverse(subsegs);
+    paryseg = (face *) fastlookup(subsegstack, s);
+    *paryseg = searchseg;
+  }
+
+  // The init number of missing segments.
+  ms = subsegs->items;
+  nit = 0; 
+  if (b->fliplinklevel < 0) {
+    autofliplinklevel = 1; // Init value.
+  }
+
+  // First, trying to recover segments by only doing flips.
+  while (1) {
+    recoversegments(misseglist, 0, 0);
+
+    if (misseglist->objects > 0) {
+      if (b->fliplinklevel >= 0) {
+        break;
+      } else {
+        if (misseglist->objects >= ms) {
+          nit++;
+          if (nit >= 3) {
+            //break;
+            // Do the last round with unbounded flip link level.
+            b->fliplinklevel = 100000;
+          }
+        } else {
+          ms = misseglist->objects;
+          if (nit > 0) {
+            nit--;
+          }
+        }
+        for (i = 0; i < misseglist->objects; i++) {
+          subsegstack->newindex((void **) &paryseg);
+          *paryseg = * (face *) fastlookup(misseglist, i);
+        }
+        misseglist->restart();
+        autofliplinklevel+=b->fliplinklevelinc;
+      }
+    } else {
+      // All segments are recovered.
+      break;
+    }
+  } // while (1)
+
+  if (b->verbose) {
+    printf("  %ld (%ld) segments are recovered (missing).\n", 
+           subsegs->items - misseglist->objects, misseglist->objects);
+  }
+
+  if (misseglist->objects > 0) {
+    // Second, trying to recover segments by doing more flips (fullsearch).
+    while (misseglist->objects > 0) {
+      ms = misseglist->objects;
+      for (i = 0; i < misseglist->objects; i++) {
+        subsegstack->newindex((void **) &paryseg);
+        *paryseg = * (face *) fastlookup(misseglist, i);
+      }
+      misseglist->restart();
+
+      recoversegments(misseglist, 1, 0);
+
+      if (misseglist->objects < ms) {
+        // The number of missing segments is reduced.
+        continue;
+      } else {
+        break;
+      }
+    }
+    if (b->verbose) {
+      printf("  %ld (%ld) segments are recovered (missing).\n", 
+             subsegs->items - misseglist->objects, misseglist->objects);
+    }
+  }
+
+  if (misseglist->objects > 0) {
+    // Third, trying to recover segments by doing more flips (fullsearch)
+    //   and adding Steiner points in the volume.
+    while (misseglist->objects > 0) {
+      ms = misseglist->objects;
+      for (i = 0; i < misseglist->objects; i++) {
+        subsegstack->newindex((void **) &paryseg);
+        *paryseg = * (face *) fastlookup(misseglist, i);
+      }
+      misseglist->restart();
+
+      recoversegments(misseglist, 1, 1);
+
+      if (misseglist->objects < ms) {
+        // The number of missing segments is reduced.
+        continue;
+      } else {
+        break;
+      }
+    }
+    if (b->verbose) {
+      printf("  Added %ld Steiner points in volume.\n", st_volref_count);
+    }
+  }
+
+  if (misseglist->objects > 0) {
+    // Last, trying to recover segments by doing more flips (fullsearch),
+    //   and adding Steiner points in the volume, and splitting segments.
+    long bak_inpoly_count = st_volref_count; //st_inpoly_count;
+    for (i = 0; i < misseglist->objects; i++) {
+      subsegstack->newindex((void **) &paryseg);
+      *paryseg = * (face *) fastlookup(misseglist, i);
+    }
+    misseglist->restart();
+
+    recoversegments(misseglist, 1, 2);
+
+    if (b->verbose) {
+      printf("  Added %ld Steiner points in segments.\n", st_segref_count);
+      if (st_volref_count > bak_inpoly_count) {
+        printf("  Added another %ld Steiner points in volume.\n", 
+               st_volref_count - bak_inpoly_count);
+      }
+    }
+  }
+
+
+  if (st_segref_count > 0) {
+    // Try to remove the Steiner points added in segments.
+    bak_segref_count = st_segref_count;
+    bak_volref_count = st_volref_count;
+    for (i = 0; i < subvertstack->objects; i++) {
+      // Get the Steiner point.
+      parypt = (point *) fastlookup(subvertstack, i);
+      rempt = *parypt;
+      if (!removevertexbyflips(rempt)) {
+        // Save it in list.
+        bdrysteinerptlist->newindex((void **) &parypt);
+        *parypt = rempt;
+      }
+    }
+    if (b->verbose) {
+      if (st_segref_count < bak_segref_count) {
+        if (bak_volref_count < st_volref_count) {
+          printf("  Suppressed %ld Steiner points in segments.\n", 
+                 st_volref_count - bak_volref_count);
+        }
+        if ((st_segref_count + (st_volref_count - bak_volref_count)) <
+            bak_segref_count) {
+          printf("  Removed %ld Steiner points in segments.\n", 
+                 bak_segref_count - 
+                   (st_segref_count + (st_volref_count - bak_volref_count)));
+        }
+      }
+    }
+    subvertstack->restart();
+  }
+
+
+  tv = clock();
+
+  if (b->verbose) {
+    printf("  Recovering facets.\n");
+  }
+
+  // Subfaces will be introduced.
+  checksubfaceflag = 1;
+
+  misshlist = new arraypool(sizeof(face), 8);
+
+  // Randomly order the subfaces.
+  subfaces->traversalinit();
+  for (i = 0; i < subfaces->items; i++) {
+    s = randomnation(i + 1);
+    // Move the s-th subface to the i-th.
+    subfacstack->newindex((void **) &parysh);
+    *parysh = * (face *) fastlookup(subfacstack, s);
+    // Put i-th subface to be the s-th.
+    searchsh.sh = shellfacetraverse(subfaces);
+    parysh = (face *) fastlookup(subfacstack, s);
+    *parysh = searchsh;
+  }
+
+  ms = subfaces->items;
+  nit = 0; 
+  b->fliplinklevel = -1; // Init.
+  if (b->fliplinklevel < 0) {
+    autofliplinklevel = 1; // Init value.
+  }
+
+  while (1) {
+    recoversubfaces(misshlist, 0);
+
+    if (misshlist->objects > 0) {
+      if (b->fliplinklevel >= 0) {
+        break;
+      } else {
+        if (misshlist->objects >= ms) {
+          nit++;
+          if (nit >= 3) {
+            //break;
+            // Do the last round with unbounded flip link level.
+            b->fliplinklevel = 100000;
+          }
+        } else {
+          ms = misshlist->objects;
+          if (nit > 0) {
+            nit--;
+          }
+        }
+        for (i = 0; i < misshlist->objects; i++) {
+          subfacstack->newindex((void **) &parysh);
+          *parysh = * (face *) fastlookup(misshlist, i);
+        }
+        misshlist->restart();
+        autofliplinklevel+=b->fliplinklevelinc;
+      }
+    } else {
+      // All subfaces are recovered.
+      break;
+    }
+  } // while (1)
+
+  if (b->verbose) {
+    printf("  %ld (%ld) subfaces are recovered (missing).\n", 
+           subfaces->items - misshlist->objects, misshlist->objects);
+  }
+
+  if (misshlist->objects > 0) {
+    // There are missing subfaces. Add Steiner points.
+    for (i = 0; i < misshlist->objects; i++) {
+      subfacstack->newindex((void **) &parysh);
+      *parysh = * (face *) fastlookup(misshlist, i);
+    }
+    misshlist->restart();
+
+    recoversubfaces(NULL, 1);
+
+    if (b->verbose) {
+      printf("  Added %ld Steiner points in facets.\n", st_facref_count);
+    }
+  }
+
+
+  if (st_facref_count > 0) {
+    // Try to remove the Steiner points added in facets.
+    bak_facref_count = st_facref_count;
+    for (i = 0; i < subvertstack->objects; i++) {
+      // Get the Steiner point.
+      parypt = (point *) fastlookup(subvertstack, i);
+      rempt = *parypt;
+      if (!removevertexbyflips(*parypt)) {
+        // Save it in list.
+        bdrysteinerptlist->newindex((void **) &parypt);
+        *parypt = rempt;
+      }
+    }
+    if (b->verbose) {
+      if (st_facref_count < bak_facref_count) {
+        printf("  Removed %ld Steiner points in facets.\n", 
+               bak_facref_count - st_facref_count);
+      }
+    }
+    subvertstack->restart();
+  }
+
+
+  if (bdrysteinerptlist->objects > 0) {
+    if (b->verbose) {
+      printf("  %ld Steiner points remained in boundary.\n",
+             bdrysteinerptlist->objects);
+    }
+  } // if
+
+
+  // Accumulate the dynamic memory.
+  totalworkmemory += (misseglist->totalmemory + misshlist->totalmemory +
+                      bdrysteinerptlist->totalmemory);
+
+  delete bdrysteinerptlist;
+  delete misseglist;
+  delete misshlist;
+}
+
+////                                                                       ////
+////                                                                       ////
+//// steiner_cxx //////////////////////////////////////////////////////////////
+
+
+//// reconstruct_cxx //////////////////////////////////////////////////////////
+////                                                                       ////
+////                                                                       ////
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// carveholes()    Remove tetrahedra not in the mesh domain.                 //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+
+void tetgenmesh::carveholes()
+{
+  arraypool *tetarray, *hullarray;
+  triface tetloop, neightet, *parytet, *parytet1;
+  triface *regiontets = NULL;
+  face checksh, *parysh;
+  face checkseg;
+  point ptloop, *parypt;
+  int t1ver;
+  int i, j, k;
+
+  if (!b->quiet) {
+    if (b->convex) {
+      printf("Marking exterior tetrahedra ...\n");
+    } else {
+      printf("Removing exterior tetrahedra ...\n");
+    }
+  }
+
+  // Initialize the pool of exterior tets.
+  tetarray = new arraypool(sizeof(triface), 10);
+  hullarray = new arraypool(sizeof(triface), 10);
+
+  // Collect unprotected tets and hull tets.
+  tetrahedrons->traversalinit();
+  tetloop.ver = 11; // The face opposite to dummypoint.
+  tetloop.tet = alltetrahedrontraverse();
+  while (tetloop.tet != (tetrahedron *) NULL) {
+    if (ishulltet(tetloop)) {
+      // Is this side protected by a subface?
+      if (!issubface(tetloop)) {
+        // Collect an unprotected hull tet and tet.
+        infect(tetloop);
+        hullarray->newindex((void **) &parytet);
+        *parytet = tetloop;
+        // tetloop's face number is 11 & 3 = 3.
+        decode(tetloop.tet[3], neightet);
+        if (!infected(neightet)) {
+          infect(neightet);
+          tetarray->newindex((void **) &parytet);
+          *parytet = neightet;
+        }
+      }
+    }
+    tetloop.tet = alltetrahedrontraverse();
+  }
+
+  if (in->numberofholes > 0) {
+    // Mark as infected any tets inside volume holes.
+    for (i = 0; i < 3 * in->numberofholes; i += 3) {
+      // Search a tet containing the i-th hole point.
+      neightet.tet = NULL;
+      randomsample(&(in->holelist[i]), &neightet);
+      if (locate(&(in->holelist[i]), &neightet) != OUTSIDE) {
+        // The tet 'neightet' contain this point.
+        if (!infected(neightet)) {
+          infect(neightet);
+          tetarray->newindex((void **) &parytet);
+          *parytet = neightet;
+          // Add its adjacent tet if it is not protected.
+          if (!issubface(neightet)) {
+            decode(neightet.tet[neightet.ver & 3], tetloop);
+            if (!infected(tetloop)) {
+              infect(tetloop);
+              if (ishulltet(tetloop)) {
+                hullarray->newindex((void **) &parytet);
+              } else {
+                tetarray->newindex((void **) &parytet);
+              }
+              *parytet = tetloop;
+            }
+          }
+          else {
+            // It is protected. Check if its adjacent tet is a hull tet.
+            decode(neightet.tet[neightet.ver & 3], tetloop);
+            if (ishulltet(tetloop)) {
+              // It is hull tet, add it into the list. Moreover, the subface
+              //   is dead, i.e., both sides are in exterior.
+              if (!infected(tetloop)) {
+                infect(tetloop);
+                hullarray->newindex((void **) &parytet);
+                *parytet = tetloop;
+              }
+            }
+            if (infected(tetloop)) {
+              // Both sides of this subface are in exterior.
+              tspivot(neightet, checksh);
+              sinfect(checksh); // Only queue it once.
+              subfacstack->newindex((void **) &parysh);
+              *parysh = checksh;
+            }
+          }
+        } // if (!infected(neightet))
+      } else {
+        // A hole point locates outside of the convex hull.
+        if (!b->quiet) {
+          printf("Warning:  The %d-th hole point ", i/3 + 1);
+          printf("lies outside the convex hull.\n");
+        }
+      }
+    } // i
+  } // if (in->numberofholes > 0)
+
+  if (b->regionattrib && (in->numberofregions > 0)) { // -A option.
+    // Record the tetrahedra that contains the region points for assigning
+    //   region attributes after the holes have been carved.
+    regiontets = new triface[in->numberofregions];
+    // Mark as marktested any tetrahedra inside volume regions.
+    for (i = 0; i < 5 * in->numberofregions; i += 5) {
+      // Search a tet containing the i-th region point.
+      neightet.tet = NULL;
+      randomsample(&(in->regionlist[i]), &neightet);
+      if (locate(&(in->regionlist[i]), &neightet) != OUTSIDE) {
+        regiontets[i/5] = neightet;
+      } else {
+        if (!b->quiet) {
+          printf("Warning:  The %d-th region point ", i/5+1);
+          printf("lies outside the convex hull.\n");
+        }
+        regiontets[i/5].tet = NULL;
+      }
+    }
+  }
+
+  // Collect all exterior tets (in concave place and in holes).
+  for (i = 0; i < tetarray->objects; i++) {
+    parytet = (triface *) fastlookup(tetarray, i);
+    j = (parytet->ver & 3); // j is the current face number.
+    // Check the other three adjacent tets.
+    for (k = 1; k < 4; k++) {
+      decode(parytet->tet[(j + k) % 4], neightet); 
+      // neightet may be a hull tet.
+      if (!infected(neightet)) {
+        // Is neightet protected by a subface.
+        if (!issubface(neightet)) {
+          // Not proected. Collect it. (It must not be a hull tet).
+          infect(neightet);
+          tetarray->newindex((void **) &parytet1);
+          *parytet1 = neightet;
+        } else {
+          // Protected. Check if it is a hull tet.
+          if (ishulltet(neightet)) {
+            // A hull tet. Collect it.
+            infect(neightet);
+            hullarray->newindex((void **) &parytet1);
+            *parytet1 = neightet;
+            // Both sides of this subface are exterior.
+            tspivot(neightet, checksh);
+            // Queue this subface (to be deleted later).
+            sinfect(checksh); // Only queue it once.
+            subfacstack->newindex((void **) &parysh);
+            *parysh = checksh;
+          }
+        }
+      } else {
+        // Both sides of this face are in exterior.
+        // If there is a subface. It should be collected.
+        if (issubface(neightet)) {
+          tspivot(neightet, checksh);
+          if (!sinfected(checksh)) {
+            sinfect(checksh);
+            subfacstack->newindex((void **) &parysh);
+            *parysh = checksh;
+          }
+        }
+      }
+    } // j, k
+  } // i
+
+  if (b->regionattrib && (in->numberofregions > 0)) {
+    // Re-check saved region tets to see if they lie outside.
+    for (i = 0; i < in->numberofregions; i++) {
+      if (infected(regiontets[i])) {
+        if (b->verbose) {
+          printf("Warning:  The %d-th region point ", i+1);
+          printf("lies in the exterior of the domain.\n");
+        }
+        regiontets[i].tet = NULL;
+      }
+    }
+  }
+
+  // Collect vertices which point to infected tets. These vertices
+  //   may get deleted after the removal of exterior tets.
+  //   If -Y1 option is used, collect all Steiner points for removal.
+  //   The lists 'cavetetvertlist' and 'subvertstack' are re-used.
+  points->traversalinit();
+  ptloop = pointtraverse();
+  while (ptloop != NULL) {
+    if ((pointtype(ptloop) != UNUSEDVERTEX) &&
+        (pointtype(ptloop) != DUPLICATEDVERTEX)) {
+      decode(point2tet(ptloop), neightet);
+      if (infected(neightet)) {
+        cavetetvertlist->newindex((void **) &parypt);
+        *parypt = ptloop;
+      }
+      if (b->nobisect && (b->supsteiner_level > 0)) { // -Y/1
+        // Queue it if it is a Steiner point.
+        if (pointmark(ptloop) > 
+              (in->numberofpoints - (in->firstnumber ? 0 : 1))) {
+          subvertstack->newindex((void **) &parypt);
+          *parypt = ptloop;
+        }
+      }
+    }
+    ptloop = pointtraverse();
+  }
+
+  if (!b->convex && (tetarray->objects > 0l)) { // No -c option.
+    // Remove exterior tets. Hull tets are updated.
+    arraypool *newhullfacearray;
+    triface hulltet, casface;
+    face segloop, *paryseg;
+    point pa, pb, pc;
+    long delsegcount = 0l;
+ 
+    // Collect segments which point to infected tets. Some segments
+    //   may get deleted after the removal of exterior tets.
+    subsegs->traversalinit();
+    segloop.sh = shellfacetraverse(subsegs);
+    while (segloop.sh != NULL) {
+      sstpivot1(segloop, neightet);
+      if (infected(neightet)) {
+        subsegstack->newindex((void **) &paryseg);
+        *paryseg = segloop;
+      }
+      segloop.sh = shellfacetraverse(subsegs);
+    }
+
+    newhullfacearray = new arraypool(sizeof(triface), 10);
+
+    // Create and save new hull tets.
+    for (i = 0; i < tetarray->objects; i++) {
+      parytet = (triface *) fastlookup(tetarray, i);
+      for (j = 0; j < 4; j++) {
+        decode(parytet->tet[j], tetloop);
+        if (!infected(tetloop)) {
+          // Found a new hull face (must be a subface).
+          tspivot(tetloop, checksh);
+          maketetrahedron(&hulltet);
+          pa = org(tetloop);
+          pb = dest(tetloop);
+          pc = apex(tetloop);
+          setvertices(hulltet, pb, pa, pc, dummypoint);
+          bond(tetloop, hulltet);
+          // Update the subface-to-tet map.
+          sesymself(checksh);
+          tsbond(hulltet, checksh);
+          // Update the segment-to-tet map.
+          for (k = 0; k < 3; k++) {
+            if (issubseg(tetloop)) {
+              tsspivot1(tetloop, checkseg);
+              tssbond1(hulltet, checkseg);
+              sstbond1(checkseg, hulltet);
+            }
+            enextself(tetloop);
+            eprevself(hulltet);
+          }
+          // Update the point-to-tet map.
+          setpoint2tet(pa, (tetrahedron) tetloop.tet);
+          setpoint2tet(pb, (tetrahedron) tetloop.tet);
+          setpoint2tet(pc, (tetrahedron) tetloop.tet);
+          // Save the exterior tet at this hull face. It still holds pointer
+          //   to the adjacent interior tet. Use it to connect new hull tets. 
+          newhullfacearray->newindex((void **) &parytet1);
+          parytet1->tet = parytet->tet;
+          parytet1->ver = j;
+        } // if (!infected(tetloop))
+      } // j
+    } // i
+
+    // Connect new hull tets.
+    for (i = 0; i < newhullfacearray->objects; i++) {
+      parytet = (triface *) fastlookup(newhullfacearray, i);
+      fsym(*parytet, neightet);
+      // Get the new hull tet.
+      fsym(neightet, hulltet);
+      for (j = 0; j < 3; j++) {
+        esym(hulltet, casface);
+        if (casface.tet[casface.ver & 3] == NULL) {
+          // Since the boundary of the domain may not be a manifold, we
+          //   find the adjacent hull face by traversing the tets in the
+          //   exterior (which are all infected tets).
+          neightet = *parytet;
+          while (1) {
+            fnextself(neightet);
+            if (!infected(neightet)) break;
+          }
+          if (!ishulltet(neightet)) {
+            // An interior tet. Get the new hull tet.
+            fsymself(neightet);
+            esymself(neightet);
+          } 
+          // Bond them together.
+          bond(casface, neightet);
+        }
+        enextself(hulltet);
+        enextself(*parytet);
+      } // j
+    } // i
+
+    if (subfacstack->objects > 0l) {
+      // Remove all subfaces which do not attach to any tetrahedron.
+      //   Segments which are not attached to any subfaces and tets
+      //   are deleted too.
+      face casingout, casingin;
+
+      for (i = 0; i < subfacstack->objects; i++) {
+        parysh = (face *) fastlookup(subfacstack, i);
+        if (i == 0) {
+          if (b->verbose) {
+            printf("Warning:  Removed an exterior face (%d, %d, %d) #%d\n",
+                   pointmark(sorg(*parysh)), pointmark(sdest(*parysh)),
+                   pointmark(sapex(*parysh)), shellmark(*parysh));
+          }
+        }
+        // Dissolve this subface from face links.
+        for (j = 0; j < 3; j++) {         
+          spivot(*parysh, casingout);
+          sspivot(*parysh, checkseg);
+          if (casingout.sh != NULL) {
+            casingin = casingout;
+            while (1) {
+              spivot(casingin, checksh);
+              if (checksh.sh == parysh->sh) break;
+              casingin = checksh;
+            }
+            if (casingin.sh != casingout.sh) {
+              // Update the link: ... -> casingin -> casingout ->...
+              sbond1(casingin, casingout);
+            } else {
+              // Only one subface at this edge is left.
+              sdissolve(casingout);
+            }
+            if (checkseg.sh != NULL) {
+              // Make sure the segment does not connect to a dead one.
+              ssbond(casingout, checkseg);
+            }
+          } else {
+            if (checkseg.sh != NULL) {
+              //if (checkseg.sh[3] != NULL) {
+              if (delsegcount == 0) {
+                if (b->verbose) {
+                  printf("Warning:  Removed an exterior segment (%d, %d) #%d\n",
+                         pointmark(sorg(checkseg)), pointmark(sdest(checkseg)),
+                         shellmark(checkseg));
+                }
+              }
+              shellfacedealloc(subsegs, checkseg.sh);
+              delsegcount++;
+            }
+          }
+          senextself(*parysh);
+        } // j
+        // Delete this subface.
+        shellfacedealloc(subfaces, parysh->sh);
+      } // i
+      if (b->verbose) {
+        printf("  Deleted %ld subfaces.\n", subfacstack->objects);
+      }
+      subfacstack->restart();
+    } // if (subfacstack->objects > 0l)
+
+    if (subsegstack->objects > 0l) {
+      for (i = 0; i < subsegstack->objects; i++) {
+        paryseg = (face *) fastlookup(subsegstack, i);
+        if (paryseg->sh && (paryseg->sh[3] != NULL)) {
+          sstpivot1(*paryseg, neightet);
+          if (infected(neightet)) {
+            if (b->verbose) {
+              printf("Warning:  Removed an exterior segment (%d, %d) #%d\n",
+                     pointmark(sorg(*paryseg)), pointmark(sdest(*paryseg)),
+                     shellmark(*paryseg));
+            }
+            shellfacedealloc(subsegs, paryseg->sh);
+            delsegcount++;
+          }
+        }
+      }
+      subsegstack->restart();
+    } // if (subsegstack->objects > 0l)
+
+    if (delsegcount > 0) {
+      if (b->verbose) {
+        printf("  Deleted %ld segments.\n", delsegcount);
+      }
+    }
+
+    if (cavetetvertlist->objects > 0l) {
+      // Some vertices may lie in exterior. Marke them as UNUSEDVERTEX.
+      long delvertcount = unuverts;
+      long delsteinercount = 0l;
+
+      for (i = 0; i < cavetetvertlist->objects; i++) {
+        parypt = (point *) fastlookup(cavetetvertlist, i);
+        decode(point2tet(*parypt), neightet);
+        if (infected(neightet)) {
+          // Found an exterior vertex.
+          if (pointmark(*parypt) > 
+                (in->numberofpoints - (in->firstnumber ? 0 : 1))) {
+            // A Steiner point.
+            if (pointtype(*parypt) == FREESEGVERTEX) {
+              st_segref_count--;
+            } else if (pointtype(*parypt) == FREEFACETVERTEX) {
+              st_facref_count--;
+            } else {
+              st_volref_count--;
+            }
+            delsteinercount++;
+            if (steinerleft > 0) steinerleft++;
+          }
+          setpointtype(*parypt, UNUSEDVERTEX);
+          unuverts++;
+        }
+      }
+
+      if (b->verbose) {
+        if (unuverts > delvertcount) {
+          if (delsteinercount > 0l) {
+            if (unuverts > (delvertcount + delsteinercount)) {
+              printf("  Removed %ld exterior input vertices.\n", 
+                     unuverts - delvertcount - delsteinercount);
+            }
+            printf("  Removed %ld exterior Steiner vertices.\n", 
+                   delsteinercount);
+          } else {
+            printf("  Removed %ld exterior input vertices.\n", 
+                   unuverts - delvertcount);
+          }
+        }
+      }
+      cavetetvertlist->restart();
+      // Comment: 'subvertstack' will be cleaned in routine
+      //   suppresssteinerpoints().
+    } // if (cavetetvertlist->objects > 0l)
+
+    // Update the hull size.
+    hullsize += (newhullfacearray->objects - hullarray->objects);
+
+    // Delete all exterior tets and old hull tets.
+    for (i = 0; i < tetarray->objects; i++) {
+      parytet = (triface *) fastlookup(tetarray, i);
+      tetrahedrondealloc(parytet->tet);
+    }
+    tetarray->restart();
+
+    for (i = 0; i < hullarray->objects; i++) {
+      parytet = (triface *) fastlookup(hullarray, i);
+      tetrahedrondealloc(parytet->tet);
+    }
+    hullarray->restart();
+
+    delete newhullfacearray;
+  } // if (!b->convex && (tetarray->objects > 0l))
+
+  if (b->convex && (tetarray->objects > 0l)) { // With -c option
+    // In this case, all exterior tets get a region marker '-1'.
+    int attrnum = numelemattrib - 1;
+
+    for (i = 0; i < tetarray->objects; i++) {
+      parytet = (triface *) fastlookup(tetarray, i);
+      setelemattribute(parytet->tet, attrnum, -1);
+    }
+    tetarray->restart();
+
+    for (i = 0; i < hullarray->objects; i++) {
+      parytet = (triface *) fastlookup(hullarray, i);
+      uninfect(*parytet);
+    }
+    hullarray->restart();
+
+    if (subfacstack->objects > 0l) {
+      for (i = 0; i < subfacstack->objects; i++) {
+        parysh = (face *) fastlookup(subfacstack, i);
+        suninfect(*parysh);
+      }
+      subfacstack->restart();
+    }
+
+    if (cavetetvertlist->objects > 0l) {
+      cavetetvertlist->restart();
+    }
+  } // if (b->convex && (tetarray->objects > 0l))
+
+  if (b->regionattrib) { // With -A option.
+    if (!b->quiet) {
+      printf("Spreading region attributes.\n");
+    }
+    REAL volume;
+    int attr, maxattr = 0; // Choose a small number here.
+    int attrnum = numelemattrib - 1; 
+    // Comment: The element region marker is at the end of the list of
+    //   the element attributes.
+    int regioncount = 0;
+
+    // If has user-defined region attributes.
+    if (in->numberofregions > 0) {
+      // Spread region attributes.
+      for (i = 0; i < 5 * in->numberofregions; i += 5) {
+        if (regiontets[i/5].tet != NULL) {
+          attr = (int) in->regionlist[i + 3];
+          if (attr > maxattr) {
+            maxattr = attr;
+          }
+          volume = in->regionlist[i + 4];
+          tetarray->restart(); // Re-use this array.
+          infect(regiontets[i/5]);
+          tetarray->newindex((void **) &parytet);
+          *parytet = regiontets[i/5];
+          // Collect and set attrs for all tets of this region.
+          for (j = 0; j < tetarray->objects; j++) {
+            parytet = (triface *) fastlookup(tetarray, j);
+            tetloop = *parytet;
+            setelemattribute(tetloop.tet, attrnum, attr);
+            if (b->varvolume) { // If has -a option.
+              setvolumebound(tetloop.tet, volume);
+            }
+            for (k = 0; k < 4; k++) {
+              decode(tetloop.tet[k], neightet);
+              // Is the adjacent already checked?
+              if (!infected(neightet)) {
+                // Is this side protected by a subface?
+                if (!issubface(neightet)) {
+                  infect(neightet);
+                  tetarray->newindex((void **) &parytet);
+                  *parytet = neightet;
+                }
+              }
+            } // k
+          } // j
+          regioncount++;
+        } // if (regiontets[i/5].tet != NULL)
+      } // i
+    }
+
+    // Set attributes for all tetrahedra.
+    attr = maxattr + 1;
+    tetrahedrons->traversalinit();
+    tetloop.tet = tetrahedrontraverse();
+    while (tetloop.tet != (tetrahedron *) NULL) {
+      if (!infected(tetloop)) {
+        // An unmarked region.
+        tetarray->restart(); // Re-use this array.
+        infect(tetloop);
+        tetarray->newindex((void **) &parytet);
+        *parytet = tetloop;
+        // Find and mark all tets.
+        for (j = 0; j < tetarray->objects; j++) {
+          parytet = (triface *) fastlookup(tetarray, j);
+          tetloop = *parytet;
+          setelemattribute(tetloop.tet, attrnum, attr);
+          for (k = 0; k < 4; k++) {
+            decode(tetloop.tet[k], neightet);
+            // Is the adjacent tet already checked?
+            if (!infected(neightet)) {
+              // Is this side protected by a subface?
+              if (!issubface(neightet)) {
+                infect(neightet);
+                tetarray->newindex((void **) &parytet);
+                *parytet = neightet;
+              }
+            }
+          } // k
+        } // j
+        attr++; // Increase the attribute.
+        regioncount++;
+      }
+      tetloop.tet = tetrahedrontraverse();
+    }
+    // Until here, every tet has a region attribute.
+
+    // Uninfect processed tets.
+    tetrahedrons->traversalinit();
+    tetloop.tet = tetrahedrontraverse();
+    while (tetloop.tet != (tetrahedron *) NULL) {
+      uninfect(tetloop);
+      tetloop.tet = tetrahedrontraverse();
+    }
+
+    if (b->verbose) {
+      //assert(regioncount > 0);
+      if (regioncount > 1) {
+        printf("  Found %d subdomains.\n", regioncount);
+      } else {
+        printf("  Found %d domain.\n", regioncount);
+      }
+    }
+  } // if (b->regionattrib)
+
+  if (regiontets != NULL) {
+    delete [] regiontets;
+  }
+  delete tetarray;
+  delete hullarray;
+
+  if (!b->convex) { // No -c option
+    // The mesh is non-convex now.
+    nonconvex = 1;
+
+    // Push all hull tets into 'flipstack'.
+    tetrahedrons->traversalinit();
+    tetloop.ver = 11; // The face opposite to dummypoint.
+    tetloop.tet = alltetrahedrontraverse();
+    while (tetloop.tet != (tetrahedron *) NULL) {
+      if ((point) tetloop.tet[7] == dummypoint) {
+        fsym(tetloop, neightet);
+        flippush(flipstack, &neightet);
+      }
+      tetloop.tet = alltetrahedrontraverse();
+    }
+
+    flipconstraints fc;
+    fc.enqflag = 2;
+    long sliver_peel_count = lawsonflip3d(&fc);
+
+    if (sliver_peel_count > 0l) {
+      if (b->verbose) {
+        printf("  Removed %ld hull slivers.\n", sliver_peel_count);
+      }
+    }
+    unflipqueue->restart();
+  } // if (!b->convex)
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// enqueuesubface()    Queue a subface or a subsegment for encroachment chk. //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::enqueuesubface(memorypool *pool, face *chkface)
+{
+  if (!smarktest2ed(*chkface)) {
+    smarktest2(*chkface); // Only queue it once.
+    face *queface = (face *) pool->alloc();
+    *queface = *chkface;
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// enqueuetetrahedron()    Queue a tetrahedron for quality check.            //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::enqueuetetrahedron(triface *chktet)
+{
+  if (!marktest2ed(*chktet)) {
+    marktest2(*chktet); // Only queue it once.
+    triface *quetet = (triface *) badtetrahedrons->alloc();
+    *quetet = *chktet;
+  }
+}
+
+//// optimize_cxx /////////////////////////////////////////////////////////////
+////                                                                       ////
+////                                                                       ////
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// lawsonflip3d()    A three-dimensional Lawson's algorithm.                 //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+long tetgenmesh::lawsonflip3d(flipconstraints *fc)
+{
+  triface fliptets[5], neightet, hulltet;
+  face checksh, casingout;
+  badface *popface, *bface;
+  point pd, pe, *pts;
+  REAL sign, ori;
+  REAL vol, len3;
+  long flipcount, totalcount = 0l;
+  long sliver_peels = 0l;
+  int t1ver;
+  int i;
+
+
+  while (1) {
+
+    if (b->verbose > 2) {
+      printf("      Lawson flip %ld faces.\n", flippool->items);
+    }
+    flipcount = 0l;
+
+    while (flipstack != (badface *) NULL) {
+      // Pop a face from the stack.
+      popface = flipstack;
+      fliptets[0] = popface->tt;
+      flipstack = flipstack->nextitem; // The next top item in stack.
+      flippool->dealloc((void *) popface);
+
+      // Skip it if it is a dead tet (destroyed by previous flips).
+      if (isdeadtet(fliptets[0])) continue;
+      // Skip it if it is not the same tet as we saved.
+      if (!facemarked(fliptets[0])) continue;
+
+      unmarkface(fliptets[0]);
+
+      if (ishulltet(fliptets[0])) continue;
+
+      fsym(fliptets[0], fliptets[1]);
+      if (ishulltet(fliptets[1])) {
+        if (nonconvex) {
+          // Check if 'fliptets[0]' it is a hull sliver.
+          tspivot(fliptets[0], checksh);
+          for (i = 0; i < 3; i++) {
+            if (!isshsubseg(checksh)) {
+              spivot(checksh, casingout);
+              //assert(casingout.sh != NULL);
+              if (sorg(checksh) != sdest(casingout)) sesymself(casingout);
+              stpivot(casingout, neightet);
+              if (neightet.tet == fliptets[0].tet) {
+                // Found a hull sliver 'neightet'. Let it be [e,d,a,b], where 
+                //   [e,d,a] and [d,e,b] are hull faces.
+                edestoppo(neightet, hulltet); // [a,b,e,d]
+                fsymself(hulltet); // [b,a,e,#]
+                if (oppo(hulltet) == dummypoint) {
+                  pe = org(neightet);
+                  if ((pointtype(pe) == FREEFACETVERTEX) ||
+                      (pointtype(pe) == FREESEGVERTEX)) {
+                    removevertexbyflips(pe);
+                  }
+                } else {
+                  eorgoppo(neightet, hulltet); // [b,a,d,e]
+                  fsymself(hulltet); // [a,b,d,#]
+                  if (oppo(hulltet) == dummypoint) {
+                    pd = dest(neightet);
+                    if ((pointtype(pd) == FREEFACETVERTEX) ||
+                        (pointtype(pd) == FREESEGVERTEX)) {
+                      removevertexbyflips(pd);
+                    }
+                  } else {
+                    // Perform a 3-to-2 flip to remove the sliver.
+                    fliptets[0] = neightet;          // [e,d,a,b]
+                    fnext(fliptets[0], fliptets[1]); // [e,d,b,c]
+                    fnext(fliptets[1], fliptets[2]); // [e,d,c,a]
+                    flip32(fliptets, 1, fc);
+                    // Update counters.
+                    flip32count--;
+                    flip22count--;
+                    sliver_peels++;
+                    if (fc->remove_ndelaunay_edge) {
+                      // Update the volume (must be decreased).
+                      //assert(fc->tetprism_vol_sum <= 0);
+                      tetprism_vol_sum += fc->tetprism_vol_sum;
+                      fc->tetprism_vol_sum = 0.0; // Clear it.
+                    }
+                  }
+                }
+                break;
+              } // if (neightet.tet == fliptets[0].tet)
+            } // if (!isshsubseg(checksh))
+            senextself(checksh);
+          } // i
+        } // if (nonconvex)
+        continue;
+      }
+
+      if (checksubfaceflag) {
+        // Do not flip if it is a subface.
+        if (issubface(fliptets[0])) continue;
+      }
+
+      // Test whether the face is locally Delaunay or not.
+      pts = (point *) fliptets[1].tet; 
+      sign = insphere_s(pts[4], pts[5], pts[6], pts[7], oppo(fliptets[0]));
+
+      if (sign < 0) {
+        // A non-Delaunay face. Try to flip it.
+        pd = oppo(fliptets[0]);
+        pe = oppo(fliptets[1]);
+
+        // Use the length of the edge [d,e] as a reference to determine
+        //   a nearly degenerated new tet.
+        len3 = distance(pd, pe);
+        len3 = (len3 * len3 * len3);
+
+        // Check the convexity of its three edges. Stop checking either a
+        //   locally non-convex edge (ori < 0) or a flat edge (ori = 0) is
+        //   encountered, and 'fliptet' represents that edge.
+        for (i = 0; i < 3; i++) {
+          ori = orient3d(org(fliptets[0]), dest(fliptets[0]), pd, pe);
+          if (ori > 0) {
+            // Avoid creating a nearly degenerated new tet at boundary.
+            //   Re-use fliptets[2], fliptets[3];
+            esym(fliptets[0], fliptets[2]);
+            esym(fliptets[1], fliptets[3]);
+            if (issubface(fliptets[2]) || issubface(fliptets[3])) {
+              vol = orient3dfast(org(fliptets[0]), dest(fliptets[0]), pd, pe);
+              if ((fabs(vol) / len3) < b->epsilon) {
+                ori = 0.0; // Do rounding.
+              }
+            }
+          } // Rounding check
+          if (ori <= 0) break;
+          enextself(fliptets[0]);
+          eprevself(fliptets[1]);
+        }
+
+        if (ori > 0) {
+          // A 2-to-3 flip is found.
+          //   [0] [a,b,c,d], 
+          //   [1] [b,a,c,e]. no dummypoint.
+          flip23(fliptets, 0, fc);
+          flipcount++;
+          if (fc->remove_ndelaunay_edge) {
+            // Update the volume (must be decreased).
+            //assert(fc->tetprism_vol_sum <= 0);
+            tetprism_vol_sum += fc->tetprism_vol_sum;
+            fc->tetprism_vol_sum = 0.0; // Clear it.
+          }
+          continue;
+        } else { // ori <= 0
+          // The edge ('fliptets[0]' = [a',b',c',d]) is non-convex or flat,
+          //   where the edge [a',b'] is one of [a,b], [b,c], and [c,a].
+          if (checksubsegflag) {
+            // Do not flip if it is a segment.
+            if (issubseg(fliptets[0])) continue;
+          }
+          // Check if there are three or four tets sharing at this edge.        
+          esymself(fliptets[0]); // [b,a,d,c]
+          for (i = 0; i < 3; i++) {
+            fnext(fliptets[i], fliptets[i+1]);
+          }
+          if (fliptets[3].tet == fliptets[0].tet) {
+            // A 3-to-2 flip is found. (No hull tet.)
+            flip32(fliptets, 0, fc); 
+            flipcount++;
+            if (fc->remove_ndelaunay_edge) {
+              // Update the volume (must be decreased).
+              //assert(fc->tetprism_vol_sum <= 0);
+              tetprism_vol_sum += fc->tetprism_vol_sum;
+              fc->tetprism_vol_sum = 0.0; // Clear it.
+            }
+            continue;
+          } else {
+            // There are more than 3 tets at this edge.
+            fnext(fliptets[3], fliptets[4]);
+            if (fliptets[4].tet == fliptets[0].tet) {
+              // There are exactly 4 tets at this edge.
+              if (nonconvex) {
+                if (apex(fliptets[3]) == dummypoint) {
+                  // This edge is locally non-convex on the hull.
+                  // It can be removed by a 4-to-4 flip.                  
+                  ori = 0;
+                }
+              } // if (nonconvex)
+              if (ori == 0) {
+                // A 4-to-4 flip is found. (Two hull tets may be involved.)
+                // Current tets in 'fliptets':
+                //   [0] [b,a,d,c] (d may be newpt)
+                //   [1] [b,a,c,e]
+                //   [2] [b,a,e,f] (f may be dummypoint)
+                //   [3] [b,a,f,d]
+                esymself(fliptets[0]); // [a,b,c,d] 
+                // A 2-to-3 flip replaces face [a,b,c] by edge [e,d].
+                //   This creates a degenerate tet [e,d,a,b] (tmpfliptets[0]).
+                //   It will be removed by the followed 3-to-2 flip.
+                flip23(fliptets, 0, fc); // No hull tet.
+                fnext(fliptets[3], fliptets[1]);
+                fnext(fliptets[1], fliptets[2]);
+                // Current tets in 'fliptets':
+                //   [0] [...]
+                //   [1] [b,a,d,e] (degenerated, d may be new point).
+                //   [2] [b,a,e,f] (f may be dummypoint)
+                //   [3] [b,a,f,d]
+                // A 3-to-2 flip replaces edge [b,a] by face [d,e,f].
+                //   Hull tets may be involved (f may be dummypoint).
+                flip32(&(fliptets[1]), (apex(fliptets[3]) == dummypoint), fc);
+                flipcount++;
+                flip23count--;
+                flip32count--;
+                flip44count++;
+                if (fc->remove_ndelaunay_edge) {
+                  // Update the volume (must be decreased).
+                  //assert(fc->tetprism_vol_sum <= 0);
+                  tetprism_vol_sum += fc->tetprism_vol_sum;
+                  fc->tetprism_vol_sum = 0.0; // Clear it.
+                }
+                continue;
+              } // if (ori == 0)
+            }
+          }
+        } // if (ori <= 0)
+
+        // This non-Delaunay face is unflippable. Save it.
+        unflipqueue->newindex((void **) &bface);
+        bface->tt = fliptets[0];
+        bface->forg  = org(fliptets[0]);
+        bface->fdest = dest(fliptets[0]);
+        bface->fapex = apex(fliptets[0]);
+      } // if (sign < 0)
+    } // while (flipstack)
+
+    if (b->verbose > 2) {
+      if (flipcount > 0) {
+        printf("      Performed %ld flips.\n", flipcount);
+      }
+    }
+    // Accumulate the counter of flips.
+    totalcount += flipcount;
+
+    // Return if no unflippable faces left.
+    if (unflipqueue->objects == 0l) break; 
+    // Return if no flip has been performed.
+    if (flipcount == 0l) break;
+
+    // Try to flip the unflippable faces.
+    for (i = 0; i < unflipqueue->objects; i++) {
+      bface = (badface *) fastlookup(unflipqueue, i);
+      if (!isdeadtet(bface->tt) && 
+          (org(bface->tt) == bface->forg) &&
+          (dest(bface->tt) == bface->fdest) &&
+          (apex(bface->tt) == bface->fapex)) {
+        flippush(flipstack, &(bface->tt));
+      }
+    }
+    unflipqueue->restart();
+
+  } // while (1)
+
+  if (b->verbose > 2) {
+    if (totalcount > 0) {
+      printf("      Performed %ld flips.\n", totalcount);
+    }
+    if (sliver_peels > 0) {
+      printf("      Removed %ld hull slivers.\n", sliver_peels);
+    }
+    if (unflipqueue->objects > 0l) {
+      printf("      %ld unflippable edges remained.\n", unflipqueue->objects);
+    }
+  }
+
+  return totalcount + sliver_peels;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// recoverdelaunay()    Recovery the locally Delaunay property.              //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::recoverdelaunay()
+{
+  arraypool *flipqueue, *nextflipqueue, *swapqueue;
+  triface tetloop, neightet, *parytet;
+  badface *bface, *parybface;
+  point *ppt;
+  flipconstraints fc;
+  int i, j;
+
+  if (!b->quiet) {
+    printf("Recovering Delaunayness...\n");
+  }
+
+  tetprism_vol_sum = 0.0; // Initialize it.
+
+  // Put all interior faces of the mesh into 'flipstack'.
+  tetrahedrons->traversalinit();
+  tetloop.tet = tetrahedrontraverse();
+  while (tetloop.tet != NULL) {
+    for (tetloop.ver = 0; tetloop.ver < 4; tetloop.ver++) {
+      decode(tetloop.tet[tetloop.ver], neightet);
+      if (!facemarked(neightet)) {
+        flippush(flipstack, &tetloop);
+      }
+    }
+    ppt = (point *) &(tetloop.tet[4]);
+    tetprism_vol_sum += tetprismvol(ppt[0], ppt[1], ppt[2], ppt[3]);
+    tetloop.tet = tetrahedrontraverse();
+  }
+
+  // Calulate a relatively lower bound for small improvement. 
+  //   Used to avoid rounding error in volume calculation.
+  fc.bak_tetprism_vol = tetprism_vol_sum * b->epsilon * 1e-3;
+
+  if (b->verbose) {
+    printf("  Initial obj = %.17g\n", tetprism_vol_sum);
+  }
+
+  if (b->verbose > 1) {
+    printf("    Recover Delaunay [Lawson] : %ld\n", flippool->items);
+  }
+
+  // First only use the basic Lawson's flip.
+  fc.remove_ndelaunay_edge = 1;
+  fc.enqflag = 2;
+
+  lawsonflip3d(&fc);
+
+  if (b->verbose > 1) {
+    printf("    obj (after Lawson) = %.17g\n", tetprism_vol_sum);
+  }
+
+  if (unflipqueue->objects == 0l) {
+    return; // The mesh is Delaunay.
+  }
+
+  fc.unflip = 1; // Unflip if the edge is not flipped.
+  fc.collectnewtets = 1; // new tets are returned in 'cavetetlist'.
+  fc.enqflag = 0;
+
+  autofliplinklevel = 1; // Init level.
+  b->fliplinklevel = -1; // No fixed level.
+
+  // For efficiency reason, we limit the maximium size of the edge star.
+  int bakmaxflipstarsize = b->flipstarsize;
+  b->flipstarsize = 10; // default
+
+  flipqueue = new arraypool(sizeof(badface), 10);
+  nextflipqueue = new arraypool(sizeof(badface), 10);
+  
+  // Swap the two flip queues.
+  swapqueue = flipqueue;
+  flipqueue = unflipqueue;
+  unflipqueue = swapqueue;
+
+  while (flipqueue->objects > 0l) {
+
+    if (b->verbose > 1) {
+      printf("    Recover Delaunay [level = %2d] #:  %ld.\n",
+             autofliplinklevel, flipqueue->objects);
+    }
+
+    for (i = 0; i < flipqueue->objects; i++) {
+      bface  = (badface *) fastlookup(flipqueue, i);
+      if (getedge(bface->forg, bface->fdest, &bface->tt)) {
+        if (removeedgebyflips(&(bface->tt), &fc) == 2) {
+          tetprism_vol_sum += fc.tetprism_vol_sum;
+          fc.tetprism_vol_sum = 0.0; // Clear it.
+          // Queue new faces for flips.
+          for (j = 0; j < cavetetlist->objects; j++) {
+            parytet = (triface *) fastlookup(cavetetlist, j);
+            // A queued new tet may be dead.
+            if (!isdeadtet(*parytet)) {
+              for (parytet->ver = 0; parytet->ver < 4; parytet->ver++) {
+                // Avoid queue a face twice.
+                decode(parytet->tet[parytet->ver], neightet);
+                if (!facemarked(neightet)) {
+                  flippush(flipstack, parytet);
+                }
+              } // parytet->ver
+            }
+          } // j
+          cavetetlist->restart();
+          // Remove locally non-Delaunay faces. New non-Delaunay edges
+          //   may be found. They are saved in 'unflipqueue'.
+          fc.enqflag = 2;
+          lawsonflip3d(&fc);
+          fc.enqflag = 0;
+          // There may be unflipable faces. Add them in flipqueue.
+          for (j = 0; j < unflipqueue->objects; j++) {
+            bface  = (badface *) fastlookup(unflipqueue, j);
+            flipqueue->newindex((void **) &parybface);
+            *parybface = *bface;
+          }
+          unflipqueue->restart();
+        } else {
+          // Unable to remove this edge. Save it.
+          nextflipqueue->newindex((void **) &parybface);
+          *parybface = *bface;
+          // Normally, it should be zero. 
+          //assert(fc.tetprism_vol_sum == 0.0);
+          // However, due to rounding errors, a tiny value may appear.
+          fc.tetprism_vol_sum = 0.0;
+        }
+      }
+    } // i
+
+    if (b->verbose > 1) {
+      printf("    obj (after level %d) = %.17g.\n", autofliplinklevel,
+             tetprism_vol_sum);
+    }
+    flipqueue->restart();
+
+    // Swap the two flip queues.
+    swapqueue = flipqueue;
+    flipqueue = nextflipqueue;
+    nextflipqueue = swapqueue;
+
+    if (flipqueue->objects > 0l) {
+      // default 'b->delmaxfliplevel' is 1.
+      if (autofliplinklevel >= b->delmaxfliplevel) {
+        // For efficiency reason, we do not search too far.
+        break;
+      }
+      autofliplinklevel+=b->fliplinklevelinc;
+    }
+  } // while (flipqueue->objects > 0l)
+
+  if (flipqueue->objects > 0l) {
+    if (b->verbose > 1) {
+      printf("    %ld non-Delaunay edges remained.\n", flipqueue->objects);
+    }
+  }
+
+  if (b->verbose) {
+    printf("  Final obj  = %.17g\n", tetprism_vol_sum);
+  }
+
+  b->flipstarsize = bakmaxflipstarsize;
+  delete flipqueue;
+  delete nextflipqueue;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// gettetrahedron()    Get a tetrahedron which have the given vertices.      //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::gettetrahedron(point pa, point pb, point pc, point pd, 
+                               triface *searchtet)
+{
+  triface spintet;
+  int t1ver; 
+
+  if (getedge(pa, pb, searchtet)) {
+    spintet = *searchtet;
+    while (1) {
+      if (apex(spintet) == pc) {
+        *searchtet = spintet;
+        break;
+      }
+      fnextself(spintet);
+      if (spintet.tet == searchtet->tet) break;
+    }
+    if (apex(*searchtet) == pc) {
+      if (oppo(*searchtet) == pd) {
+        return 1;
+      } else {
+        fsymself(*searchtet);
+        if (oppo(*searchtet) == pd) {
+          return 1;
+        }
+      }
+    }
+  }
+
+  return 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// improvequalitybyflips()    Improve the mesh quality by flips.             //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+long tetgenmesh::improvequalitybyflips()
+{
+  arraypool *flipqueue, *nextflipqueue, *swapqueue;
+  badface *bface, *parybface;
+  triface *parytet;
+  point *ppt;
+  flipconstraints fc;
+  REAL *cosdd, ncosdd[6], maxdd;
+  long totalremcount, remcount;
+  int remflag;
+  int n, i, j, k;
+
+  //assert(unflipqueue->objects > 0l);
+  flipqueue = new arraypool(sizeof(badface), 10);
+  nextflipqueue = new arraypool(sizeof(badface), 10);
+
+  // Backup flip edge options.
+  int bakautofliplinklevel = autofliplinklevel;
+  int bakfliplinklevel = b->fliplinklevel;
+  int bakmaxflipstarsize = b->flipstarsize;
+
+  // Set flip edge options.
+  autofliplinklevel = 1; 
+  b->fliplinklevel = -1;
+  b->flipstarsize = 10; // b->optmaxflipstarsize;
+
+  fc.remove_large_angle = 1;
+  fc.unflip = 1;
+  fc.collectnewtets = 1;
+  fc.checkflipeligibility = 1;
+
+  totalremcount = 0l;
+
+  // Swap the two flip queues.
+  swapqueue = flipqueue;
+  flipqueue = unflipqueue;
+  unflipqueue = swapqueue;
+
+  while (flipqueue->objects > 0l) {
+
+    remcount = 0l;
+
+    while (flipqueue->objects > 0l) {
+      if (b->verbose > 1) {
+        printf("    Improving mesh qualiy by flips [%d]#:  %ld.\n",
+               autofliplinklevel, flipqueue->objects);
+      }
+
+      for (k = 0; k < flipqueue->objects; k++) {
+        bface  = (badface *) fastlookup(flipqueue, k);
+        if (gettetrahedron(bface->forg, bface->fdest, bface->fapex,
+                           bface->foppo, &bface->tt)) {
+          //assert(!ishulltet(bface->tt));
+          // There are bad dihedral angles in this tet.
+          if (bface->tt.ver != 11) {
+            // The dihedral angles are permuted.
+            // Here we simply re-compute them. Slow!!.
+            ppt = (point *) & (bface->tt.tet[4]);
+            tetalldihedral(ppt[0], ppt[1], ppt[2], ppt[3], bface->cent, 
+                           &bface->key, NULL);
+            bface->forg = ppt[0];
+            bface->fdest = ppt[1];
+            bface->fapex = ppt[2];
+            bface->foppo = ppt[3];
+            bface->tt.ver = 11;
+          }
+          if (bface->key == 0) {
+            // Re-comput the quality values. Due to smoothing operations.
+            ppt = (point *) & (bface->tt.tet[4]);
+            tetalldihedral(ppt[0], ppt[1], ppt[2], ppt[3], bface->cent, 
+                           &bface->key, NULL);
+          }
+          cosdd = bface->cent;
+          remflag = 0;
+          for (i = 0; (i < 6) && !remflag; i++) {
+            if (cosdd[i] < cosmaxdihed) {
+              // Found a large dihedral angle.
+              bface->tt.ver = edge2ver[i]; // Go to the edge.
+              fc.cosdihed_in = cosdd[i];
+              fc.cosdihed_out = 0.0; // 90 degree.
+              n = removeedgebyflips(&(bface->tt), &fc);
+              if (n == 2) {
+                // Edge is flipped.
+                remflag = 1;
+                if (fc.cosdihed_out < cosmaxdihed) {
+                  // Queue new bad tets for further improvements.
+                  for (j = 0; j < cavetetlist->objects; j++) {
+                    parytet = (triface *) fastlookup(cavetetlist, j);
+                    if (!isdeadtet(*parytet)) {
+                      ppt = (point *) & (parytet->tet[4]);
+                      // Do not test a hull tet.
+                      if (ppt[3] != dummypoint) {
+                        tetalldihedral(ppt[0], ppt[1], ppt[2], ppt[3], ncosdd, 
+                                       &maxdd, NULL);
+                        if (maxdd < cosmaxdihed) {
+                          // There are bad dihedral angles in this tet.
+                          nextflipqueue->newindex((void **) &parybface); 
+                          parybface->tt.tet = parytet->tet;
+                          parybface->tt.ver = 11;
+                          parybface->forg = ppt[0];
+                          parybface->fdest = ppt[1];
+                          parybface->fapex = ppt[2];
+                          parybface->foppo = ppt[3];
+                          parybface->key = maxdd;
+                          for (n = 0; n < 6; n++) {
+                            parybface->cent[n] = ncosdd[n];
+                          }
+                        }
+                      } // if (ppt[3] != dummypoint) 
+                    }
+                  } // j
+                } // if (fc.cosdihed_out < cosmaxdihed)
+                cavetetlist->restart();
+                remcount++;
+              }
+            }
+          } // i          
+          if (!remflag) {
+            // An unremoved bad tet. Queue it again. 
+            unflipqueue->newindex((void **) &parybface);
+            *parybface = *bface;
+          }
+        } // if (gettetrahedron(...))
+      } // k
+
+      flipqueue->restart();
+
+      // Swap the two flip queues.
+      swapqueue = flipqueue;
+      flipqueue = nextflipqueue;
+      nextflipqueue = swapqueue;
+    } // while (flipqueues->objects > 0)
+
+    if (b->verbose > 1) {
+      printf("    Removed %ld bad tets.\n", remcount);
+    }
+    totalremcount += remcount;
+
+    if (unflipqueue->objects > 0l) {
+      //if (autofliplinklevel >= b->optmaxfliplevel) {
+      if (autofliplinklevel >= b->optlevel) {
+        break;
+      }
+      autofliplinklevel+=b->fliplinklevelinc;
+      //b->flipstarsize = 10 + (1 << (b->optlevel - 1));
+    }
+
+    // Swap the two flip queues.
+    swapqueue = flipqueue;
+    flipqueue = unflipqueue;
+    unflipqueue = swapqueue;
+  } // while (flipqueues->objects > 0)
+
+  // Restore original flip edge options.
+  autofliplinklevel = bakautofliplinklevel;
+  b->fliplinklevel = bakfliplinklevel;
+  b->flipstarsize = bakmaxflipstarsize;
+
+  delete flipqueue;
+  delete nextflipqueue;
+
+  return totalremcount;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// smoothpoint()    Moving a vertex to improve the mesh quality.             //
+//                                                                           //
+// 'smtpt' (p) is a point to be smoothed. Generally, it is a Steiner point.  //
+// It may be not a vertex of the mesh.                                       //
+//                                                                           //
+// This routine tries to move 'p' inside its star until a selected objective //
+// function over all tetrahedra in the star is improved. The function may be //
+// the some quality measures, i.e., aspect ratio, maximum dihedral angel, or //
+// simply the volume of the tetrahedra.                                      //
+//                                                                           //
+// 'linkfacelist' contains the list of link faces of 'p'.  Since a link face //
+// has two orientations, ccw or cw, with respect to 'p'.  'ccw' indicates    //
+// the orientation is ccw (1) or not (0).                                    //
+//                                                                           //
+// 'opm' is a structure contains the parameters of the objective function.   //
+// It is needed by the evaluation of the function value.                     //
+//                                                                           //
+// The return value indicates weather the point is smoothed or not.          //
+//                                                                           //
+// ASSUMPTION: This routine assumes that all link faces are true faces, i.e, //
+// no face has 'dummypoint' as its vertex.                                   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::smoothpoint(point smtpt, arraypool *linkfacelist, int ccw,
+                            optparameters *opm)
+{
+  triface *parytet, *parytet1, swaptet;
+  point pa, pb, pc;
+  REAL fcent[3], startpt[3], nextpt[3], bestpt[3];
+  REAL oldval, minval = 0.0, val;
+  REAL maxcosd; // oldang, newang;
+  REAL ori, diff;
+  int numdirs, iter;
+  int i, j, k;
+
+  // Decide the number of moving directions.
+  numdirs = (int) linkfacelist->objects;
+  if (numdirs > opm->numofsearchdirs) {
+    numdirs = opm->numofsearchdirs; // Maximum search directions.
+  }
+
+  // Set the initial value.
+  opm->imprval = opm->initval;
+  iter = 0;
+
+  for (i = 0; i < 3; i++) {
+    bestpt[i] = startpt[i] = smtpt[i];
+  }
+
+  // Iterate until the obj function is not improved.
+  while (1) {
+
+    // Find the best next location.
+    oldval = opm->imprval;
+
+    for (i = 0; i < numdirs; i++) {
+      // Randomly pick a link face (0 <= k <= objects - i - 1).
+      k = (int) randomnation(linkfacelist->objects - i);
+      parytet = (triface *) fastlookup(linkfacelist, k);
+      // Calculate a new position from 'p' to the center of this face.
+      pa = org(*parytet);
+      pb = dest(*parytet);
+      pc = apex(*parytet);
+      for (j = 0; j < 3; j++) {
+        fcent[j] = (pa[j] + pb[j] + pc[j]) / 3.0;
+      }
+      for (j = 0; j < 3; j++) {
+        nextpt[j] = startpt[j] + opm->searchstep * (fcent[j] - startpt[j]); 
+      }
+      // Calculate the largest minimum function value for the new location.
+      for (j = 0; j < linkfacelist->objects; j++) {
+        parytet = (triface *) fastlookup(linkfacelist, j);
+        if (ccw) {
+          pa = org(*parytet);
+          pb = dest(*parytet);
+        } else {
+          pb = org(*parytet);
+          pa = dest(*parytet);
+        }
+        pc = apex(*parytet);
+        ori = orient3d(pa, pb, pc, nextpt);
+        if (ori < 0.0) {
+          // Calcuate the objective function value. 
+          if (opm->max_min_volume) {
+            //val = -ori;
+            val = - orient3dfast(pa, pb, pc, nextpt);
+          } else if (opm->min_max_aspectratio) {
+            val = 1.0 / tetaspectratio(pa, pb, pc, nextpt);
+          } else if (opm->min_max_dihedangle) {
+            tetalldihedral(pa, pb, pc, nextpt, NULL, &maxcosd, NULL);
+            if (maxcosd < -1) maxcosd = -1.0; // Rounding.
+            val = maxcosd + 1.0; // Make it be positive. 
+          } else {
+            // Unknown objective function.
+            val = 0.0;
+          }  
+        } else { // ori >= 0.0;
+          // An invalid new tet. 
+          // This may happen if the mesh contains inverted elements.
+          if (opm->max_min_volume) {
+            //val = -ori;
+            val = - orient3dfast(pa, pb, pc, nextpt);    
+          } else {
+            // Discard this point.
+            break; // j
+          }
+        } // if (ori >= 0.0)
+        // Stop looping when the object value is not improved.
+        if (val <= opm->imprval) {
+          break; // j
+        } else {
+          // Remember the smallest improved value.
+          if (j == 0) {
+            minval = val;
+          } else {
+            minval = (val < minval) ? val : minval;
+          }
+        }
+      } // j
+      if (j == linkfacelist->objects) {
+        // The function value has been improved.
+        opm->imprval = minval;
+        // Save the new location of the point.
+        for (j = 0; j < 3; j++) bestpt[j] = nextpt[j];
+      }
+      // Swap k-th and (object-i-1)-th entries.
+      j = linkfacelist->objects - i - 1;
+      parytet  = (triface *) fastlookup(linkfacelist, k);
+      parytet1 = (triface *) fastlookup(linkfacelist, j);
+      swaptet = *parytet1;
+      *parytet1 = *parytet;
+      *parytet = swaptet;
+    } // i
+
+    diff = opm->imprval - oldval;
+    if (diff > 0.0) {
+      // Is the function value improved effectively?
+      if (opm->max_min_volume) {
+        //if ((diff / oldval) < b->epsilon) diff = 0.0;  
+      } else if (opm->min_max_aspectratio) {
+        if ((diff / oldval) < 1e-3) diff = 0.0;
+      } else if (opm->min_max_dihedangle) {
+        //oldang = acos(oldval - 1.0);
+        //newang = acos(opm->imprval - 1.0);
+        //if ((oldang - newang) < 0.00174) diff = 0.0; // about 0.1 degree.
+      } else {
+        // Unknown objective function.
+        terminatetetgen(this, 2); 
+      }
+    }
+
+    if (diff > 0.0) {
+      // Yes, move p to the new location and continue.
+      for (j = 0; j < 3; j++) startpt[j] = bestpt[j];
+      iter++;
+      if ((opm->maxiter > 0) && (iter >= opm->maxiter)) {
+        // Maximum smoothing iterations reached.
+        break;
+      }
+    } else {
+      break;
+    }
+
+  } // while (1)
+
+  if (iter > 0) {
+    // The point has been smoothed.
+    opm->smthiter = iter; // Remember the number of iterations. 
+    // The point has been smoothed. Update it to its new position.
+    for (i = 0; i < 3; i++) smtpt[i] = startpt[i];
+  }
+
+  return iter;
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// improvequalitysmoothing()    Improve mesh quality by smoothing.           //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+long tetgenmesh::improvequalitybysmoothing(optparameters *opm)
+{
+  arraypool *flipqueue, *swapqueue;
+  triface *parytet;
+  badface *bface, *parybface;
+  point *ppt;
+  long totalsmtcount, smtcount;
+  int smtflag;
+  int iter, i, j, k;
+
+  //assert(unflipqueue->objects > 0l);
+  flipqueue = new arraypool(sizeof(badface), 10);
+
+  // Swap the two flip queues.
+  swapqueue = flipqueue;
+  flipqueue = unflipqueue;
+  unflipqueue = swapqueue;
+
+  totalsmtcount = 0l;
+  iter = 0;
+
+  while (flipqueue->objects > 0l) {
+
+    smtcount = 0l;
+
+    if (b->verbose > 1) {
+      printf("    Improving mesh quality by smoothing [%d]#:  %ld.\n",
+             iter, flipqueue->objects);
+    }
+
+    for (k = 0; k < flipqueue->objects; k++) {      
+      bface  = (badface *) fastlookup(flipqueue, k);
+      if (gettetrahedron(bface->forg, bface->fdest, bface->fapex,
+                         bface->foppo, &bface->tt)) {
+        // Operate on it if it is not in 'unflipqueue'.
+        if (!marktested(bface->tt)) {
+          // Here we simply re-compute the quality. Since other smoothing
+          //   operation may have moved the vertices of this tet.
+          ppt = (point *) & (bface->tt.tet[4]);
+          tetalldihedral(ppt[0], ppt[1], ppt[2], ppt[3], bface->cent, 
+                         &bface->key, NULL);
+          if (bface->key < cossmtdihed) { // if (maxdd < cosslidihed) {
+            // It is a sliver. Try to smooth its vertices.
+            smtflag = 0;
+            opm->initval = bface->key + 1.0; 
+            for (i = 0; (i < 4) && !smtflag; i++) {
+              if (pointtype(ppt[i]) == FREEVOLVERTEX) {
+                getvertexstar(1, ppt[i], cavetetlist, NULL, NULL);
+                opm->searchstep = 0.001; // Search step size
+                smtflag = smoothpoint(ppt[i], cavetetlist, 1, opm);
+                if (smtflag) {
+                  while (opm->smthiter == opm->maxiter) {
+                    opm->searchstep *= 10.0; // Increase the step size.
+                    opm->initval = opm->imprval;
+                    opm->smthiter = 0; // reset
+                    smoothpoint(ppt[i], cavetetlist, 1, opm);
+                  }
+                  // This tet is modifed.
+                  smtcount++;
+                  if ((opm->imprval - 1.0) < cossmtdihed) {
+                    // There are slivers in new tets. Queue them.
+                    for (j = 0; j < cavetetlist->objects; j++) {
+                      parytet = (triface *) fastlookup(cavetetlist, j);
+                      // Operate it if it is not in 'unflipqueue'.
+                      if (!marktested(*parytet)) {
+                        // Evaluate its quality.
+                        // Re-use ppt, bface->key, bface->cent.
+                        ppt = (point *) & (parytet->tet[4]);
+                        tetalldihedral(ppt[0], ppt[1], ppt[2], ppt[3], 
+                                       bface->cent, &bface->key, NULL);
+                        if (bface->key < cossmtdihed) {
+                          // A new sliver. Queue it.
+                          marktest(*parytet); // It is in unflipqueue.
+                          unflipqueue->newindex((void **) &parybface);
+                          parybface->tt = *parytet;
+                          parybface->forg = ppt[0];
+                          parybface->fdest = ppt[1];
+                          parybface->fapex = ppt[2];
+                          parybface->foppo = ppt[3];
+                          parybface->tt.ver = 11; 
+                          parybface->key = 0.0;
+                        }
+                      }
+                    } // j
+                  } // if ((opm->imprval - 1.0) < cossmtdihed)
+                } // if (smtflag)
+                cavetetlist->restart();
+              } // if (pointtype(ppt[i]) == FREEVOLVERTEX)
+            } // i
+            if (!smtflag) {
+              // Didn't smooth. Queue it again.
+              marktest(bface->tt); // It is in unflipqueue.
+              unflipqueue->newindex((void **) &parybface);
+              parybface->tt = bface->tt;
+              parybface->forg = ppt[0];
+              parybface->fdest = ppt[1];
+              parybface->fapex = ppt[2];
+              parybface->foppo = ppt[3];
+              parybface->tt.ver = 11;
+              parybface->key = 0.0;
+            }
+	      } // if (maxdd < cosslidihed)
+        } // if (!marktested(...))
+      } // if (gettetrahedron(...))
+    } // k
+
+    flipqueue->restart();
+
+    // Unmark the tets in unflipqueue.
+    for (i = 0; i < unflipqueue->objects; i++) {
+      bface  = (badface *) fastlookup(unflipqueue, i);
+      unmarktest(bface->tt);
+    }
+
+    if (b->verbose > 1) {
+      printf("    Smooth %ld points.\n", smtcount);
+    }
+    totalsmtcount += smtcount;
+
+    if (smtcount == 0l) {
+      // No point has been smoothed. 
+      break;
+    } else {
+      iter++;
+      if (iter == 2) { //if (iter >= b->optpasses) {
+        break;
+      }
+    }
+
+    // Swap the two flip queues.
+    swapqueue = flipqueue;
+    flipqueue = unflipqueue;
+    unflipqueue = swapqueue;
+  } // while
+
+  delete flipqueue;
+
+  return totalsmtcount;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// splitsliver()    Split a sliver.                                          //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+int tetgenmesh::splitsliver(triface *slitet, REAL cosd, int chkencflag)
+{
+  triface *abtets;
+  triface searchtet, spintet, *parytet;
+  point pa, pb, steinerpt;
+  optparameters opm;
+  insertvertexflags ivf;
+  REAL smtpt[3], midpt[3];
+  int success;
+  int t1ver;
+  int n, i;
+
+  // 'slitet' is [c,d,a,b], where [c,d] has a big dihedral angle. 
+  // Go to the opposite edge [a,b].
+  edestoppo(*slitet, searchtet); // [a,b,c,d].
+
+  // Do not split a segment.
+  if (issubseg(searchtet)) {
+    return 0; 
+  }
+
+  // Count the number of tets shared at [a,b].
+  // Do not split it if it is a hull edge.
+  spintet = searchtet;
+  n = 0; 
+  while (1) {
+    if (ishulltet(spintet)) break;
+    n++;
+    fnextself(spintet);
+    if (spintet.tet == searchtet.tet) break;
+  }
+  if (ishulltet(spintet)) {
+    return 0; // It is a hull edge.
+  }
+
+  // Get all tets at edge [a,b].
+  abtets = new triface[n];
+  spintet = searchtet;
+  for (i = 0; i < n; i++) {
+    abtets[i] = spintet;
+    fnextself(spintet);
+  }
+
+  // Initialize the list of 2n boundary faces.
+  for (i = 0; i < n; i++) {    
+    eprev(abtets[i], searchtet);
+    esymself(searchtet); // [a,p_i,p_i+1].
+    cavetetlist->newindex((void **) &parytet);
+    *parytet = searchtet;
+    enext(abtets[i], searchtet);
+    esymself(searchtet); // [p_i,b,p_i+1].
+    cavetetlist->newindex((void **) &parytet);
+    *parytet = searchtet;
+  }
+
+  // Init the Steiner point at the midpoint of edge [a,b].
+  pa = org(abtets[0]);
+  pb = dest(abtets[0]);
+  for (i = 0; i < 3; i++) {
+    smtpt[i] = midpt[i] = 0.5 * (pa[i] + pb[i]);
+  }
+
+  // Point smooth options.
+  opm.min_max_dihedangle = 1;
+  opm.initval = cosd + 1.0; // Initial volume is zero.
+  opm.numofsearchdirs = 20;
+  opm.searchstep = 0.001;  
+  opm.maxiter = 100; // Limit the maximum iterations.
+
+  success = smoothpoint(smtpt, cavetetlist, 1, &opm);
+
+  if (success) {
+    while (opm.smthiter == opm.maxiter) {
+      // It was relocated and the prescribed maximum iteration reached. 
+      // Try to increase the search stepsize.
+      opm.searchstep *= 10.0;
+      //opm.maxiter = 100; // Limit the maximum iterations.
+      opm.initval = opm.imprval;
+      opm.smthiter = 0; // Init.
+      smoothpoint(smtpt, cavetetlist, 1, &opm);  
+    }
+  } // if (success)
+
+  cavetetlist->restart();
+
+  if (!success) {
+    delete [] abtets;
+    return 0;
+  }
+
+
+  // Insert the Steiner point.
+  makepoint(&steinerpt, FREEVOLVERTEX);
+  for (i = 0; i < 3; i++) steinerpt[i] = smtpt[i];
+
+  // Insert the created Steiner point.
+  for (i = 0; i < n; i++) {
+    infect(abtets[i]);
+    caveoldtetlist->newindex((void **) &parytet);
+    *parytet = abtets[i];
+  }
+
+  searchtet = abtets[0]; // No need point location.
+  if (b->metric) {
+    locate(steinerpt, &searchtet); // For size interpolation.
+  }
+
+  delete [] abtets;
+
+  ivf.iloc = (int) INSTAR;
+  ivf.chkencflag = chkencflag;
+  ivf.assignmeshsize = b->metric; 
+
+
+  if (insertpoint(steinerpt, &searchtet, NULL, NULL, &ivf)) {
+    // The vertex has been inserted.
+    st_volref_count++; 
+    if (steinerleft > 0) steinerleft--;
+    return 1;
+  } else {
+    // The Steiner point is too close to an existing vertex. Reject it.
+    pointdealloc(steinerpt);
+    return 0;
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// removeslivers()    Remove slivers by adding Steiner points.               //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+long tetgenmesh::removeslivers(int chkencflag)
+{
+  arraypool *flipqueue, *swapqueue;
+  badface *bface, *parybface;
+  triface slitet, *parytet;
+  point *ppt;
+  REAL cosdd[6], maxcosd;
+  long totalsptcount, sptcount;
+  int iter, i, j, k;
+
+  //assert(unflipqueue->objects > 0l);
+  flipqueue = new arraypool(sizeof(badface), 10);
+
+  // Swap the two flip queues.
+  swapqueue = flipqueue;
+  flipqueue = unflipqueue;
+  unflipqueue = swapqueue;
+
+  totalsptcount = 0l;
+  iter = 0;
+
+  while ((flipqueue->objects > 0l) && (steinerleft != 0)) {
+
+    sptcount = 0l;
+
+    if (b->verbose > 1) {
+      printf("    Splitting bad quality tets [%d]#:  %ld.\n",
+             iter, flipqueue->objects);
+    }
+
+    for (k = 0; (k < flipqueue->objects) && (steinerleft != 0); k++) {      
+      bface  = (badface *) fastlookup(flipqueue, k);
+      if (gettetrahedron(bface->forg, bface->fdest, bface->fapex,
+                         bface->foppo, &bface->tt)) {
+        if ((bface->key == 0) || (bface->tt.ver != 11)) {
+          // Here we need to re-compute the quality. Since other smoothing
+          //   operation may have moved the vertices of this tet.
+          ppt = (point *) & (bface->tt.tet[4]);
+          tetalldihedral(ppt[0], ppt[1], ppt[2], ppt[3], bface->cent, 
+                         &bface->key, NULL);
+        }
+        if (bface->key < cosslidihed) { 
+          // It is a sliver. Try to split it.
+          slitet.tet = bface->tt.tet;
+          //cosdd = bface->cent;
+          for (j = 0; j < 6; j++) {
+            if (bface->cent[j] < cosslidihed) { 
+              // Found a large dihedral angle.
+              slitet.ver = edge2ver[j]; // Go to the edge.
+              if (splitsliver(&slitet, bface->cent[j], chkencflag)) {
+                sptcount++;
+                break;
+              }
+            }
+          } // j
+          if (j < 6) {
+            // A sliver is split. Queue new slivers.
+            badtetrahedrons->traversalinit();
+            parytet = (triface *) badtetrahedrons->traverse();
+            while (parytet != NULL) {
+              unmarktest2(*parytet);
+              ppt = (point *) & (parytet->tet[4]);
+              tetalldihedral(ppt[0], ppt[1], ppt[2], ppt[3], cosdd, 
+                             &maxcosd, NULL);
+              if (maxcosd < cosslidihed) {
+                // A new sliver. Queue it.
+                unflipqueue->newindex((void **) &parybface);
+                parybface->forg = ppt[0];
+                parybface->fdest = ppt[1];
+                parybface->fapex = ppt[2];
+                parybface->foppo = ppt[3];
+                parybface->tt.tet = parytet->tet;
+                parybface->tt.ver = 11;
+                parybface->key = maxcosd;
+                for (i = 0; i < 6; i++) {
+                  parybface->cent[i] = cosdd[i];
+                }
+              }
+              parytet = (triface *) badtetrahedrons->traverse();
+            }
+            badtetrahedrons->restart();
+          } else {
+            // Didn't split. Queue it again.
+            unflipqueue->newindex((void **) &parybface);
+            *parybface = *bface;
+          } // if (j == 6)
+        } // if (bface->key < cosslidihed)
+      } // if (gettetrahedron(...))
+    } // k
+
+    flipqueue->restart();
+
+    if (b->verbose > 1) {
+      printf("    Split %ld tets.\n", sptcount);
+    }
+    totalsptcount += sptcount;
+
+    if (sptcount == 0l) {
+      // No point has been smoothed. 
+      break;
+    } else {
+      iter++;
+      if (iter == 2) { //if (iter >= b->optpasses) {
+        break;
+      }
+    }
+
+    // Swap the two flip queues.
+    swapqueue = flipqueue;
+    flipqueue = unflipqueue;
+    unflipqueue = swapqueue;
+  } // while
+
+  delete flipqueue;
+
+  return totalsptcount;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// optimizemesh()    Optimize mesh for specified objective functions.        //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::optimizemesh()
+{
+  badface *parybface;
+  triface checktet;
+  point *ppt;
+  int optpasses;
+  optparameters opm;
+  REAL ncosdd[6], maxdd;
+  long totalremcount, remcount;
+  long totalsmtcount, smtcount;
+  long totalsptcount, sptcount;
+  int chkencflag;
+  int iter;
+  int n;
+
+  if (!b->quiet) {
+    printf("Optimizing mesh...\n");
+  }
+
+  optpasses = ((1 << b->optlevel) - 1);
+
+  if (b->verbose) {
+    printf("  Optimization level  = %d.\n", b->optlevel);
+    printf("  Optimization scheme = %d.\n", b->optscheme);
+    printf("  Number of iteration = %d.\n", optpasses);
+    printf("  Min_Max dihed angle = %g.\n", b->optmaxdihedral);
+  }
+
+  totalsmtcount = totalsptcount = totalremcount = 0l;
+
+  cosmaxdihed = cos(b->optmaxdihedral / 180.0 * PI);
+  cossmtdihed = cos(b->optminsmtdihed / 180.0 * PI);
+  cosslidihed = cos(b->optminslidihed / 180.0 * PI);
+
+  int attrnum = numelemattrib - 1; 
+
+  // Put all bad tetrahedra into array.
+  tetrahedrons->traversalinit();
+  checktet.tet = tetrahedrontraverse();
+  while (checktet.tet != NULL) {
+    if (b->convex) { // -c
+      // Skip this tet if it lies in the exterior.
+      if (elemattribute(checktet.tet, attrnum) == -1.0) {
+        checktet.tet = tetrahedrontraverse();
+        continue;
+      }
+    }
+    ppt = (point *) & (checktet.tet[4]);
+    tetalldihedral(ppt[0], ppt[1], ppt[2], ppt[3], ncosdd, &maxdd, NULL);
+    if (maxdd < cosmaxdihed) {
+      // There are bad dihedral angles in this tet.
+      unflipqueue->newindex((void **) &parybface); 
+      parybface->tt.tet = checktet.tet;
+      parybface->tt.ver = 11;
+      parybface->forg = ppt[0];
+      parybface->fdest = ppt[1];
+      parybface->fapex = ppt[2];
+      parybface->foppo = ppt[3];
+      parybface->key = maxdd;
+      for (n = 0; n < 6; n++) {
+        parybface->cent[n] = ncosdd[n];
+      }
+    }
+    checktet.tet = tetrahedrontraverse();
+  }
+
+  totalremcount = improvequalitybyflips();
+
+  if ((unflipqueue->objects > 0l) && 
+      ((b->optscheme & 2) || (b->optscheme & 4))) {
+    // The pool is only used by removeslivers().
+    badtetrahedrons = new memorypool(sizeof(triface), b->tetrahedraperblock,
+                                     sizeof(void *), 0);
+
+    // Smoothing options.
+    opm.min_max_dihedangle = 1;
+    opm.numofsearchdirs = 10;
+    // opm.searchstep = 0.001;  
+    opm.maxiter = 30; // Limit the maximum iterations.
+    //opm.checkencflag = 4; // Queue affected tets after smoothing.
+    chkencflag = 4; // Queue affected tets after splitting a sliver.
+    iter = 0;
+
+    while (iter < optpasses) {
+      smtcount = sptcount = remcount = 0l;
+      if (b->optscheme & 2) {
+        smtcount += improvequalitybysmoothing(&opm);
+        totalsmtcount += smtcount;
+        if (smtcount > 0l) {
+          remcount = improvequalitybyflips();
+          totalremcount += remcount;
+        }
+      }
+      if (unflipqueue->objects > 0l) {
+        if (b->optscheme & 4) {
+          sptcount += removeslivers(chkencflag);
+          totalsptcount += sptcount;
+          if (sptcount > 0l) {
+            remcount = improvequalitybyflips();
+            totalremcount += remcount;
+          }
+        }
+      }
+      if (unflipqueue->objects > 0l) {
+        if (remcount > 0l) {
+          iter++;
+        } else {
+          break;
+        }
+      } else {
+        break;
+      }
+    } // while (iter)
+
+    delete badtetrahedrons;
+    badtetrahedrons = NULL;
+  }
+
+  if (unflipqueue->objects > 0l) {
+    if (b->verbose > 1) {
+      printf("    %ld bad tets remained.\n", unflipqueue->objects);
+    }
+    unflipqueue->restart();
+  }
+
+  if (b->verbose) {
+    if (totalremcount > 0l) {
+      printf("  Removed %ld edges.\n", totalremcount);
+    }
+    if (totalsmtcount > 0l) {
+      printf("  Smoothed %ld points.\n", totalsmtcount);
+    }
+    if (totalsptcount > 0l) {
+      printf("  Split %ld slivers.\n", totalsptcount);
+    }
+  }
+}
+
+////                                                                       ////
+////                                                                       ////
+//// optimize_cxx /////////////////////////////////////////////////////////////
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// jettisonnodes()    Jettison unused or duplicated vertices.                //
+//                                                                           //
+// Unused points are those input points which are outside the mesh domain or //
+// have no connection (isolated) to the mesh.  Duplicated points exist for   //
+// example if the input PLC is read from a .stl mesh file (marked during the //
+// Delaunay tetrahedralization step. This routine remove these points from   //
+// points list. All existing points are reindexed.                           //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+void tetgenmesh::jettisonnodes()
+{
+  point pointloop;
+  bool jetflag;
+  int oldidx, newidx;
+  int remcount;
+
+  if (!b->quiet) {
+    printf("Jettisoning redundant points.\n");
+  }
+
+  points->traversalinit();
+  pointloop = pointtraverse();
+  oldidx = newidx = 0; // in->firstnumber;
+  remcount = 0;
+  while (pointloop != (point) NULL) {
+    jetflag = (pointtype(pointloop) == DUPLICATEDVERTEX) || 
+      (pointtype(pointloop) == UNUSEDVERTEX);
+    if (jetflag) {
+      // It is a duplicated or unused point, delete it.
+      pointdealloc(pointloop);
+      remcount++;
+    } else {
+      // Re-index it.
+      setpointmark(pointloop, newidx + in->firstnumber);
+      if (in->pointmarkerlist != (int *) NULL) {
+        if (oldidx < in->numberofpoints) {
+          // Re-index the point marker as well.
+          in->pointmarkerlist[newidx] = in->pointmarkerlist[oldidx];
+        }
+      }
+      newidx++;
+    }
+    oldidx++;
+    pointloop = pointtraverse();
+  }
+  if (b->verbose) {
+    printf("  %ld duplicated vertices are removed.\n", dupverts);
+    printf("  %ld unused vertices are removed.\n", unuverts);
+  }
+  dupverts = 0l;
+  unuverts = 0l;
+
+  // The following line ensures that dead items in the pool of nodes cannot
+  //   be allocated for the new created nodes. This ensures that the input
+  //   nodes will occur earlier in the output files, and have lower indices.
+  points->deaditemstack = (void *) NULL;
+}
+
+
diff --git a/Mesh/tetgenBR.h b/Mesh/tetgenBR.h
new file mode 100644
index 0000000000000000000000000000000000000000..849b185805c7aa3ba3b9d4dffd60eb669b89221e
--- /dev/null
+++ b/Mesh/tetgenBR.h
@@ -0,0 +1,2535 @@
+#ifndef tetgenBRH
+#define tetgenBRH
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// tetgenbehavior                                                            //
+//                                                                           //
+// A structure for maintaining the switches and parameters used by TetGen's  //
+// mesh data structure and algorithms.                                       //
+//                                                                           //
+// All switches and parameters are initialized with default values. They can //
+// be set by the command line arguments (a list of strings) of TetGen.       //
+//                                                                           //
+// NOTE: Some of the switches are incompatible. While some may depend on     //
+// other switches.  The routine parse_commandline() sets the switches from   //
+// the command line (a list of strings) and checks the consistency of the    //
+// applied switches.                                                         //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+class tetgenbehavior {
+
+public:
+
+  // Switches of TetGen. 
+  int plc;                                                         // '-p', 0.
+  int psc;                                                         // '-s', 0.
+  int refine;                                                      // '-r', 0.
+  int quality;                                                     // '-q', 0.
+  int nobisect;                                                    // '-Y', 0.
+  int coarsen;                                                     // '-R', 0.
+  int weighted;                                                    // '-w', 0.
+  int brio_hilbert;                                                // '-b', 1.
+  int incrflip;                                                    // '-l', 0.
+  int flipinsert;                                                  // '-L', 0.
+  int metric;                                                      // '-m', 0.
+  int varvolume;                                                   // '-a', 0.
+  int fixedvolume;                                                 // '-a', 0.
+  int regionattrib;                                                // '-A', 0.
+  int cdtrefine;                                                   // '-D', 0.
+  int insertaddpoints;                                             // '-i', 0.
+  int diagnose;                                                    // '-d', 0.
+  int convex;                                                      // '-c', 0.
+  int nomergefacet;                                                // '-M', 0.
+  int nomergevertex;                                               // '-M', 0.
+  int noexact;                                                     // '-X', 0.
+  int nostaticfilter;                                              // '-X', 0.
+  int zeroindex;                                                   // '-z', 0.
+  int facesout;                                                    // '-f', 0.
+  int edgesout;                                                    // '-e', 0.
+  int neighout;                                                    // '-n', 0.
+  int voroout;                                                     // '-v', 0.
+  int meditview;                                                   // '-g', 0.
+  int vtkview;                                                     // '-k', 0.
+  int nobound;                                                     // '-B', 0.
+  int nonodewritten;                                               // '-N', 0.
+  int noelewritten;                                                // '-E', 0.
+  int nofacewritten;                                               // '-F', 0.
+  int noiterationnum;                                              // '-I', 0.
+  int nojettison;                                                  // '-J', 0.
+  int docheck;                                                     // '-C', 0.
+  int quiet;                                                       // '-Q', 0.
+  int verbose;                                                     // '-V', 0.
+
+  // Parameters of TetGen. 
+  int vertexperblock;                                           // '-x', 4092.
+  int tetrahedraperblock;                                       // '-x', 8188.
+  int shellfaceperblock;                                        // '-x', 2044.
+  int nobisect_nomerge;                                            // '-Y', 1.
+  int supsteiner_level;                                           // '-Y/', 2.
+  int addsteiner_algo;                                           // '-Y//', 1.
+  int coarsen_param;                                               // '-R', 0.
+  int weighted_param;                                              // '-w', 0.
+  int fliplinklevel;                                                    // -1.
+  int flipstarsize;                                                     // -1.
+  int fliplinklevelinc;                                                 //  1.
+  int reflevel;                                                    // '-D', 3.
+  int optlevel;                                                    // '-O', 2.
+  int optscheme;                                                   // '-O', 7.
+  int delmaxfliplevel;                                                   // 1.
+  int order;                                                       // '-o', 1.
+  int reversetetori;                                              // '-o/', 0.
+  int steinerleft;                                                 // '-S', 0.
+  int no_sort;                                                           // 0.
+  int hilbert_order;                                           // '-b///', 52.
+  int hilbert_limit;                                             // '-b//'  8.
+  int brio_threshold;                                              // '-b' 64.
+  REAL brio_ratio;                                             // '-b/' 0.125.
+  REAL facet_separate_ang_tol;                                 // '-p', 179.9.
+  REAL facet_overlap_ang_tol;                                  // '-p/',  0.1.
+  REAL facet_small_ang_tol;                                   // '-p//', 15.0.
+  REAL maxvolume;                                               // '-a', -1.0.
+  REAL minratio;                                                 // '-q', 0.0.
+  REAL mindihedral;                                              // '-q', 5.0.
+  REAL optmaxdihedral;                                               // 165.0.
+  REAL optminsmtdihed;                                               // 179.0.
+  REAL optminslidihed;                                               // 179.0.  
+  REAL epsilon;                                               // '-T', 1.0e-8.
+  REAL coarsen_percent;                                         // -R1/#, 1.0.
+
+  // Strings of command line arguments and input/output file names.
+  char commandline[1024];
+  char infilename[1024];
+  char outfilename[1024];
+  char addinfilename[1024];
+  char bgmeshfilename[1024];
+
+  // The input object of TetGen. They are recognized by either the input 
+  //   file extensions or by the specified options. 
+  // Currently the following objects are supported:
+  //   - NODES, a list of nodes (.node); 
+  //   - POLY, a piecewise linear complex (.poly or .smesh); 
+  //   - OFF, a polyhedron (.off, Geomview's file format); 
+  //   - PLY, a polyhedron (.ply, file format from gatech, only ASCII);
+  //   - STL, a surface mesh (.stl, stereolithography format);
+  //   - MEDIT, a surface mesh (.mesh, Medit's file format); 
+  //   - MESH, a tetrahedral mesh (.ele).
+  // If no extension is available, the imposed command line switch
+  //   (-p or -r) implies the object. 
+  enum objecttype {NODES, POLY, OFF, PLY, STL, MEDIT, VTK, MESH} object;
+
+
+  void syntax();
+  void usage();
+
+  // Command line parse routine.
+  bool parse_commandline(int argc, char **argv);
+  bool parse_commandline(char *switches) {
+    return parse_commandline(0, &switches);
+  }
+
+  // Initialize all variables.
+  tetgenbehavior()
+  {
+    plc = 0;
+    psc = 0;
+    refine = 0;
+    quality = 0;
+    nobisect = 0;
+    coarsen = 0;
+    metric = 0;
+    weighted = 0;
+    brio_hilbert = 1;
+    incrflip = 0;
+    flipinsert = 0;
+    varvolume = 0;
+    fixedvolume = 0;
+    noexact = 0;
+    nostaticfilter = 0;
+    insertaddpoints = 0;
+    regionattrib = 0;
+    cdtrefine = 0;
+    diagnose = 0;
+    convex = 0;
+    zeroindex = 0;
+    facesout = 0;
+    edgesout = 0;
+    neighout = 0;
+    voroout = 0;
+    meditview = 0;
+    vtkview = 0;
+    nobound = 0;
+    nonodewritten = 0;
+    noelewritten = 0;
+    nofacewritten = 0;
+    noiterationnum = 0;
+    nomergefacet = 0;
+    nomergevertex = 0;
+    nojettison = 0;
+    docheck = 0;
+    quiet = 0;
+    verbose = 0;
+
+    vertexperblock = 4092;
+    tetrahedraperblock = 8188;
+    shellfaceperblock = 4092;
+    nobisect_nomerge = 1;
+    supsteiner_level = 2;
+    addsteiner_algo = 1;
+    coarsen_param = 0;
+    weighted_param = 0;
+    fliplinklevel = -1; 
+    flipstarsize = -1;  
+    fliplinklevelinc = 1;
+    reflevel = 3;
+    optscheme = 7;  
+    optlevel = 2;
+    delmaxfliplevel = 1;
+    order = 1;
+    reversetetori = 0;
+    steinerleft = -1;
+    no_sort = 0;
+    hilbert_order = 52; //-1;
+    hilbert_limit = 8;
+    brio_threshold = 64;
+    brio_ratio = 0.125;
+    facet_separate_ang_tol = 179.9;
+    facet_overlap_ang_tol = 0.1;
+    facet_small_ang_tol = 15.0;
+    maxvolume = -1.0;
+    minratio = 2.0;
+    mindihedral = 0.0;
+    optmaxdihedral = 165.00;
+    optminsmtdihed = 179.00;
+    optminslidihed = 179.00;
+    epsilon = 1.0e-8;
+    coarsen_percent = 1.0;
+    object = NODES;
+
+    commandline[0] = '\0';
+    infilename[0] = '\0';
+    outfilename[0] = '\0';
+    addinfilename[0] = '\0';
+    bgmeshfilename[0] = '\0';
+
+  }
+
+}; // class tetgenbehavior
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// tetgenmesh                                                                //
+//                                                                           //
+// A structure for creating and updating tetrahedral meshes.                 //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+class tetgenmesh {
+
+public:
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Mesh data structure                                                       //
+//                                                                           //
+// A tetrahedral mesh T of a 3D piecewise linear complex (PLC) X is a 3D     //
+// simplicial complex whose underlying space is equal to the space of X.  T  //
+// contains a 2D subcomplex S which is a triangular mesh of the boundary of  //
+// X. S contains a 1D subcomplex L which is a linear mesh of the boundary of //
+// S. Faces and edges in S and L are respectively called subfaces and segme- //
+// nts to distinguish them from others in T.                                 //
+//                                                                           //
+// TetGen stores the tetrahedra and vertices of T. The basic structure of a  //
+// tetrahedron contains pointers to its vertices and adjacent tetrahedra. A  //
+// vertex stores its x-, y-, and z-coordinates, and a pointer to a tetrahed- //
+// ron containing it. Both tetrahedra and vertices may contain user data.    // 
+//                                                                           //
+// Each face of T belongs to either two tetrahedra or one tetrahedron. In    //
+// the latter case, the face is an exterior boundary face of T.  TetGen adds //
+// fictitious tetrahedra (one-to-one) at such faces, and connects them to an //
+// "infinite vertex" (which has no geometric coordinates).  One can imagine  //
+// such a vertex lies in 4D space and is visible by all exterior boundary    //
+// faces.  The extended set of tetrahedra (including the infinite vertex) is //
+// a tetrahedralization of a 3-pseudomanifold without boundary.  It has the  //
+// property that every face is shared by exactly two tetrahedra.             // 
+//                                                                           //
+// The current version of TetGen stores explicitly the subfaces and segments //
+// (which are in surface mesh S and the linear mesh L), respectively.  Extra //
+// pointers are allocated in tetrahedra and subfaces to point each others.   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  // The tetrahedron data structure.  It includes the following fields:
+  //   - a list of four adjoining tetrahedra;
+  //   - a list of four vertices;
+  //   - a pointer to a list of four subfaces (optional, for -p switch);
+  //   - a pointer to a list of six segments  (optional, for -p switch);
+  //   - a list of user-defined floating-point attributes (optional);
+  //   - a volume constraint (optional, for -a switch);
+  //   - an integer of element marker (and flags);
+  // The structure of a tetrahedron is an array of pointers.  Its actual size
+  //   (the length of the array) is determined at runtime.
+
+  typedef REAL **tetrahedron;
+
+  // The subface data structure.  It includes the following fields:
+  //   - a list of three adjoining subfaces;
+  //   - a list of three vertices;
+  //   - a list of three adjoining segments;
+  //   - two adjoining tetrahedra;
+  //   - an area constraint (optional, for -q switch);
+  //   - an integer for boundary marker;
+  //   - an integer for type, flags, etc.
+
+  typedef REAL **shellface;
+
+  // The point data structure.  It includes the following fields:
+  //   - x, y and z coordinates;
+  //   - a list of user-defined point attributes (optional);
+  //   - u, v coordinates (optional, for -s switch);
+  //   - a metric tensor (optional, for -q or -m switch);
+  //   - a pointer to an adjacent tetrahedron;
+  //   - a pointer to a parent (or a duplicate) point;
+  //   - a pointer to an adjacent subface or segment (optional, -p switch);
+  //   - a pointer to a tet in background mesh (optional, for -m switch);
+  //   - an integer for boundary marker (point index);
+  //   - an integer for point type (and flags).
+  //   - an integer for geometry tag (optional, for -s switch).
+  // The structure of a point is an array of REALs.  Its acutal size is 
+  //   determined at the runtime.
+
+  typedef REAL *point;
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Handles                                                                   //
+//                                                                           //
+// Navigation and manipulation in a tetrahedralization are accomplished by   //
+// operating on structures referred as ``handles". A handle is a pair (t,v), //
+// where t is a pointer to a tetrahedron, and v is a 4-bit integer, in the   //
+// range from 0 to 11. v is called the ``version'' of a tetrahedron, it rep- //
+// resents a directed edge of a specific face of the tetrahedron.            //
+//                                                                           //
+// There are 12 even permutations of the four vertices, each of them corres- //
+// ponds to a directed edge (a version) of the tetrahedron.  The 12 versions //
+// can be grouped into 4 distinct ``edge rings'' in 4 ``oriented faces'' of  //
+// this tetrahedron.  One can encode each version (a directed edge) into a   //
+// 4-bit integer such that the two upper bits encode the index (from 0 to 2) //
+// of this edge in the edge ring, and the two lower bits encode the index (  //
+// from 0 to 3) of the oriented face which contains this edge.               //  
+//                                                                           //
+// The four vertices of a tetrahedron are indexed from 0 to 3 (according to  //
+// their storage in the data structure).  Give each face the same index as   //
+// the node opposite it in the tetrahedron.  Denote the edge connecting face //
+// i to face j as i/j. We number the twelve versions as follows:             //
+//                                                                           //
+//           |   edge 0     edge 1     edge 2                                //
+//   --------|--------------------------------                               //
+//    face 0 |   0 (0/1)    4 (0/3)    8 (0/2)                               //
+//    face 1 |   1 (1/2)    5 (1/3)    9 (1/0)                               //
+//    face 2 |   2 (2/3)    6 (2/1)   10 (2/0)                               //
+//    face 3 |   3 (3/0)    7 (3/1)   11 (3/2)                               //
+//                                                                           //
+// Similarly, navigation and manipulation in a (boundary) triangulation are  //
+// done by using handles of triangles. Each handle is a pair (s, v), where s //
+// is a pointer to a triangle, and v is a version in the range from 0 to 5.  //
+// Each version corresponds to a directed edge of this triangle.             //
+//                                                                           //
+// Number the three vertices of a triangle from 0 to 2 (according to their   //
+// storage in the data structure). Give each edge the same index as the node //
+// opposite it in the triangle. The six versions of a triangle are:          //
+//                                                                           //
+//                 | edge 0   edge 1   edge 2                                //
+//  ---------------|--------------------------                               //
+//   ccw orieation |   0        2        4                                   //
+//    cw orieation |   1        3        5                                   //
+//                                                                           //
+// In the following, a 'triface' is a handle of tetrahedron, and a 'face' is //
+// a handle of a triangle.                                                   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  class triface {
+  public:
+    tetrahedron *tet;
+    int ver; // Range from 0 to 11.
+    triface() : tet(0), ver(0) {}
+    triface& operator=(const triface& t) {
+      tet = t.tet; ver = t.ver;
+      return *this;
+    }
+  };
+
+  class face {
+  public:
+    shellface *sh;
+    int shver; // Range from 0 to 5.
+    face() : sh(0), shver(0) {}
+    face& operator=(const face& s) {
+      sh = s.sh; shver = s.shver;
+      return *this;
+    }
+  };
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Arraypool                                                                 //
+//                                                                           //
+// A dynamic linear array. (It is written by J. Shewchuk)                    //
+//                                                                           //
+// Each arraypool contains an array of pointers to a number of blocks.  Each //
+// block contains the same fixed number of objects.  Each index of the array //
+// addresses a particular object in the pool. The most significant bits add- //
+// ress the index of the block containing the object. The less significant   //
+// bits address this object within the block.                                //
+//                                                                           //
+// 'objectbytes' is the size of one object in blocks; 'log2objectsperblock'  //
+// is the base-2 logarithm of 'objectsperblock'; 'objects' counts the number //
+// of allocated objects; 'totalmemory' is the total memory in bytes.         //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  class arraypool {
+
+  public:
+
+    int objectbytes;
+    int objectsperblock;
+    int log2objectsperblock;
+    int objectsperblockmark;
+    int toparraylen;
+    char **toparray;
+    long objects;
+    unsigned long totalmemory;
+
+    void restart();
+    void poolinit(int sizeofobject, int log2objperblk);
+    char* getblock(int objectindex);
+    void* lookup(int objectindex);
+    int newindex(void **newptr);
+
+    arraypool(int sizeofobject, int log2objperblk);
+    ~arraypool();
+  };
+
+// fastlookup() -- A fast, unsafe operation. Return the pointer to the object
+//   with a given index.  Note: The object's block must have been allocated,
+//   i.e., by the function newindex().
+
+#define fastlookup(pool, index) \
+  (void *) ((pool)->toparray[(index) >> (pool)->log2objectsperblock] + \
+            ((index) & (pool)->objectsperblockmark) * (pool)->objectbytes)
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Memorypool                                                                //
+//                                                                           //
+// A structure for memory allocation. (It is written by J. Shewchuk)         //
+//                                                                           //
+// firstblock is the first block of items. nowblock is the block from which  //
+//   items are currently being allocated. nextitem points to the next slab   //
+//   of free memory for an item. deaditemstack is the head of a linked list  //
+//   (stack) of deallocated items that can be recycled.  unallocateditems is //
+//   the number of items that remain to be allocated from nowblock.          //
+//                                                                           //
+// Traversal is the process of walking through the entire list of items, and //
+//   is separate from allocation.  Note that a traversal will visit items on //
+//   the "deaditemstack" stack as well as live items.  pathblock points to   //
+//   the block currently being traversed.  pathitem points to the next item  //
+//   to be traversed.  pathitemsleft is the number of items that remain to   //
+//   be traversed in pathblock.                                              //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  class memorypool {
+
+  public:
+
+    void **firstblock, **nowblock;
+    void *nextitem;
+    void *deaditemstack;
+    void **pathblock;
+    void *pathitem;
+    int  alignbytes;
+    int  itembytes, itemwords;
+    int  itemsperblock;
+    long items, maxitems;
+    int  unallocateditems;
+    int  pathitemsleft;
+
+    memorypool();
+    memorypool(int, int, int, int);
+    ~memorypool();
+    
+    void poolinit(int, int, int, int);
+    void restart();
+    void *alloc();
+    void dealloc(void*);
+    void traversalinit();
+    void *traverse();
+  };  
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// badface                                                                   //
+//                                                                           //
+// Despite of its name, a 'badface' can be used to represent one of the      //
+// following objects:                                                        //
+//   - a face of a tetrahedron which is (possibly) non-Delaunay;             //
+//   - an encroached subsegment or subface;                                  //
+//   - a bad-quality tetrahedron, i.e, has too large radius-edge ratio;      //
+//   - a sliver, i.e., has good radius-edge ratio but nearly zero volume;    //
+//   - a recently flipped face (saved for undoing the flip later).           //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  class badface {
+  public:
+    triface tt; 
+    face ss;
+    REAL key, cent[6];  // circumcenter or cos(dihedral angles) at 6 edges.
+    point forg, fdest, fapex, foppo, noppo;
+    badface *nextitem; 
+    badface() : key(0), forg(0), fdest(0), fapex(0), foppo(0), noppo(0),
+      nextitem(0) {}
+  };
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// insertvertexflags                                                         //
+//                                                                           //
+// A collection of flags that pass to the routine insertvertex().            //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  class insertvertexflags {
+
+  public:
+
+    int iloc;  // input/output.
+    int bowywat, lawson;
+    int splitbdflag, validflag, respectbdflag;
+    int rejflag, chkencflag, cdtflag;
+    int assignmeshsize;
+    int sloc, sbowywat;
+
+    // Used by Delaunay refinement.
+    int refineflag; // 0, 1, 2, 3
+    triface refinetet;
+    face refinesh;
+    int smlenflag; // for useinsertradius.
+    REAL smlen; // for useinsertradius.
+    point parentpt;
+
+    insertvertexflags() {
+      iloc = bowywat = lawson = 0;
+      splitbdflag = validflag = respectbdflag = 0;
+      rejflag = chkencflag = cdtflag = 0;
+      assignmeshsize = 0;
+      sloc = sbowywat = 0;
+
+      refineflag = 0;
+      refinetet.tet = NULL;
+      refinesh.sh = NULL;
+      smlenflag = 0;
+      smlen = 0.0;
+    }
+  };
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// flipconstraints                                                           //
+//                                                                           //
+// A structure of a collection of data (options and parameters) which pass   //
+// to the edge flip function flipnm().                                       //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  class flipconstraints {
+
+  public:
+
+    // Elementary flip flags.
+    int enqflag; // (= flipflag)
+    int chkencflag;
+
+    // Control flags
+    int unflip;  // Undo the performed flips.
+    int collectnewtets; // Collect the new tets created by flips.
+    int collectencsegflag;
+
+    // Optimization flags.
+    int remove_ndelaunay_edge; // Remove a non-Delaunay edge.
+    REAL bak_tetprism_vol; // The value to be minimized.
+    REAL tetprism_vol_sum;
+    int remove_large_angle; // Remove a large dihedral angle at edge.
+    REAL cosdihed_in; // The input cosine of the dihedral angle (> 0).
+    REAL cosdihed_out; // The improved cosine of the dihedral angle.
+
+    // Boundary recovery flags.
+    int checkflipeligibility;
+    point seg[2];  // A constraining edge to be recovered.
+    point fac[3];  // A constraining face to be recovered.
+    point remvert; // A vertex to be removed.
+
+
+    flipconstraints() {
+      enqflag = 0; 
+      chkencflag = 0;
+
+      unflip = 0;
+      collectnewtets = 0;
+      collectencsegflag = 0;
+
+      remove_ndelaunay_edge = 0;
+      bak_tetprism_vol = 0.0;
+      tetprism_vol_sum = 0.0;
+      remove_large_angle = 0;
+      cosdihed_in = 0.0;
+      cosdihed_out = 0.0;
+
+      checkflipeligibility = 0;
+      seg[0] = NULL;
+      fac[0] = NULL;
+      remvert = NULL;
+    }
+  };
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// optparameters                                                             //
+//                                                                           //
+// Optimization options and parameters.                                      //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  class optparameters {
+
+  public:
+
+    // The one of goals of optimization.
+    int max_min_volume;      // Maximize the minimum volume.
+	int min_max_aspectratio; // Minimize the maximum aspect ratio. 
+    int min_max_dihedangle;  // Minimize the maximum dihedral angle.
+
+    // The initial and improved value.
+    REAL initval, imprval;
+
+    int numofsearchdirs;
+    REAL searchstep;
+    int maxiter;  // Maximum smoothing iterations (disabled by -1).
+    int smthiter; // Performed iterations.
+
+
+    optparameters() {
+      max_min_volume = 0;
+      min_max_aspectratio = 0;
+      min_max_dihedangle = 0;
+
+      initval = imprval = 0.0;
+
+      numofsearchdirs = 10;
+      searchstep = 0.01;
+      maxiter = -1;   // Unlimited smoothing iterations.
+      smthiter = 0;
+
+    }
+  };
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Labels (enumeration declarations) used by TetGen.                         //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  // Labels that signify the type of a vertex. 
+  enum verttype {UNUSEDVERTEX, DUPLICATEDVERTEX, RIDGEVERTEX, ACUTEVERTEX,
+                 FACETVERTEX, VOLVERTEX, FREESEGVERTEX, FREEFACETVERTEX, 
+                 FREEVOLVERTEX, NREGULARVERTEX, DEADVERTEX};
+ 
+  // Labels that signify the result of triangle-triangle intersection test.
+  enum interresult {DISJOINT, INTERSECT, SHAREVERT, SHAREEDGE, SHAREFACE,
+                    TOUCHEDGE, TOUCHFACE, ACROSSVERT, ACROSSEDGE, ACROSSFACE};
+
+  // Labels that signify the result of point location.
+  enum locateresult {UNKNOWN, OUTSIDE, INTETRAHEDRON, ONFACE, ONEDGE, ONVERTEX,
+                     ENCVERTEX, ENCSEGMENT, ENCSUBFACE, NEARVERTEX, NONREGULAR,
+                     INSTAR, BADELEMENT};
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Variables of TetGen                                                       //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  // Pointer to the input data (a set of nodes, a PLC, or a mesh).
+  tetgenio *in, *addin;
+
+  // Pointer to the switches and parameters.
+  tetgenbehavior *b;
+
+  // Pointer to a background mesh (contains size specification map).
+  tetgenmesh *bgm;
+
+  // Memorypools to store mesh elements (points, tetrahedra, subfaces, and
+  //   segments) and extra pointers between tetrahedra, subfaces, and segments.
+  memorypool *tetrahedrons, *subfaces, *subsegs, *points;
+  memorypool *tet2subpool, *tet2segpool;
+
+  // Memorypools to store bad-quality (or encroached) elements.
+  memorypool *badtetrahedrons, *badsubfacs, *badsubsegs;
+
+  // A memorypool to store faces to be flipped.
+  memorypool *flippool;
+  arraypool *unflipqueue;
+  badface *flipstack; 
+
+  // Arrays used for point insertion (the Bowyer-Watson algorithm).
+  arraypool *cavetetlist, *cavebdrylist, *caveoldtetlist;
+  arraypool *cavetetshlist, *cavetetseglist, *cavetetvertlist;
+  arraypool *caveencshlist, *caveencseglist;
+  arraypool *caveshlist, *caveshbdlist, *cavesegshlist;
+
+  // Stacks used for CDT construction and boundary recovery.
+  arraypool *subsegstack, *subfacstack, *subvertstack;
+
+  // Arrays of encroached segments and subfaces (for mesh refinement).
+  arraypool *encseglist, *encshlist;
+
+  // The map between facets to their vertices (for mesh refinement).
+  int *idx2facetlist;
+  point *facetverticeslist;
+
+  // The map between segments to their endpoints (for mesh refinement).
+  point *segmentendpointslist;
+
+  // The infinite vertex.
+  point dummypoint;
+  // The recently visited tetrahedron, subface.
+  triface recenttet;
+  face recentsh;
+
+  // PI is the ratio of a circle's circumference to its diameter.
+  static REAL PI;
+
+  // Array (size = numberoftetrahedra * 6) for storing high-order nodes of
+  //   tetrahedra (only used when -o2 switch is selected).
+  point *highordertable;
+
+  // Various variables.
+  int numpointattrib;                          // Number of point attributes.
+  int numelemattrib;                     // Number of tetrahedron attributes.
+  int sizeoftensor;                     // Number of REALs per metric tensor.
+  int pointmtrindex;           // Index to find the metric tensor of a point.
+  int pointparamindex;       // Index to find the u,v coordinates of a point.
+  int point2simindex;         // Index to find a simplex adjacent to a point.
+  int pointmarkindex;            // Index to find boundary marker of a point.
+  int pointinsradiusindex;  // Index to find the insertion radius of a point.
+  int elemattribindex;          // Index to find attributes of a tetrahedron.
+  int volumeboundindex;       // Index to find volume bound of a tetrahedron.
+  int elemmarkerindex;              // Index to find marker of a tetrahedron.
+  int shmarkindex;             // Index to find boundary marker of a subface.
+  int areaboundindex;               // Index to find area bound of a subface.
+  int checksubsegflag;   // Are there segments in the tetrahedralization yet?
+  int checksubfaceflag;  // Are there subfaces in the tetrahedralization yet?
+  int checkconstraints;  // Are there variant (node, seg, facet) constraints?
+  int nonconvex;                               // Is current mesh non-convex?
+  int autofliplinklevel;        // The increase of link levels, default is 1.
+  int useinsertradius;       // Save the insertion radius for Steiner points.
+  long samples;               // Number of random samples for point location.
+  unsigned long randomseed;                    // Current random number seed.
+  REAL cosmaxdihed, cosmindihed;    // The cosine values of max/min dihedral.
+  REAL cossmtdihed;     // The cosine value of a bad dihedral to be smoothed.
+  REAL cosslidihed;      // The cosine value of the max dihedral of a sliver.
+  REAL minfaceang, minfacetdihed;     // The minimum input (dihedral) angles.
+  REAL tetprism_vol_sum;   // The total volume of tetrahedral-prisms (in 4D).
+  REAL longest;                          // The longest possible edge length.
+  REAL minedgelength;                               // = longest * b->epsion.
+  REAL xmax, xmin, ymax, ymin, zmax, zmin;         // Bounding box of points.
+
+  // Counters.
+  long insegments;                               // Number of input segments.
+  long hullsize;                        // Number of exterior boundary faces.
+  long meshedges;                                    // Number of mesh edges.
+  long meshhulledges;                       // Number of boundary mesh edges.
+  long steinerleft;                 // Number of Steiner points not yet used.
+  long dupverts;                            // Are there duplicated vertices?
+  long unuverts;                                // Are there unused vertices?
+  long nonregularcount;                    // Are there non-regular vertices?
+  long st_segref_count, st_facref_count, st_volref_count;  // Steiner points.
+  long fillregioncount, cavitycount, cavityexpcount;
+  long flip14count, flip26count, flipn2ncount;
+  long flip23count, flip32count, flip44count, flip41count;
+  long flip31count, flip22count;
+  unsigned long totalworkmemory;      // Total memory used by working arrays.
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Mesh manipulation primitives                                              //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  // Fast lookup tables for mesh manipulation primitives.
+  static int bondtbl[12][12], fsymtbl[12][12];
+  static int esymtbl[12], enexttbl[12], eprevtbl[12];
+  static int enextesymtbl[12], eprevesymtbl[12]; 
+  static int eorgoppotbl[12], edestoppotbl[12];
+  static int facepivot1[12], facepivot2[12][12];
+  static int orgpivot[12], destpivot[12], apexpivot[12], oppopivot[12];
+  static int tsbondtbl[12][6], stbondtbl[12][6];
+  static int tspivottbl[12][6], stpivottbl[12][6];
+  static int ver2edge[12], edge2ver[6], epivot[12];
+  static int sorgpivot [6], sdestpivot[6], sapexpivot[6];
+  static int snextpivot[6];
+
+  void inittables();
+
+  // Primitives for tetrahedra.
+  inline tetrahedron encode(triface& t);
+  inline tetrahedron encode2(tetrahedron* ptr, int ver);
+  inline void decode(tetrahedron ptr, triface& t);
+  inline void bond(triface& t1, triface& t2);
+  inline void dissolve(triface& t);
+  inline void esym(triface& t1, triface& t2);
+  inline void esymself(triface& t);
+  inline void enext(triface& t1, triface& t2);
+  inline void enextself(triface& t);
+  inline void eprev(triface& t1, triface& t2);
+  inline void eprevself(triface& t);
+  inline void enextesym(triface& t1, triface& t2);
+  inline void enextesymself(triface& t);
+  inline void eprevesym(triface& t1, triface& t2);
+  inline void eprevesymself(triface& t);
+  inline void eorgoppo(triface& t1, triface& t2);
+  inline void eorgoppoself(triface& t);
+  inline void edestoppo(triface& t1, triface& t2);
+  inline void edestoppoself(triface& t);
+  inline void fsym(triface& t1, triface& t2);
+  inline void fsymself(triface& t);
+  inline void fnext(triface& t1, triface& t2);
+  inline void fnextself(triface& t);
+  inline point org (triface& t);
+  inline point dest(triface& t);
+  inline point apex(triface& t);
+  inline point oppo(triface& t);
+  inline void setorg (triface& t, point p);
+  inline void setdest(triface& t, point p);
+  inline void setapex(triface& t, point p);
+  inline void setoppo(triface& t, point p);
+  inline REAL elemattribute(tetrahedron* ptr, int attnum);
+  inline void setelemattribute(tetrahedron* ptr, int attnum, REAL value);
+  inline REAL volumebound(tetrahedron* ptr);
+  inline void setvolumebound(tetrahedron* ptr, REAL value);
+  inline int  elemindex(tetrahedron* ptr);
+  inline void setelemindex(tetrahedron* ptr, int value);
+  inline int  elemmarker(tetrahedron* ptr);
+  inline void setelemmarker(tetrahedron* ptr, int value);
+  inline void infect(triface& t);
+  inline void uninfect(triface& t);
+  inline bool infected(triface& t);
+  inline void marktest(triface& t);
+  inline void unmarktest(triface& t);
+  inline bool marktested(triface& t);
+  inline void markface(triface& t);
+  inline void unmarkface(triface& t);
+  inline bool facemarked(triface& t);
+  inline void markedge(triface& t);
+  inline void unmarkedge(triface& t);
+  inline bool edgemarked(triface& t);
+  inline void marktest2(triface& t);
+  inline void unmarktest2(triface& t);
+  inline bool marktest2ed(triface& t);
+  inline int  elemcounter(triface& t);
+  inline void setelemcounter(triface& t, int value);
+  inline void increaseelemcounter(triface& t);
+  inline void decreaseelemcounter(triface& t);
+  inline bool ishulltet(triface& t);
+  inline bool isdeadtet(triface& t);
+ 
+  // Primitives for subfaces and subsegments.
+  inline void sdecode(shellface sptr, face& s);
+  inline shellface sencode(face& s);
+  inline shellface sencode2(shellface *sh, int shver);
+  inline void spivot(face& s1, face& s2);
+  inline void spivotself(face& s);
+  inline void sbond(face& s1, face& s2);
+  inline void sbond1(face& s1, face& s2);
+  inline void sdissolve(face& s);
+  inline point sorg(face& s);
+  inline point sdest(face& s);
+  inline point sapex(face& s);
+  inline void setsorg(face& s, point pointptr);
+  inline void setsdest(face& s, point pointptr);
+  inline void setsapex(face& s, point pointptr);
+  inline void sesym(face& s1, face& s2);
+  inline void sesymself(face& s);
+  inline void senext(face& s1, face& s2);
+  inline void senextself(face& s);
+  inline void senext2(face& s1, face& s2);
+  inline void senext2self(face& s);
+  inline REAL areabound(face& s);
+  inline void setareabound(face& s, REAL value);
+  inline int shellmark(face& s);
+  inline void setshellmark(face& s, int value);
+  inline void sinfect(face& s);
+  inline void suninfect(face& s);
+  inline bool sinfected(face& s);
+  inline void smarktest(face& s);
+  inline void sunmarktest(face& s);
+  inline bool smarktested(face& s);
+  inline void smarktest2(face& s);
+  inline void sunmarktest2(face& s);
+  inline bool smarktest2ed(face& s);
+  inline void smarktest3(face& s);
+  inline void sunmarktest3(face& s);
+  inline bool smarktest3ed(face& s);
+  inline void setfacetindex(face& f, int value);
+  inline int  getfacetindex(face& f);
+
+  // Primitives for interacting tetrahedra and subfaces.
+  inline void tsbond(triface& t, face& s);
+  inline void tsdissolve(triface& t);
+  inline void stdissolve(face& s);
+  inline void tspivot(triface& t, face& s);
+  inline void stpivot(face& s, triface& t);
+
+  // Primitives for interacting tetrahedra and segments.
+  inline void tssbond1(triface& t, face& seg);
+  inline void sstbond1(face& s, triface& t);
+  inline void tssdissolve1(triface& t);
+  inline void sstdissolve1(face& s);
+  inline void tsspivot1(triface& t, face& s);
+  inline void sstpivot1(face& s, triface& t);
+
+  // Primitives for interacting subfaces and segments.
+  inline void ssbond(face& s, face& edge);
+  inline void ssbond1(face& s, face& edge);
+  inline void ssdissolve(face& s);
+  inline void sspivot(face& s, face& edge);
+
+  // Primitives for points.
+  inline int  pointmark(point pt);
+  inline void setpointmark(point pt, int value);
+  inline enum verttype pointtype(point pt);
+  inline void setpointtype(point pt, enum verttype value);
+  inline int  pointgeomtag(point pt);
+  inline void setpointgeomtag(point pt, int value);
+  inline REAL pointgeomuv(point pt, int i);
+  inline void setpointgeomuv(point pt, int i, REAL value);
+  inline void pinfect(point pt);
+  inline void puninfect(point pt);
+  inline bool pinfected(point pt);
+  inline void pmarktest(point pt);
+  inline void punmarktest(point pt);
+  inline bool pmarktested(point pt);
+  inline void pmarktest2(point pt);
+  inline void punmarktest2(point pt);
+  inline bool pmarktest2ed(point pt);
+  inline void pmarktest3(point pt);
+  inline void punmarktest3(point pt);
+  inline bool pmarktest3ed(point pt);
+  inline tetrahedron point2tet(point pt);
+  inline void setpoint2tet(point pt, tetrahedron value);
+  inline shellface point2sh(point pt);
+  inline void setpoint2sh(point pt, shellface value);
+  inline point point2ppt(point pt);
+  inline void setpoint2ppt(point pt, point value);
+  inline tetrahedron point2bgmtet(point pt);
+  inline void setpoint2bgmtet(point pt, tetrahedron value);
+  inline void setpointinsradius(point pt, REAL value);
+  inline REAL getpointinsradius(point pt);
+  inline bool issteinerpoint(point pt);
+
+  // Advanced primitives.
+  inline void point2tetorg(point pt, triface& t);
+  inline void point2shorg(point pa, face& s);
+  inline point farsorg(face& seg);
+  inline point farsdest(face& seg);
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+//  Memory managment                                                         //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  void tetrahedrondealloc(tetrahedron*);
+  tetrahedron *tetrahedrontraverse();
+  tetrahedron *alltetrahedrontraverse();
+  void shellfacedealloc(memorypool*, shellface*);
+  shellface *shellfacetraverse(memorypool*);
+  void pointdealloc(point);
+  point pointtraverse();
+
+  void makeindex2pointmap(point*&);
+  void makepoint2submap(memorypool*, int*&, face*&);
+  void maketetrahedron(triface*);
+  void makeshellface(memorypool*, face*);
+  void makepoint(point*, enum verttype);
+
+  void initializepools();
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Advanced geometric predicates and calculations                            //
+//                                                                           //
+// TetGen uses a simplified symbolic perturbation scheme from Edelsbrunner,  //
+// et al [*].  Hence the point-in-sphere test never returns a zero. The idea //
+// is to perturb the weights of vertices in the fourth dimension.  TetGen    //
+// uses the indices of the vertices decide the amount of perturbation. It is //
+// implemented in the routine insphere_s().
+//                                                                           //
+// The routine tri_edge_test() determines whether or not a triangle and an   //
+// edge intersect in 3D. If they intersect, their intersection type is also  //
+// reported. This test is a combination of n 3D orientation tests (n is bet- //
+// ween 3 and 9). It uses the robust orient3d() test to make the branch dec- //
+// isions.  The routine tri_tri_test() determines whether or not two triang- //
+// les intersect in 3D. It also uses the robust orient3d() test.             //
+//                                                                           //
+// There are a number of routines to calculate geometrical quantities, e.g., //
+// circumcenters, angles, dihedral angles, face normals, face areas, etc.    //
+// They are so far done by the default floating-point arithmetics which are  //
+// non-robust. They should be improved in the future.                        //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  // Symbolic perturbations (robust)
+  REAL insphere_s(REAL*, REAL*, REAL*, REAL*, REAL*);
+  REAL orient4d_s(REAL*, REAL*, REAL*, REAL*, REAL*, 
+                  REAL, REAL, REAL, REAL, REAL);
+
+  // Triangle-edge intersection test (robust)
+  int tri_edge_2d(point, point, point, point, point, point, int, int*, int*);
+  int tri_edge_tail(point, point, point, point, point, point, REAL, REAL, int,
+                    int*, int*);
+  int tri_edge_test(point, point, point, point, point, point, int, int*, int*);
+
+  // Triangle-triangle intersection test (robust)
+  int tri_edge_inter_tail(point, point, point, point, point, REAL, REAL);
+  int tri_tri_inter(point, point, point, point, point, point);
+
+  // Linear algebra functions
+  inline REAL dot(REAL* v1, REAL* v2);
+  inline void cross(REAL* v1, REAL* v2, REAL* n);
+  bool lu_decmp(REAL lu[4][4], int n, int* ps, REAL* d, int N);
+  void lu_solve(REAL lu[4][4], int n, int* ps, REAL* b, int N);
+
+  // An embedded 2-dimensional geometric predicate (non-robust)
+  REAL incircle3d(point pa, point pb, point pc, point pd);
+
+  // Geometric calculations (non-robust)
+  REAL orient3dfast(REAL *pa, REAL *pb, REAL *pc, REAL *pd);
+  inline REAL norm2(REAL x, REAL y, REAL z);
+  inline REAL distance(REAL* p1, REAL* p2);
+  void facenormal(point pa, point pb, point pc, REAL *n, int pivot, REAL *lav);
+  REAL shortdistance(REAL* p, REAL* e1, REAL* e2);
+  REAL triarea(REAL* pa, REAL* pb, REAL* pc);
+  REAL interiorangle(REAL* o, REAL* p1, REAL* p2, REAL* n);
+  void projpt2edge(REAL* p, REAL* e1, REAL* e2, REAL* prj);
+  void projpt2face(REAL* p, REAL* f1, REAL* f2, REAL* f3, REAL* prj);
+  bool tetalldihedral(point, point, point, point, REAL*, REAL*, REAL*);
+  void tetallnormal(point, point, point, point, REAL N[4][3], REAL* volume);
+  REAL tetaspectratio(point, point, point, point);
+  bool circumsphere(REAL*, REAL*, REAL*, REAL*, REAL* cent, REAL* radius);
+  bool orthosphere(REAL*,REAL*,REAL*,REAL*,REAL,REAL,REAL,REAL,REAL*,REAL*);
+  void planelineint(REAL*, REAL*, REAL*, REAL*, REAL*, REAL*, REAL*);
+  int linelineint(REAL*, REAL*, REAL*, REAL*, REAL*, REAL*, REAL*, REAL*);
+  REAL tetprismvol(REAL* pa, REAL* pb, REAL* pc, REAL* pd);
+  bool calculateabovepoint(arraypool*, point*, point*, point*);
+  void calculateabovepoint4(point, point, point, point);
+
+  // PLC error reports.
+  void report_overlapping_facets(face*, face*, REAL dihedang = 0.0);
+  int report_selfint_edge(point, point, face* sedge, triface* searchtet, 
+                          enum interresult);
+  int report_selfint_face(point, point, point, face* sface, triface* iedge, 
+                          int intflag, int* types, int* poss);
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Local mesh transformations                                                //
+//                                                                           //
+// A local transformation replaces a small set of tetrahedra with another    //
+// set of tetrahedra which fills the same space and the same boundaries.     //
+//   In 3D, the most simplest local transformations are the elementary flips //
+// performed within the convex hull of five vertices: 2-to-3, 3-to-2, 1-to-4,//
+// and 4-to-1 flips,  where the numbers indicate the number of tetrahedra    //
+// before and after each flip.  The 1-to-4 and 4-to-1 flip involve inserting //
+// or deleting a vertex, respectively.                                       //
+//   There are complex local transformations which can be decomposed as a    //
+// combination of elementary flips. For example,a 4-to-4 flip which replaces //
+// two coplanar edges can be regarded by a 2-to-3 flip and a 3-to-2 flip.    //
+// Note that the first 2-to-3 flip will temporarily create a degenerate tet- //
+// rahedron which is removed immediately by the followed 3-to-2 flip.  More  //
+// generally, a n-to-m flip, where n > 3, m = (n - 2) * 2, which removes an  //
+// edge can be done by first performing a sequence of (n - 3) 2-to-3 flips   //
+// followed by a 3-to-2 flip.                                                //
+//                                                                           //
+// The routines flip23(), flip32(), and flip41() perform the three element-  //
+// ray flips. The flip14() is available inside the routine insertpoint().    //
+//                                                                           //
+// The routines flipnm() and flipnm_post() implement a generalized edge flip //
+// algorithm which uses a combination of elementary flips.                   //
+//                                                                           //
+// The routine insertpoint() implements a variant of Bowyer-Watson's cavity  //
+// algorithm to insert a vertex. It works for arbitrary tetrahedralization,  //
+// either Delaunay, or constrained Delaunay, or non-Delaunay.                //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  // The elementary flips.
+  void flip23(triface*, int, flipconstraints* fc);
+  void flip32(triface*, int, flipconstraints* fc);
+  void flip41(triface*, int, flipconstraints* fc);
+
+  // A generalized edge flip.
+  int flipnm(triface*, int n, int level, int, flipconstraints* fc);
+  int flipnm_post(triface*, int n, int nn, int, flipconstraints* fc);
+
+  // Point insertion.
+  int  insertpoint(point, triface*, face*, face*, insertvertexflags*);
+  void insertpoint_abort(face*, insertvertexflags*);
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Delaunay tetrahedralization                                               //
+//                                                                           //
+// The routine incrementaldelaunay() implemented two incremental algorithms  //
+// for constructing Delaunay tetrahedralizations (DTs):  the Bowyer-Watson   //
+// (B-W) algorithm and the incremental flip algorithm of Edelsbrunner and    //
+// Shah, "Incremental topological flipping works for regular triangulation," //
+// Algorithmica, 15:233-241, 1996.                                           //
+//                                                                           //
+// The routine incrementalflip() implements the flip algorithm of [Edelsbru- //
+// nner and Shah, 1996].  It flips a queue of locally non-Delaunay faces (in //
+// an arbitrary order).  The success is guaranteed when the Delaunay tetrah- //
+// edralization is constructed incrementally by adding one vertex at a time. //
+//                                                                           //
+// The routine locate() finds a tetrahedron contains a new point in current  //
+// DT.  It uses a simple stochastic walk algorithm: starting from an arbitr- //
+// ary tetrahedron in DT, it finds the destination by visit one tetrahedron  //
+// at a time, randomly chooses a tetrahedron if there are more than one      //
+// choices. This algorithm terminates due to Edelsbrunner's acyclic theorem. //
+//   Choose a good starting tetrahedron is crucial to the speed of the walk. //
+// TetGen originally uses the "jump-and-walk" algorithm of Muecke, E.P.,     //
+// Saias, I., and Zhu, B. "Fast Randomized Point Location Without Preproces- //
+// sing." In Proceedings of the 12th ACM Symposium on Computational Geometry,//
+// 274-283, 1996.  It first randomly samples several tetrahedra in the DT    //
+// and then choosing the closet one to start walking.                        //
+//   The above algorithm slows download dramatically as the number of points //
+// grows -- reported in Amenta, N., Choi, S. and Rote, G., "Incremental      //
+// construction con {BRIO}," In Proceedings of 19th ACM Symposium on         //
+// Computational Geometry, 211-219, 2003.  On the other hand, Liu and        //
+// Snoeyink showed that the point location can be made in constant time if   //
+// the points are pre-sorted so that the nearby points in space have nearby  //
+// indices, then adding the points in this order. They sorted the points     //
+// along the 3D Hilbert curve.                                               //
+//                                                                           //
+// The routine hilbert_sort3() sorts a set of 3D points along the 3D Hilbert //
+// curve. It recursively splits a point set according to the Hilbert indices //
+// mapped to the subboxes of the bounding box of the point set.              //
+//   The Hilbert indices is calculated by Butz's algorithm in 1971.  A nice  //
+// exposition of this algorithm can be found in the paper of Hamilton, C.,   //
+// "Compact Hilbert Indices", Technical Report CS-2006-07, Computer Science, //
+// Dalhousie University, 2006 (the Section 2). My implementation also refer- //
+// enced Steven Witham's implementation of "Hilbert walk" (hopefully, it is  //
+// still available at: http://www.tiac.net/~sw/2008/10/Hilbert/).            //
+//                                                                           //
+// TetGen sorts the points using the method in the paper of Boissonnat,J.-D.,//
+// Devillers, O. and Hornus, S. "Incremental Construction of the Delaunay    //
+// Triangulation and the Delaunay Graph in Medium Dimension," In Proceedings //
+// of the 25th ACM Symposium on Computational Geometry, 2009.                //
+//   It first randomly sorts the points into subgroups using the Biased Rand-//
+// omized Insertion Ordering (BRIO) of Amenta et al 2003, then sorts the     //
+// points in each subgroup along the 3D Hilbert curve.  Inserting points in  //
+// this order ensures a randomized "sprinkling" of the points over the       //
+// domain, while sorting of each subset ensures locality.                    //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  void transfernodes();
+
+  // Point sorting.
+  int  transgc[8][3][8], tsb1mod3[8];
+  void hilbert_init(int n);
+  int  hilbert_split(point* vertexarray, int arraysize, int gc0, int gc1,
+                     REAL, REAL, REAL, REAL, REAL, REAL);
+  void hilbert_sort3(point* vertexarray, int arraysize, int e, int d,
+                     REAL, REAL, REAL, REAL, REAL, REAL, int depth);
+  void brio_multiscale_sort(point*,int,int threshold,REAL ratio,int* depth);
+
+  // Point location.
+  unsigned long randomnation(unsigned int choices);
+  void randomsample(point searchpt, triface *searchtet);
+  enum locateresult locate(point searchpt, triface *searchtet, 
+                           int chkencflag = 0);
+
+  // Incremental flips.
+  void flippush(badface*&, triface*);
+  int  incrementalflip(point newpt, int, flipconstraints *fc);
+
+  // Incremental Delaunay construction.
+  void initialdelaunay(point pa, point pb, point pc, point pd);
+  void incrementaldelaunay(clock_t&);
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Surface triangulation                                                     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  void flipshpush(face*);
+  void flip22(face*, int, int);
+  void flip31(face*, int);
+  long lawsonflip();
+  int sinsertvertex(point newpt, face*, face*, int iloc, int bowywat, int);
+  int sremovevertex(point delpt, face*, face*, int lawson);
+
+  enum locateresult slocate(point, face*, int, int, int);
+  enum interresult sscoutsegment(face*, point, int, int, int);
+  void scarveholes(int, REAL*);
+
+  void unifysegments();
+  void identifyinputedges(point*);
+  void mergefacets();
+
+  enum interresult finddirection(triface* searchtet, point endpt);
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Constrained tetrahedralizations.                                          //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  int checkflipeligibility(int fliptype, point, point, point, point, point,
+                           int level, int edgepivot, flipconstraints* fc);
+
+  int removeedgebyflips(triface*, flipconstraints*);
+  int removefacebyflips(triface*, flipconstraints*);
+
+  int recoveredgebyflips(point, point, face*, triface*, int fullsearch);
+  int add_steinerpt_in_schoenhardtpoly(triface*, int, int chkencflag);
+  int add_steinerpt_in_segment(face*, int searchlevel); 
+  int addsteiner4recoversegment(face*, int);
+  int recoversegments(arraypool*, int fullsearch, int steinerflag);
+
+  int recoverfacebyflips(point, point, point, face*, triface*);
+  int recoversubfaces(arraypool*, int steinerflag);
+
+  int getvertexstar(int, point searchpt, arraypool*, arraypool*, arraypool*);
+  int getedge(point, point, triface*);
+  int reduceedgesatvertex(point startpt, arraypool* endptlist);
+  int removevertexbyflips(point steinerpt);
+
+  int suppressbdrysteinerpoint(point steinerpt);
+  int suppresssteinerpoints();
+
+  void recoverboundary(clock_t&);
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Mesh reconstruction                                                       //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  void carveholes();
+
+  // Comment: These three functions are implemented directly in:
+  //   gmsh_wrk/Mesh/meshGRegionBoundaryRecovery.cpp
+  bool reconstructmesh(void *);
+  void outsurfacemesh(const char* mfilename);
+  void outmesh2medit(const char* mfilename);
+
+  void enqueuesubface(memorypool*, face*);
+  void enqueuetetrahedron(triface*);
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Mesh optimization                                                         //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  long lawsonflip3d(flipconstraints *fc);
+  void recoverdelaunay();
+
+  int  gettetrahedron(point, point, point, point, triface *);
+  long improvequalitybyflips();
+
+  int  smoothpoint(point smtpt, arraypool*, int ccw, optparameters *opm);
+  long improvequalitybysmoothing(optparameters *opm);
+
+  int  splitsliver(triface *, REAL, int);
+  long removeslivers(int);
+
+  void optimizemesh();
+
+  void jettisonnodes();
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Constructor & destructor                                                  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+  void initializetetgenmesh()
+  {
+    in  = addin = NULL;
+    b   = NULL;
+    bgm = NULL;
+
+    tetrahedrons = subfaces = subsegs = points = NULL;
+    badtetrahedrons = badsubfacs = badsubsegs = NULL;
+    tet2segpool = tet2subpool = NULL;
+    flippool = NULL;
+
+    dummypoint = NULL;
+    flipstack = NULL;
+    unflipqueue = NULL;
+
+    cavetetlist = cavebdrylist = caveoldtetlist = NULL;
+    cavetetshlist = cavetetseglist = cavetetvertlist = NULL;
+    caveencshlist = caveencseglist = NULL;
+    caveshlist = caveshbdlist = cavesegshlist = NULL;
+
+    subsegstack = subfacstack = subvertstack = NULL;
+    encseglist = encshlist = NULL;
+    idx2facetlist = NULL;
+    facetverticeslist = NULL;
+    segmentendpointslist = NULL;
+
+    highordertable = NULL;
+
+    numpointattrib = numelemattrib = 0;
+    sizeoftensor = 0;
+    pointmtrindex = 0;
+    pointparamindex = 0;
+    pointmarkindex = 0;
+    point2simindex = 0;
+    pointinsradiusindex = 0;
+    elemattribindex = 0;
+    volumeboundindex = 0;
+    shmarkindex = 0;
+    areaboundindex = 0;
+    checksubsegflag = 0;
+    checksubfaceflag = 0;
+    checkconstraints = 0;
+    nonconvex = 0;
+    autofliplinklevel = 1;
+    useinsertradius = 0;
+    samples = 0l;
+    randomseed = 1l;
+    minfaceang = minfacetdihed = PI;
+    tetprism_vol_sum = 0.0;
+    longest = minedgelength = 0.0;
+    xmax = xmin = ymax = ymin = zmax = zmin = 0.0; 
+
+    insegments = 0l;
+    hullsize = 0l;
+    meshedges = meshhulledges = 0l;
+    steinerleft = -1;
+    dupverts = 0l;
+    unuverts = 0l;
+    nonregularcount = 0l;
+    st_segref_count = st_facref_count = st_volref_count = 0l;
+    fillregioncount = cavitycount = cavityexpcount = 0l;
+    flip14count = flip26count = flipn2ncount = 0l;
+    flip23count = flip32count = flip44count = flip41count = 0l;
+    flip22count = flip31count = 0l;
+    totalworkmemory = 0l;
+
+
+  } // tetgenmesh()
+
+  void freememory()
+  {
+    if (bgm != NULL) {
+      delete bgm;
+    }
+
+    if (points != (memorypool *) NULL) {
+      delete points;
+      delete [] dummypoint;
+    }
+    if (tetrahedrons != (memorypool *) NULL) {
+      delete tetrahedrons;
+    }
+    if (subfaces != (memorypool *) NULL) {
+      delete subfaces;
+      delete subsegs;
+    }
+    if (tet2segpool != NULL) {
+      delete tet2segpool;
+      delete tet2subpool;
+    }
+
+    if (badtetrahedrons) {
+      delete badtetrahedrons;
+    }
+    if (badsubfacs) {
+      delete badsubfacs;
+    }
+    if (badsubsegs) {
+      delete badsubsegs;
+    }
+    if (encseglist) {
+      delete encseglist;
+    }
+    if (encshlist) {
+      delete encshlist;
+    }
+
+    if (flippool != NULL) {
+      delete flippool;
+      delete unflipqueue;
+    }
+
+    if (cavetetlist != NULL) {
+      delete cavetetlist;
+      delete cavebdrylist;
+      delete caveoldtetlist;
+      delete cavetetvertlist;
+    }
+
+    if (caveshlist != NULL) {
+      delete caveshlist;
+      delete caveshbdlist;
+      delete cavesegshlist;
+      delete cavetetshlist;
+      delete cavetetseglist;
+      delete caveencshlist;
+      delete caveencseglist;
+    }
+
+    if (subsegstack != NULL) {
+      delete subsegstack;
+      delete subfacstack;
+      delete subvertstack;
+    }
+
+    if (idx2facetlist != NULL) {
+      delete [] idx2facetlist;
+      delete [] facetverticeslist;
+    }
+
+    if (segmentendpointslist != NULL) {
+      delete [] segmentendpointslist;
+    }
+
+    if (highordertable != NULL) {
+      delete [] highordertable;
+    }
+
+    initializetetgenmesh();
+  }
+
+  tetgenmesh()
+  {
+    initializetetgenmesh();
+  }
+
+  ~tetgenmesh()
+  {
+    freememory();
+  } // ~tetgenmesh()
+
+};                                               // End of class tetgenmesh.
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// terminatetetgen()    Terminate TetGen with a given exit code.             //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+inline void terminatetetgen(tetgenmesh *m, int x)
+{
+#ifdef TETLIBRARY
+  throw x;
+#else
+  switch (x) {
+  case 1: // Out of memory.
+    printf("Error:  Out of memory.\n"); 
+    break;
+  case 2: // Encounter an internal error.
+    printf("Please report this bug to Hang.Si@wias-berlin.de. Include\n");
+    printf("  the message above, your input data set, and the exact\n");
+    printf("  command line you used to run this program, thank you.\n");
+    break;
+  case 3:
+    printf("A self-intersection was detected. Program stopped.\n");
+    printf("Hint: use -d option to detect all self-intersections.\n"); 
+    break;
+  case 4:
+    printf("A very small input feature size was detected. Program stopped.\n");
+    if (m) {
+      printf("Hint: use -T option to set a smaller tolerance. Current is %g\n",
+             m->b->epsilon);
+    }
+    break;
+  case 5:
+    printf("Two very close input facets were detected. Program stopped.\n");
+    printf("Hint: use -Y option to avoid adding Steiner points in boundary.\n");
+    break;
+  case 10: 
+    printf("An input error was detected. Program stopped.\n"); 
+    break;
+  } // switch (x)
+  exit(x);
+#endif // #ifdef TETLIBRARY
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Primitives for tetrahedra                                                 //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+// encode()  compress a handle into a single pointer.  It relies on the 
+//   assumption that all addresses of tetrahedra are aligned to sixteen-
+//   byte boundaries, so that the last four significant bits are zero.
+
+inline tetgenmesh::tetrahedron tetgenmesh::encode(triface& t) {
+  return (tetrahedron) ((uintptr_t) (t).tet | (uintptr_t) (t).ver);
+}
+
+inline tetgenmesh::tetrahedron tetgenmesh::encode2(tetrahedron* ptr, int ver) {
+  return (tetrahedron) ((uintptr_t) (ptr) | (uintptr_t) (ver));
+}
+
+// decode()  converts a pointer to a handle. The version is extracted from
+//   the four least significant bits of the pointer.
+
+inline void tetgenmesh::decode(tetrahedron ptr, triface& t) {
+  (t).ver = (int) ((uintptr_t) (ptr) & (uintptr_t) 15);
+  (t).tet = (tetrahedron *) ((uintptr_t) (ptr) ^ (uintptr_t) (t).ver);
+}
+
+// bond()  connects two tetrahedra together. (t1,v1) and (t2,v2) must 
+//   refer to the same face and the same edge. 
+
+inline void tetgenmesh::bond(triface& t1, triface& t2) {
+  t1.tet[t1.ver & 3] = encode2(t2.tet, bondtbl[t1.ver][t2.ver]);
+  t2.tet[t2.ver & 3] = encode2(t1.tet, bondtbl[t2.ver][t1.ver]);
+}
+
+
+// dissolve()  a bond (from one side).
+
+inline void tetgenmesh::dissolve(triface& t) {
+  t.tet[t.ver & 3] = NULL;
+}
+
+// enext()  finds the next edge (counterclockwise) in the same face.
+
+inline void tetgenmesh::enext(triface& t1, triface& t2) {
+  t2.tet = t1.tet;
+  t2.ver = enexttbl[t1.ver];
+}
+
+inline void tetgenmesh::enextself(triface& t) {
+  t.ver = enexttbl[t.ver];
+}
+
+// eprev()   finds the next edge (clockwise) in the same face.
+
+inline void tetgenmesh::eprev(triface& t1, triface& t2) {
+  t2.tet = t1.tet;
+  t2.ver = eprevtbl[t1.ver];
+}
+
+inline void tetgenmesh::eprevself(triface& t) {
+  t.ver = eprevtbl[t.ver];
+}
+
+// esym()  finds the reversed edge.  It is in the other face of the
+//   same tetrahedron.
+
+inline void tetgenmesh::esym(triface& t1, triface& t2) {
+  (t2).tet = (t1).tet;
+  (t2).ver = esymtbl[(t1).ver];
+}
+
+inline void tetgenmesh::esymself(triface& t) {
+  (t).ver = esymtbl[(t).ver];
+}
+
+// enextesym()  finds the reversed edge of the next edge. It is in the other
+//   face of the same tetrahedron. It is the combination esym() * enext(). 
+
+inline void tetgenmesh::enextesym(triface& t1, triface& t2) {
+  t2.tet = t1.tet;
+  t2.ver = enextesymtbl[t1.ver];
+}
+
+inline void tetgenmesh::enextesymself(triface& t) {
+  t.ver = enextesymtbl[t.ver];
+}
+
+// eprevesym()  finds the reversed edge of the previous edge.
+
+inline void tetgenmesh::eprevesym(triface& t1, triface& t2) {
+  t2.tet = t1.tet;
+  t2.ver = eprevesymtbl[t1.ver];
+}
+
+inline void tetgenmesh::eprevesymself(triface& t) {
+  t.ver = eprevesymtbl[t.ver];
+}
+
+// eorgoppo()    Finds the opposite face of the origin of the current edge.
+//               Return the opposite edge of the current edge.
+
+inline void tetgenmesh::eorgoppo(triface& t1, triface& t2) {
+  t2.tet = t1.tet;
+  t2.ver = eorgoppotbl[t1.ver];
+}
+
+inline void tetgenmesh::eorgoppoself(triface& t) {
+  t.ver = eorgoppotbl[t.ver];
+}
+
+// edestoppo()    Finds the opposite face of the destination of the current 
+//                edge. Return the opposite edge of the current edge.
+
+inline void tetgenmesh::edestoppo(triface& t1, triface& t2) {
+  t2.tet = t1.tet;
+  t2.ver = edestoppotbl[t1.ver];
+}
+
+inline void tetgenmesh::edestoppoself(triface& t) {
+  t.ver = edestoppotbl[t.ver];
+}
+
+// fsym()  finds the adjacent tetrahedron at the same face and the same edge.
+
+inline void tetgenmesh::fsym(triface& t1, triface& t2) {
+  decode((t1).tet[(t1).ver & 3], t2);
+  t2.ver = fsymtbl[t1.ver][t2.ver];
+}
+
+
+#define fsymself(t) \
+  t1ver = (t).ver; \
+  decode((t).tet[(t).ver & 3], (t));\
+  (t).ver = fsymtbl[t1ver][(t).ver]
+
+// fnext()  finds the next face while rotating about an edge according to
+//   a right-hand rule. The face is in the adjacent tetrahedron.  It is
+//   the combination: fsym() * esym().
+
+inline void tetgenmesh::fnext(triface& t1, triface& t2) {
+  decode(t1.tet[facepivot1[t1.ver]], t2);
+  t2.ver = facepivot2[t1.ver][t2.ver];
+}
+
+
+#define fnextself(t) \
+  t1ver = (t).ver; \
+  decode((t).tet[facepivot1[(t).ver]], (t)); \
+  (t).ver = facepivot2[t1ver][(t).ver]
+
+
+// The following primtives get or set the origin, destination, face apex,
+//   or face opposite of an ordered tetrahedron.
+
+inline tetgenmesh::point tetgenmesh::org(triface& t) {
+  return (point) (t).tet[orgpivot[(t).ver]];
+}
+
+inline tetgenmesh::point tetgenmesh:: dest(triface& t) {
+  return (point) (t).tet[destpivot[(t).ver]];
+}
+
+inline tetgenmesh::point tetgenmesh:: apex(triface& t) {
+  return (point) (t).tet[apexpivot[(t).ver]];
+}
+
+inline tetgenmesh::point tetgenmesh:: oppo(triface& t) {
+  return (point) (t).tet[oppopivot[(t).ver]];
+}
+
+inline void tetgenmesh:: setorg(triface& t, point p) {
+  (t).tet[orgpivot[(t).ver]] = (tetrahedron) (p);
+}
+
+inline void tetgenmesh:: setdest(triface& t, point p) {
+  (t).tet[destpivot[(t).ver]] = (tetrahedron) (p);
+}
+
+inline void tetgenmesh:: setapex(triface& t, point p) {
+  (t).tet[apexpivot[(t).ver]] = (tetrahedron) (p);
+}
+
+inline void tetgenmesh:: setoppo(triface& t, point p) {
+  (t).tet[oppopivot[(t).ver]] = (tetrahedron) (p);
+}
+
+#define setvertices(t, torg, tdest, tapex, toppo) \
+  (t).tet[orgpivot[(t).ver]] = (tetrahedron) (torg);\
+  (t).tet[destpivot[(t).ver]] = (tetrahedron) (tdest); \
+  (t).tet[apexpivot[(t).ver]] = (tetrahedron) (tapex); \
+  (t).tet[oppopivot[(t).ver]] = (tetrahedron) (toppo)
+
+// Check or set a tetrahedron's attributes.
+
+inline REAL tetgenmesh::elemattribute(tetrahedron* ptr, int attnum) {
+  return ((REAL *) (ptr))[elemattribindex + attnum];
+}
+
+inline void tetgenmesh::setelemattribute(tetrahedron* ptr, int attnum, 
+  REAL value) {
+  ((REAL *) (ptr))[elemattribindex + attnum] = value;
+}
+
+// Check or set a tetrahedron's maximum volume bound.
+
+inline REAL tetgenmesh::volumebound(tetrahedron* ptr) {
+  return ((REAL *) (ptr))[volumeboundindex];
+}
+
+inline void tetgenmesh::setvolumebound(tetrahedron* ptr, REAL value) {
+  ((REAL *) (ptr))[volumeboundindex] = value;
+}
+
+// Get or set a tetrahedron's index (only used for output).
+//    These two routines use the reserved slot ptr[10].
+
+inline int tetgenmesh::elemindex(tetrahedron* ptr) {
+  int *iptr = (int *) &(ptr[10]);
+  return iptr[0];
+}
+
+inline void tetgenmesh::setelemindex(tetrahedron* ptr, int value) {
+  int *iptr = (int *) &(ptr[10]);
+  iptr[0] = value;
+}
+
+// Get or set a tetrahedron's marker. 
+//   Set 'value = 0' cleans all the face/edge flags.
+
+inline int tetgenmesh::elemmarker(tetrahedron* ptr) {
+  return ((int *) (ptr))[elemmarkerindex];
+}
+
+inline void tetgenmesh::setelemmarker(tetrahedron* ptr, int value) {
+  ((int *) (ptr))[elemmarkerindex] = value;
+}
+
+// infect(), infected(), uninfect() -- primitives to flag or unflag a
+//   tetrahedron. The last bit of the element marker is flagged (1)
+//   or unflagged (0).
+
+inline void tetgenmesh::infect(triface& t) {
+  ((int *) (t.tet))[elemmarkerindex] |= 1;
+}
+
+inline void tetgenmesh::uninfect(triface& t) {
+  ((int *) (t.tet))[elemmarkerindex] &= ~1;
+}
+
+inline bool tetgenmesh::infected(triface& t) {
+  return (((int *) (t.tet))[elemmarkerindex] & 1) != 0;
+}
+
+// marktest(), marktested(), unmarktest() -- primitives to flag or unflag a
+//   tetrahedron.  Use the second lowerest bit of the element marker.
+
+inline void tetgenmesh::marktest(triface& t) {
+  ((int *) (t.tet))[elemmarkerindex] |= 2;
+}
+
+inline void tetgenmesh::unmarktest(triface& t) {
+  ((int *) (t.tet))[elemmarkerindex] &= ~2;
+}
+    
+inline bool tetgenmesh::marktested(triface& t) {
+  return (((int *) (t.tet))[elemmarkerindex] & 2) != 0;
+}
+
+// markface(), unmarkface(), facemarked() -- primitives to flag or unflag a
+//   face of a tetrahedron.  From the last 3rd to 6th bits are used for
+//   face markers, e.g., the last third bit corresponds to loc = 0. 
+
+inline void tetgenmesh::markface(triface& t) {
+  ((int *) (t.tet))[elemmarkerindex] |= (4 << (t.ver & 3));
+}
+
+inline void tetgenmesh::unmarkface(triface& t) {
+  ((int *) (t.tet))[elemmarkerindex] &= ~(4 << (t.ver & 3));
+}
+
+inline bool tetgenmesh::facemarked(triface& t) {
+  return (((int *) (t.tet))[elemmarkerindex] & (4 << (t.ver & 3))) != 0;
+}
+
+// markedge(), unmarkedge(), edgemarked() -- primitives to flag or unflag an
+//   edge of a tetrahedron.  From the last 7th to 12th bits are used for
+//   edge markers, e.g., the last 7th bit corresponds to the 0th edge, etc. 
+//   Remark: The last 7th bit is marked by 2^6 = 64.
+
+inline void tetgenmesh::markedge(triface& t) {
+  ((int *) (t.tet))[elemmarkerindex] |= (int) (64 << ver2edge[(t).ver]);
+}
+
+inline void tetgenmesh::unmarkedge(triface& t) {
+  ((int *) (t.tet))[elemmarkerindex] &= ~(int) (64 << ver2edge[(t).ver]);
+}
+
+inline bool tetgenmesh::edgemarked(triface& t) {
+  return (((int *) (t.tet))[elemmarkerindex] & 
+           (int) (64 << ver2edge[(t).ver])) != 0;
+}
+
+// marktest2(), unmarktest2(), marktest2ed() -- primitives to flag and unflag
+//   a tetrahedron. The 13th bit (2^12 = 4096) is used for this flag.
+
+inline void tetgenmesh::marktest2(triface& t) {
+  ((int *) (t.tet))[elemmarkerindex] |= (int) (4096);
+}
+
+inline void tetgenmesh::unmarktest2(triface& t) {
+  ((int *) (t.tet))[elemmarkerindex] &= ~(int) (4096);
+}
+
+inline bool tetgenmesh::marktest2ed(triface& t) {
+  return (((int *) (t.tet))[elemmarkerindex] & (int) (4096)) != 0;
+}
+
+// elemcounter(), setelemcounter() -- primitives to read or ser a (small)
+//   integer counter in this tet. It is saved from the 16th bit. On 32 bit
+//   system, the range of the counter is [0, 2^15 = 32768]. 
+
+inline int tetgenmesh::elemcounter(triface& t) {
+  return (((int *) (t.tet))[elemmarkerindex]) >> 16;
+}
+
+inline void tetgenmesh::setelemcounter(triface& t, int value) {
+  int c = ((int *) (t.tet))[elemmarkerindex];
+  // Clear the old counter while keep the other flags.
+  c &= 65535; // sum_{i=0^15} 2^i
+  c |= (value << 16);
+  ((int *) (t.tet))[elemmarkerindex] = c;
+}
+
+inline void tetgenmesh::increaseelemcounter(triface& t) {
+  int c = elemcounter(t);
+  setelemcounter(t, c + 1);
+}
+
+inline void tetgenmesh::decreaseelemcounter(triface& t) {
+  int c = elemcounter(t);
+  setelemcounter(t, c - 1);
+}
+
+// ishulltet()  tests if t is a hull tetrahedron.
+
+inline bool tetgenmesh::ishulltet(triface& t) {
+  return (point) (t).tet[7] == dummypoint;
+}
+
+// isdeadtet()  tests if t is a tetrahedron is dead.
+
+inline bool tetgenmesh::isdeadtet(triface& t) {
+  return ((t.tet == NULL) || (t.tet[4] == NULL));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Primitives for subfaces and subsegments                                   //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+// Each subface contains three pointers to its neighboring subfaces, with
+//   edge versions.  To save memory, both information are kept in a single
+//   pointer. To make this possible, all subfaces are aligned to eight-byte
+//   boundaries, so that the last three bits of each pointer are zeros. An
+//   edge version (in the range 0 to 5) is compressed into the last three
+//   bits of each pointer by 'sencode()'.  'sdecode()' decodes a pointer,
+//   extracting an edge version and a pointer to the beginning of a subface.
+
+inline void tetgenmesh::sdecode(shellface sptr, face& s) {
+  s.shver = (int) ((uintptr_t) (sptr) & (uintptr_t) 7);
+  s.sh = (shellface *) ((uintptr_t) (sptr) ^ (uintptr_t) (s.shver));
+}
+
+inline tetgenmesh::shellface tetgenmesh::sencode(face& s) {
+  return (shellface) ((uintptr_t) s.sh | (uintptr_t) s.shver);
+}
+
+inline tetgenmesh::shellface tetgenmesh::sencode2(shellface *sh, int shver) {
+  return (shellface) ((uintptr_t) sh | (uintptr_t) shver);
+}
+
+// sbond() bonds two subfaces (s1) and (s2) together. s1 and s2 must refer
+//   to the same edge. No requirement is needed on their orientations.
+
+inline void tetgenmesh::sbond(face& s1, face& s2) 
+{
+  s1.sh[s1.shver >> 1] = sencode(s2);
+  s2.sh[s2.shver >> 1] = sencode(s1);
+}
+
+// sbond1() bonds s1 <== s2, i.e., after bonding, s1 is pointing to s2,
+//   but s2 is not pointing to s1.  s1 and s2 must refer to the same edge.
+//   No requirement is needed on their orientations.
+
+inline void tetgenmesh::sbond1(face& s1, face& s2) 
+{
+  s1.sh[s1.shver >> 1] = sencode(s2);
+}
+
+// Dissolve a subface bond (from one side).  Note that the other subface
+//   will still think it's connected to this subface.
+
+inline void tetgenmesh::sdissolve(face& s)
+{
+  s.sh[s.shver >> 1] = NULL;
+}
+
+// spivot() finds the adjacent subface (s2) for a given subface (s1).
+//   s1 and s2 share at the same edge.
+
+inline void tetgenmesh::spivot(face& s1, face& s2) 
+{
+  shellface sptr = s1.sh[s1.shver >> 1];
+  sdecode(sptr, s2);
+}
+
+inline void tetgenmesh::spivotself(face& s) 
+{
+  shellface sptr = s.sh[s.shver >> 1];
+  sdecode(sptr, s);
+}
+
+// These primitives determine or set the origin, destination, or apex
+//   of a subface with respect to the edge version.
+
+inline tetgenmesh::point tetgenmesh::sorg(face& s) 
+{
+  return (point) s.sh[sorgpivot[s.shver]];
+}
+
+inline tetgenmesh::point tetgenmesh::sdest(face& s) 
+{
+  return (point) s.sh[sdestpivot[s.shver]];
+}
+
+inline tetgenmesh::point tetgenmesh::sapex(face& s) 
+{
+  return (point) s.sh[sapexpivot[s.shver]];
+}
+
+inline void tetgenmesh::setsorg(face& s, point pointptr) 
+{
+  s.sh[sorgpivot[s.shver]] = (shellface) pointptr;
+}
+
+inline void tetgenmesh::setsdest(face& s, point pointptr) 
+{
+  s.sh[sdestpivot[s.shver]] = (shellface) pointptr;
+}
+
+inline void tetgenmesh::setsapex(face& s, point pointptr) 
+{
+  s.sh[sapexpivot[s.shver]] = (shellface) pointptr;
+}
+
+#define setshvertices(s, pa, pb, pc)\
+  setsorg(s, pa);\
+  setsdest(s, pb);\
+  setsapex(s, pc)
+
+// sesym()  reserves the direction of the lead edge.
+
+inline void tetgenmesh::sesym(face& s1, face& s2) 
+{
+  s2.sh = s1.sh;
+  s2.shver = (s1.shver ^ 1);  // Inverse the last bit.
+}
+
+inline void tetgenmesh::sesymself(face& s) 
+{
+  s.shver ^= 1;
+}
+
+// senext()  finds the next edge (counterclockwise) in the same orientation
+//   of this face.
+
+inline void tetgenmesh::senext(face& s1, face& s2) 
+{
+  s2.sh = s1.sh;
+  s2.shver = snextpivot[s1.shver];
+}
+
+inline void tetgenmesh::senextself(face& s) 
+{
+  s.shver = snextpivot[s.shver];
+}
+
+inline void tetgenmesh::senext2(face& s1, face& s2) 
+{
+  s2.sh = s1.sh;
+  s2.shver = snextpivot[snextpivot[s1.shver]];
+}
+
+inline void tetgenmesh::senext2self(face& s) 
+{
+  s.shver = snextpivot[snextpivot[s.shver]];
+}
+
+
+// Check or set a subface's maximum area bound.
+
+inline REAL tetgenmesh::areabound(face& s) 
+{
+  return ((REAL *) (s.sh))[areaboundindex];
+}
+
+inline void tetgenmesh::setareabound(face& s, REAL value) 
+{
+  ((REAL *) (s.sh))[areaboundindex] = value;
+}
+
+// These two primitives read or set a shell marker.  Shell markers are used
+//   to hold user boundary information.
+
+inline int tetgenmesh::shellmark(face& s) 
+{
+  return ((int *) (s.sh))[shmarkindex];
+}
+
+inline void tetgenmesh::setshellmark(face& s, int value) 
+{
+  ((int *) (s.sh))[shmarkindex] = value;
+}
+
+
+
+// sinfect(), sinfected(), suninfect() -- primitives to flag or unflag a
+//   subface. The last bit of ((int *) ((s).sh))[shmarkindex+1] is flagged.
+
+inline void tetgenmesh::sinfect(face& s) 
+{
+  ((int *) ((s).sh))[shmarkindex+1] = 
+    (((int *) ((s).sh))[shmarkindex+1] | (int) 1);
+}
+
+inline void tetgenmesh::suninfect(face& s) 
+{
+  ((int *) ((s).sh))[shmarkindex+1] = 
+    (((int *) ((s).sh))[shmarkindex+1] & ~(int) 1);
+}
+
+// Test a subface for viral infection.
+
+inline bool tetgenmesh::sinfected(face& s) 
+{
+  return (((int *) ((s).sh))[shmarkindex+1] & (int) 1) != 0;
+}
+
+// smarktest(), smarktested(), sunmarktest() -- primitives to flag or unflag
+//   a subface. The last 2nd bit of the integer is flagged.
+
+inline void tetgenmesh::smarktest(face& s) 
+{
+  ((int *) ((s).sh))[shmarkindex+1] = 
+    (((int *)((s).sh))[shmarkindex+1] | (int) 2);
+}
+
+inline void tetgenmesh::sunmarktest(face& s) 
+{
+  ((int *) ((s).sh))[shmarkindex+1] = 
+    (((int *)((s).sh))[shmarkindex+1] & ~(int)2);
+}
+
+inline bool tetgenmesh::smarktested(face& s) 
+{
+  return ((((int *) ((s).sh))[shmarkindex+1] & (int) 2) != 0);
+}
+
+// smarktest2(), smarktest2ed(), sunmarktest2() -- primitives to flag or 
+//   unflag a subface. The last 3rd bit of the integer is flagged.
+
+inline void tetgenmesh::smarktest2(face& s) 
+{
+  ((int *) ((s).sh))[shmarkindex+1] = 
+    (((int *)((s).sh))[shmarkindex+1] | (int) 4);
+}
+
+inline void tetgenmesh::sunmarktest2(face& s) 
+{
+  ((int *) ((s).sh))[shmarkindex+1] = 
+    (((int *)((s).sh))[shmarkindex+1] & ~(int)4);
+}
+
+inline bool tetgenmesh::smarktest2ed(face& s) 
+{
+  return ((((int *) ((s).sh))[shmarkindex+1] & (int) 4) != 0);
+}
+
+// The last 4th bit of ((int *) ((s).sh))[shmarkindex+1] is flagged.
+
+inline void tetgenmesh::smarktest3(face& s) 
+{
+  ((int *) ((s).sh))[shmarkindex+1] = 
+    (((int *)((s).sh))[shmarkindex+1] | (int) 8);
+}
+
+inline void tetgenmesh::sunmarktest3(face& s) 
+{
+  ((int *) ((s).sh))[shmarkindex+1] = 
+    (((int *)((s).sh))[shmarkindex+1] & ~(int)8);
+}
+
+inline bool tetgenmesh::smarktest3ed(face& s) 
+{
+  return ((((int *) ((s).sh))[shmarkindex+1] & (int) 8) != 0);
+}
+
+
+// Each facet has a unique index (automatically indexed). Starting from '0'.
+// We save this index in the same field of the shell type. 
+
+inline void tetgenmesh::setfacetindex(face& s, int value)
+{
+  ((int *) (s.sh))[shmarkindex + 2] = value;
+}
+
+inline int tetgenmesh::getfacetindex(face& s)
+{
+  return ((int *) (s.sh))[shmarkindex + 2];
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Primitives for interacting between tetrahedra and subfaces                //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+// tsbond() bond a tetrahedron (t) and a subface (s) together.
+// Note that t and s must be the same face and the same edge. Moreover,
+//   t and s have the same orientation. 
+// Since the edge number in t and in s can be any number in {0,1,2}. We bond
+//   the edge in s which corresponds to t's 0th edge, and vice versa.
+
+inline void tetgenmesh::tsbond(triface& t, face& s)
+{
+  if ((t).tet[9] == NULL) {
+    // Allocate space for this tet.
+    (t).tet[9] = (tetrahedron) tet2subpool->alloc();
+    // Initialize.
+    for (int i = 0; i < 4; i++) {
+      ((shellface *) (t).tet[9])[i] = NULL;
+    }
+  }
+  // Bond t <== s.
+  ((shellface *) (t).tet[9])[(t).ver & 3] = 
+    sencode2((s).sh, tsbondtbl[t.ver][s.shver]);
+  // Bond s <== t.
+  s.sh[9 + ((s).shver & 1)] = 
+    (shellface) encode2((t).tet, stbondtbl[t.ver][s.shver]);
+}
+
+// tspivot() finds a subface (s) abutting on the given tetrahdera (t).
+//   Return s.sh = NULL if there is no subface at t. Otherwise, return
+//   the subface s, and s and t must be at the same edge wth the same
+//   orientation.
+
+inline void tetgenmesh::tspivot(triface& t, face& s) 
+{
+  if ((t).tet[9] == NULL) {
+    (s).sh = NULL;
+    return;
+  }
+  // Get the attached subface s.
+  sdecode(((shellface *) (t).tet[9])[(t).ver & 3], (s));
+  (s).shver = tspivottbl[t.ver][s.shver];
+}
+
+// Quickly check if the handle (t, v) is a subface.
+#define issubface(t) \
+  ((t).tet[9] && ((t).tet[9])[(t).ver & 3])
+
+// stpivot() finds a tetrahedron (t) abutting a given subface (s).
+//   Return the t (if it exists) with the same edge and the same
+//   orientation of s.
+
+inline void tetgenmesh::stpivot(face& s, triface& t) 
+{
+  decode((tetrahedron) s.sh[9 + (s.shver & 1)], t);
+  if ((t).tet == NULL) {
+    return;
+  }
+  (t).ver = stpivottbl[t.ver][s.shver];
+}
+
+// Quickly check if this subface is attached to a tetrahedron.
+
+#define isshtet(s) \
+  ((s).sh[9 + ((s).shver & 1)])
+
+// tsdissolve() dissolve a bond (from the tetrahedron side).
+
+inline void tetgenmesh::tsdissolve(triface& t) 
+{
+  if ((t).tet[9] != NULL) {
+    ((shellface *) (t).tet[9])[(t).ver & 3] = NULL;
+  }
+}
+
+// stdissolve() dissolve a bond (from the subface side).
+
+inline void tetgenmesh::stdissolve(face& s) 
+{
+  (s).sh[9] = NULL;
+  (s).sh[10] = NULL;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Primitives for interacting between subfaces and segments                  //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+// ssbond() bond a subface to a subsegment.
+
+inline void tetgenmesh::ssbond(face& s, face& edge) 
+{
+  s.sh[6 + (s.shver >> 1)] = sencode(edge);
+  edge.sh[0] = sencode(s);
+}
+
+inline void tetgenmesh::ssbond1(face& s, face& edge) 
+{
+  s.sh[6 + (s.shver >> 1)] = sencode(edge);
+  //edge.sh[0] = sencode(s);
+}
+
+// ssdisolve() dissolve a bond (from the subface side)
+
+inline void tetgenmesh::ssdissolve(face& s) 
+{
+  s.sh[6 + (s.shver >> 1)] = NULL;
+}
+
+// sspivot() finds a subsegment abutting a subface.
+
+inline void tetgenmesh::sspivot(face& s, face& edge) 
+{
+  sdecode((shellface) s.sh[6 + (s.shver >> 1)], edge);
+}
+
+// Quickly check if the edge is a subsegment.
+
+#define isshsubseg(s) \
+  ((s).sh[6 + ((s).shver >> 1)])
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Primitives for interacting between tetrahedra and segments                //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+inline void tetgenmesh::tssbond1(triface& t, face& s)
+{
+  if ((t).tet[8] == NULL) {
+    // Allocate space for this tet.
+    (t).tet[8] = (tetrahedron) tet2segpool->alloc();
+    // Initialization.
+    for (int i = 0; i < 6; i++) {
+      ((shellface *) (t).tet[8])[i] = NULL;
+    }
+  }
+  ((shellface *) (t).tet[8])[ver2edge[(t).ver]] = sencode((s)); 
+}
+
+inline void tetgenmesh::sstbond1(face& s, triface& t) 
+{
+  ((tetrahedron *) (s).sh)[9] = encode(t);
+}
+
+inline void tetgenmesh::tssdissolve1(triface& t)
+{
+  if ((t).tet[8] != NULL) {
+    ((shellface *) (t).tet[8])[ver2edge[(t).ver]] = NULL;
+  }
+}
+
+inline void tetgenmesh::sstdissolve1(face& s) 
+{
+  ((tetrahedron *) (s).sh)[9] = NULL;
+}
+
+inline void tetgenmesh::tsspivot1(triface& t, face& s)
+{
+  if ((t).tet[8] != NULL) {
+    sdecode(((shellface *) (t).tet[8])[ver2edge[(t).ver]], s);
+  } else {
+    (s).sh = NULL;
+  }
+}
+
+// Quickly check whether 't' is a segment or not.
+
+#define issubseg(t) \
+  ((t).tet[8] && ((t).tet[8])[ver2edge[(t).ver]])
+
+inline void tetgenmesh::sstpivot1(face& s, triface& t) 
+{
+  decode((tetrahedron) s.sh[9], t);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Primitives for points                                                     //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+inline int tetgenmesh::pointmark(point pt) { 
+  return ((int *) (pt))[pointmarkindex]; 
+}
+
+inline void tetgenmesh::setpointmark(point pt, int value) {
+  ((int *) (pt))[pointmarkindex] = value;
+}
+
+
+// These two primitives set and read the type of the point.
+
+inline enum tetgenmesh::verttype tetgenmesh::pointtype(point pt) {
+  return (enum verttype) (((int *) (pt))[pointmarkindex + 1] >> (int) 8);
+}
+
+inline void tetgenmesh::setpointtype(point pt, enum verttype value) {
+  ((int *) (pt))[pointmarkindex + 1] = 
+    ((int) value << 8) + (((int *) (pt))[pointmarkindex + 1] & (int) 255);
+}
+
+// Read and set the geometry tag of the point (used by -s option).
+
+inline int tetgenmesh::pointgeomtag(point pt) { 
+  return ((int *) (pt))[pointmarkindex + 2]; 
+}
+
+inline void tetgenmesh::setpointgeomtag(point pt, int value) {
+  ((int *) (pt))[pointmarkindex + 2] = value;
+}
+
+// Read and set the u,v coordinates of the point (used by -s option).
+
+inline REAL tetgenmesh::pointgeomuv(point pt, int i) {
+  return pt[pointparamindex + i];
+}
+
+inline void tetgenmesh::setpointgeomuv(point pt, int i, REAL value) {
+  pt[pointparamindex + i] = value;
+}
+
+// pinfect(), puninfect(), pinfected() -- primitives to flag or unflag
+//   a point. The last bit of the integer '[pointindex+1]' is flagged.
+
+inline void tetgenmesh::pinfect(point pt) {
+  ((int *) (pt))[pointmarkindex + 1] |= (int) 1;
+}
+
+inline void tetgenmesh::puninfect(point pt) {
+  ((int *) (pt))[pointmarkindex + 1] &= ~(int) 1;
+}
+
+inline bool tetgenmesh::pinfected(point pt) {
+  return (((int *) (pt))[pointmarkindex + 1] & (int) 1) != 0;
+}
+
+// pmarktest(), punmarktest(), pmarktested() -- more primitives to 
+//   flag or unflag a point. 
+
+inline void tetgenmesh::pmarktest(point pt) {
+  ((int *) (pt))[pointmarkindex + 1] |= (int) 2;
+}
+
+inline void tetgenmesh::punmarktest(point pt) {
+  ((int *) (pt))[pointmarkindex + 1] &= ~(int) 2;
+}
+
+inline bool tetgenmesh::pmarktested(point pt) {
+  return (((int *) (pt))[pointmarkindex + 1] & (int) 2) != 0;
+}
+
+inline void tetgenmesh::pmarktest2(point pt) {
+  ((int *) (pt))[pointmarkindex + 1] |= (int) 4;
+}
+
+inline void tetgenmesh::punmarktest2(point pt) {
+  ((int *) (pt))[pointmarkindex + 1] &= ~(int) 4;
+}
+
+inline bool tetgenmesh::pmarktest2ed(point pt) {
+  return (((int *) (pt))[pointmarkindex + 1] & (int) 4) != 0;
+}
+
+inline void tetgenmesh::pmarktest3(point pt) {
+  ((int *) (pt))[pointmarkindex + 1] |= (int) 8;
+}
+
+inline void tetgenmesh::punmarktest3(point pt) {
+  ((int *) (pt))[pointmarkindex + 1] &= ~(int) 8;
+}
+
+inline bool tetgenmesh::pmarktest3ed(point pt) {
+  return (((int *) (pt))[pointmarkindex + 1] & (int) 8) != 0;
+}
+
+// These following primitives set and read a pointer to a tetrahedron
+//   a subface/subsegment, a point, or a tet of background mesh.
+
+inline tetgenmesh::tetrahedron tetgenmesh::point2tet(point pt) {
+  return ((tetrahedron *) (pt))[point2simindex];
+}
+
+inline void tetgenmesh::setpoint2tet(point pt, tetrahedron value) {
+  ((tetrahedron *) (pt))[point2simindex] = value;
+}
+
+inline tetgenmesh::point tetgenmesh::point2ppt(point pt) {
+  return (point) ((tetrahedron *) (pt))[point2simindex + 1];
+}
+
+inline void tetgenmesh::setpoint2ppt(point pt, point value) {
+  ((tetrahedron *) (pt))[point2simindex + 1] = (tetrahedron) value;
+}
+
+inline tetgenmesh::shellface tetgenmesh::point2sh(point pt) {
+  return (shellface) ((tetrahedron *) (pt))[point2simindex + 2];
+}
+
+inline void tetgenmesh::setpoint2sh(point pt, shellface value) {
+  ((tetrahedron *) (pt))[point2simindex + 2] = (tetrahedron) value;
+}
+
+
+inline tetgenmesh::tetrahedron tetgenmesh::point2bgmtet(point pt) {
+  return ((tetrahedron *) (pt))[point2simindex + 3];
+}
+
+inline void tetgenmesh::setpoint2bgmtet(point pt, tetrahedron value) {
+  ((tetrahedron *) (pt))[point2simindex + 3] = value;
+}
+
+
+// The primitives for saving and getting the insertion radius.
+inline void tetgenmesh::setpointinsradius(point pt, REAL value)
+{
+  pt[pointinsradiusindex] = value;
+}
+
+inline REAL tetgenmesh::getpointinsradius(point pt)
+{
+  return pt[pointinsradiusindex];
+}
+
+inline bool tetgenmesh::issteinerpoint(point pt) {
+ return (pointtype(pt) == FREESEGVERTEX) || (pointtype(pt) == FREEFACETVERTEX)
+        || (pointtype(pt) == FREEVOLVERTEX);
+}
+
+// point2tetorg()    Get the tetrahedron whose origin is the point.
+
+inline void tetgenmesh::point2tetorg(point pa, triface& searchtet)
+{
+  decode(point2tet(pa), searchtet);
+  if ((point) searchtet.tet[4] == pa) {
+    searchtet.ver = 11;
+  } else if ((point) searchtet.tet[5] == pa) {
+    searchtet.ver = 3;
+  } else if ((point) searchtet.tet[6] == pa) {
+    searchtet.ver = 7;
+  } else {
+    searchtet.ver = 0;
+  }
+}
+
+// point2shorg()    Get the subface/segment whose origin is the point.
+
+inline void tetgenmesh::point2shorg(point pa, face& searchsh)
+{
+  sdecode(point2sh(pa), searchsh);
+  if ((point) searchsh.sh[3] == pa) {
+    searchsh.shver = 0;
+  } else if ((point) searchsh.sh[4] == pa) {
+    searchsh.shver = (searchsh.sh[5] != NULL ? 2 : 1); 
+  } else {
+    searchsh.shver = 4;
+  }
+}
+
+// farsorg()    Return the origin of the subsegment.
+// farsdest()   Return the destination of the subsegment.
+
+inline tetgenmesh::point tetgenmesh::farsorg(face& s)
+{
+  face travesh, neighsh;
+
+  travesh = s;
+  while (1) {
+    senext2(travesh, neighsh);
+    spivotself(neighsh); 
+    if (neighsh.sh == NULL) break;
+    if (sorg(neighsh) != sorg(travesh)) sesymself(neighsh);
+    senext2(neighsh, travesh); 
+  }
+  return sorg(travesh);
+}
+
+inline tetgenmesh::point tetgenmesh::farsdest(face& s) 
+{
+  face travesh, neighsh;
+
+  travesh = s;
+  while (1) {
+    senext(travesh, neighsh);
+    spivotself(neighsh); 
+    if (neighsh.sh == NULL) break;
+    if (sdest(neighsh) != sdest(travesh)) sesymself(neighsh);
+    senext(neighsh, travesh); 
+  }
+  return sdest(travesh);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                                                                           //
+// Linear algebra operators.                                                 //
+//                                                                           //
+///////////////////////////////////////////////////////////////////////////////
+
+// dot() returns the dot product: v1 dot v2.
+inline REAL tetgenmesh::dot(REAL* v1, REAL* v2) 
+{
+  return v1[0] * v2[0] + v1[1] * v2[1] + v1[2] * v2[2];
+}
+
+// cross() computes the cross product: n = v1 cross v2.
+inline void tetgenmesh::cross(REAL* v1, REAL* v2, REAL* n) 
+{
+  n[0] =   v1[1] * v2[2] - v2[1] * v1[2];
+  n[1] = -(v1[0] * v2[2] - v2[0] * v1[2]);
+  n[2] =   v1[0] * v2[1] - v2[0] * v1[1];
+}
+
+// distance() computes the Euclidean distance between two points.
+inline REAL tetgenmesh::distance(REAL* p1, REAL* p2)
+{
+  return sqrt((p2[0] - p1[0]) * (p2[0] - p1[0]) +
+              (p2[1] - p1[1]) * (p2[1] - p1[1]) +
+              (p2[2] - p1[2]) * (p2[2] - p1[2]));
+}
+
+inline REAL tetgenmesh::norm2(REAL x, REAL y, REAL z)
+{
+  return (x) * (x) + (y) * (y) + (z) * (z);
+}
+
+#endif // tetgenBRH