--- /dev/null
+/*!
+
+\page tui_use_existing_faces Use existing faces
+
+This sample demonstrates how to use <b>Use existing faces</b> algorithm,
+which is actulally just a stub allowing to use your own 2D algoritm
+implemented in Python.
+
+
+\code
+import smesh, geompy
+import numpy as np
+
+# define my 2D algorithm
+def my2DMeshing( geomFace ):
+
+ # find gravity center of geomFace
+ gcXYZ = geompy.PointCoordinates( geompy.MakeCDG( geomFace ))
+
+ # define order and orientation of edges
+ sortedEdges = []
+ geomEdges = geompy.SubShapeAll( geomFace, geompy.ShapeType["EDGE"])
+ sortedEdges.append(( geomEdges.pop(0), True ))
+ while geomEdges:
+ prevEdge_rev = sortedEdges[ -1 ]
+ prevVV = geompy.SubShapeAll( prevEdge_rev[0], geompy.ShapeType["VERTEX"])
+ prevV2 = prevVV[ prevEdge_rev[1] ]
+ found = False
+ for iE in range( len( geomEdges )):
+ v1,v2 = geompy.SubShapeAll( geomEdges[ iE ], geompy.ShapeType["VERTEX"])
+ same1,same2 = [( geompy.MinDistance( prevV2, v ) < 1e-7 ) for v in [v1,v2] ]
+ if not same1 and not same2: continue
+ sortedEdges.append(( geomEdges.pop( iE ), same1 ))
+ found = True
+ break
+ assert found
+ sortedEdges.reverse()
+
+ # put nodes on edges in a right order
+ nodes = []
+ for edge, isForward in sortedEdges:
+ v1,v2 = geompy.SubShapeAll( edge, geompy.ShapeType["VERTEX"])
+ edgeNodes = mesh.GetSubMeshNodesId( v2, all=False ) + \
+ mesh.GetSubMeshNodesId( edge, all=False ) + \
+ mesh.GetSubMeshNodesId( v1, all=False )
+ if not isForward: edgeNodes.reverse()
+ nodes.extend( edgeNodes[:-1] )
+
+ # create nodes inside the geomFace
+ r1 = 0.6
+ r2 = 1 - r1
+ nodesInside = []
+ for n in nodes:
+ nXYZ = mesh.GetNodeXYZ( n )
+ newXYZ = np.add( np.multiply( r1, gcXYZ ), np.multiply( r2, nXYZ ))
+ nodesInside.append( mesh.AddNode( newXYZ[0], newXYZ[1], newXYZ[2] ))
+ mesh.SetNodeOnFace( nodesInside[-1], geomFace, 0, 0 )
+
+ # find out orientation of faces to create
+ # geomFace normal
+ faceNorm = geompy.GetNormal( geomFace )
+ v1,v2 = [ geompy.PointCoordinates( v ) \
+ for v in geompy.SubShapeAll( faceNorm, geompy.ShapeType["VERTEX"]) ]
+ faceNormXYZ = np.subtract( v2, v1 )
+ outDirXYZ = np.subtract( v1, [ 50, 50, 50 ] )
+ if np.dot( faceNormXYZ, outDirXYZ ) < 0: # reversed face
+ faceNormXYZ = np.multiply( -1., faceNormXYZ )
+ # mesh face normal
+ e1 = np.subtract( mesh.GetNodeXYZ( nodes[0] ), mesh.GetNodeXYZ( nodes[1] ))
+ e2 = np.subtract( mesh.GetNodeXYZ( nodes[0] ), mesh.GetNodeXYZ( nodesInside[0] ))
+ meshNorm = np.cross( e1, e2 )
+ # faces orientation
+ reverse = ( np.dot( faceNormXYZ, meshNorm ) < 0 )
+
+ # create mesh faces
+ iN = len( nodes )
+ while iN:
+ n1, n2, n3, n4 = nodes[iN-1], nodes[iN-2], nodesInside[iN-2], nodesInside[iN-1]
+ iN -= 1
+ if reverse:
+ f = mesh.AddFace( [n1, n2, n3, n4] )
+ else:
+ f = mesh.AddFace( [n4, n3, n2, n1] )
+ # new faces must be assigned to geometry to allow 3D algorithm finding them
+ mesh.SetMeshElementOnShape( f, geomFace )
+
+ if reverse:
+ nodesInside.reverse()
+ polygon = mesh.AddPolygonalFace( nodesInside )
+ mesh.SetMeshElementOnShape( polygon, geomFace )
+
+ return
+
+# create geometry and get faces to mesh with my2DMeshing()
+box = geompy.MakeBoxDXDYDZ( 100, 100, 100 )
+f1 = geompy.SubShapeAll( box, geompy.ShapeType["FACE"])[0]
+f2 = geompy.GetOppositeFace( box, f1 )
+geompy.addToStudy( box, "box" )
+geompy.addToStudy( f1, "f1" )
+geompy.addToStudy( f2, "f2" )
+
+# compute 1D mesh
+mesh = smesh.Mesh( box )
+mesh.Segment().NumberOfSegments( 5 )
+mesh.Compute()
+
+# compute 2D mesh
+mesh.Quadrangle()
+mesh.UseExistingFaces(f1) # UseExistingFaces() allows using my2DMeshing()
+mesh.UseExistingFaces(f2)
+my2DMeshing( f1 )
+my2DMeshing( f2 )
+assert mesh.Compute()
+
+# compute 3D mesh
+mesh.Prism()
+assert mesh.Compute()
+
+\endcode
+
+Resulting mesh:
+\image html use_existing_face_sample_mesh.png
+
+*/
