relocate nodes example

doc/texinfo/api.texi

@@ -1588,6 +1588,8 @@ negative, relocate all the nodes in the mesh.
 -
 @item Language-specific definition:
 @url{@value{GITLAB-PREFIX}/api/gmsh.h#L857,C++}, @url{@value{GITLAB-PREFIX}/api/gmshc.h#L738,C}, @url{@value{GITLAB-PREFIX}/api/gmsh.py#L2570,Python}, @url{@value{GITLAB-PREFIX}/api/gmsh.jl#L2217,Julia}
+@item Examples:
+Python (@url{@value{GITLAB-PREFIX}/examples/api/relocate_nodes.py#L48,relocate_nodes.py})
 @end table
 
 @item gmsh/model/mesh/getElements
@@ -4233,7 +4235,7 @@ integer
 @item Language-specific definition:
 @url{@value{GITLAB-PREFIX}/api/gmsh.h#L2433,C++}, @url{@value{GITLAB-PREFIX}/api/gmshc.h#L2137,C}, @url{@value{GITLAB-PREFIX}/api/gmsh.py#L6644,Python}, @url{@value{GITLAB-PREFIX}/api/gmsh.jl#L5918,Julia}
 @item Examples:
-Python (@url{@value{GITLAB-PREFIX}/examples/api/crack.py#L13,crack.py}, @url{@value{GITLAB-PREFIX}/examples/api/naca_boundary_layer_2d.py#L67,naca_boundary_layer_2d.py}, @url{@value{GITLAB-PREFIX}/examples/api/naca_boundary_layer_3d.py#L70,naca_boundary_layer_3d.py}, @url{@value{GITLAB-PREFIX}/examples/api/stl_to_brep.py#L41,stl_to_brep.py})
+Python (@url{@value{GITLAB-PREFIX}/examples/api/crack.py#L13,crack.py}, @url{@value{GITLAB-PREFIX}/examples/api/naca_boundary_layer_2d.py#L67,naca_boundary_layer_2d.py}, @url{@value{GITLAB-PREFIX}/examples/api/naca_boundary_layer_3d.py#L70,naca_boundary_layer_3d.py}, @url{@value{GITLAB-PREFIX}/examples/api/relocate_nodes.py#L10,relocate_nodes.py}, @url{@value{GITLAB-PREFIX}/examples/api/stl_to_brep.py#L41,stl_to_brep.py})
 @end table
 
 @item gmsh/model/occ/addCircleArc
@@ -4422,7 +4424,7 @@ integer
 @item Language-specific definition:
 @url{@value{GITLAB-PREFIX}/api/gmsh.h#L2562,C++}, @url{@value{GITLAB-PREFIX}/api/gmshc.h#L2257,C}, @url{@value{GITLAB-PREFIX}/api/gmsh.py#L6960,Python}, @url{@value{GITLAB-PREFIX}/api/gmsh.jl#L6180,Julia}
 @item Examples:
-C++ (@url{@value{GITLAB-PREFIX}/tutorials/c++/t19.cpp#L26,t19.cpp}), Python (@url{@value{GITLAB-PREFIX}/tutorials/python/t19.py#L24,t19.py}, @url{@value{GITLAB-PREFIX}/examples/api/naca_boundary_layer_2d.py#L73,naca_boundary_layer_2d.py}, @url{@value{GITLAB-PREFIX}/examples/api/stl_to_brep.py#L46,stl_to_brep.py}, @url{@value{GITLAB-PREFIX}/examples/api/surface_filling.py#L16,surface_filling.py})
+C++ (@url{@value{GITLAB-PREFIX}/tutorials/c++/t19.cpp#L26,t19.cpp}), Python (@url{@value{GITLAB-PREFIX}/tutorials/python/t19.py#L24,t19.py}, @url{@value{GITLAB-PREFIX}/examples/api/naca_boundary_layer_2d.py#L73,naca_boundary_layer_2d.py}, @url{@value{GITLAB-PREFIX}/examples/api/relocate_nodes.py#L15,relocate_nodes.py}, @url{@value{GITLAB-PREFIX}/examples/api/stl_to_brep.py#L46,stl_to_brep.py}, @url{@value{GITLAB-PREFIX}/examples/api/surface_filling.py#L16,surface_filling.py})
 @end table
 
 @item gmsh/model/occ/addRectangle
@@ -4517,7 +4519,7 @@ integer
 @item Language-specific definition:
 @url{@value{GITLAB-PREFIX}/api/gmsh.h#L2629,C++}, @url{@value{GITLAB-PREFIX}/api/gmshc.h#L2319,C}, @url{@value{GITLAB-PREFIX}/api/gmsh.py#L7100,Python}, @url{@value{GITLAB-PREFIX}/api/gmsh.jl#L6315,Julia}
 @item Examples:
-Python (@url{@value{GITLAB-PREFIX}/examples/api/surface_filling.py#L19,surface_filling.py})
+Python (@url{@value{GITLAB-PREFIX}/examples/api/relocate_nodes.py#L21,relocate_nodes.py}, @url{@value{GITLAB-PREFIX}/examples/api/surface_filling.py#L19,surface_filling.py})
 @end table
 
 @item gmsh/model/occ/addBSplineFilling

examples/api/relocate_nodes.py

+import gmsh
+import sys
+
+def add_house(A, B, C):
+    p1 = gmsh.model.occ.addPoint(0, 0, 0)
+    p2 = gmsh.model.occ.addPoint(A, 0, 0)
+    p3 = gmsh.model.occ.addPoint(A, B, 0)
+    p4 = gmsh.model.occ.addPoint(A/2, B+C, 0)
+    p5 = gmsh.model.occ.addPoint(0, B, 0)
+    l1 = gmsh.model.occ.addLine(p1, p2)
+    l2 = gmsh.model.occ.addLine(p2, p3)
+    l3 = gmsh.model.occ.addLine(p3, p4)
+    l4 = gmsh.model.occ.addLine(p4, p5)
+    l5 = gmsh.model.occ.addLine(p5, p1)
+    cl = gmsh.model.occ.addCurveLoop([l1, l2, l3, l4, l5])
+
+    # plane surface - inner nodes will not move as parametrization is R2
+    # s = gmsh.model.occ.addPlaneFilling([cl])
+
+    # BSpline surface - inner nodes will move
+    s = gmsh.model.occ.addSurfaceFilling(cl)
+    gmsh.model.occ.synchronize()
+
+gmsh.initialize(sys.argv)
+
+# create initial geometry
+gmsh.model.add('house1')
+add_house(10, 8, 5)
+
+# mesh it and store the mesh
+gmsh.model.mesh.generate(2)
+m = {}
+for e in gmsh.model.getEntities():
+    m[e] = (gmsh.model.mesh.getNodes(e[0], e[1]),
+            gmsh.model.mesh.getElements(e[0], e[1]))
+
+# create perturbed geometry
+gmsh.model.add('house2')
+add_house(9.5, 8.2, 5.1)
+
+# copy old mesh into perturbed geometry
+for e in m:
+    gmsh.model.mesh.addNodes(e[0], e[1], m[e][0][0], m[e][0][1], m[e][0][2])
+    gmsh.model.mesh.addElements(e[0], e[1], m[e][1][0], m[e][1][1], m[e][1][2])
+
+# relocate mesh nodes on the perturbed geometry, using the parametric
+# coordinates from the initial geometry
+gmsh.model.mesh.relocateNodes()
+
+if '-nopopup' not in sys.argv:
+    gmsh.fltk.run()
+
+gmsh.finalize()