fix orientation of surface mesh for OCC models

Mesh/meshGFace.cpp

@@ -1418,15 +1418,35 @@ void orientMeshGFace::operator()(GFace *gf)
 
   if(gf->geomType() == GEntity::ProjectionFace) return;
 
-  // surface orientions in OCC are not consistent with the orientation
-  // of the bounding edges, so just leave them unchanged:
-  if(gf->getNativeType() == GEntity::OpenCascadeModel) return;
-
   // in old versions we did not reorient transfinite surface meshes;
   // we could add the following to provide backward compatibility:
   // if(gf->meshAttributes.Method == MESH_TRANSFINITE) return;
 
-  // orients the mesh to match the orientation of the first edge
+  if(gf->getNativeType() == GEntity::OpenCascadeModel){
+    // surface orientions in OCC do not seem to be consistent with the
+    // orientation of the bounding edges, so we compare the normals
+    // pointwise in an element
+    for(int i = 0; i < gf->getNumMeshElements(); i++){
+      MElement *e = gf->getMeshElement(i);
+      for(int j = 0; j < e->getNumVertices(); j++){
+        MVertex *v = e->getVertex(j);
+        SPoint2 param;
+        if(reparamMeshVertexOnFace(v, gf, param)){
+          SVector3 ne = e->getFace(0).normal();
+          SVector3 nf = gf->normal(param); 
+          if(dot(ne, nf) < 0){
+            Msg::Debug("Reverting orientation of mesh in face %d", gf->tag());
+            for(int k = 0; k < gf->getNumMeshElements(); k++)
+              gf->getMeshElement(k)->revert();
+          }
+          return;
+        }
+      }
+    }
+    Msg::Warning("Could not orient mesh in face %d", gf->tag());
+  }
+  else{
+    // orient the mesh to match the orientation of the first edge
     std::list<GEdge*> edges = gf->edges();
     std::list<int> ori = gf->orientations();
     if(edges.empty() || ori.empty()) return;
@@ -1446,3 +1466,4 @@ void orientMeshGFace::operator()(GFace *gf)
         gf->quadrangles[i]->revert();
     }
   }
+}

doc/VERSIONS.txt

-$Id: VERSIONS.txt,v 1.38 2009-03-13 08:04:38 geuzaine Exp $
+$Id: VERSIONS.txt,v 1.39 2009-03-15 10:36:40 geuzaine Exp $
 
 (?): removed GSL dependency (Gmsh now simply requires Blas and
 Lapack); new per-window visibility; added support for composite window
-printing and background images; fixes for string options in parser.
+printing and background images; fixes for string options in parser;
+fixed surface mesh orientation for Open Cascade models.
 
 2.3.0 (Jan 23, 2009): major graphics and GUI code refactoring; new
 full-quad/hexa subdivision algorithm (removed Mesh.RecombineAlgo);