def copy_mesh(src, dest):

vIndexMap = {}

# Copy the vertices, keeping track when indices change.

for v in src.vertices():

srcIndex = v.index()

destIndex = dest.vertices().add(

v.x(), v.y(), v.z(),

v.nx(), v.ny(), v.nz(),

v.u(), v.v()

)

if srcIndex != destIndex:

# NB: If the destination vertex index matches the source, we

# skip recording the entry, to save space in the map. Later, we

# leave indexes unchanged which are absent from the map.

#

# This scenario is actually quite common, because vertices are

# often numbered in natural order, with the first vertex having

# index 0, the second having index 1, etc., although it is not

# guaranteed.

vIndexMap.put( srcIndex, destIndex )

# Copy the triangles, taking care to use destination indices.

for tri in src.triangles():

v0src = tri.vertex0()

v1src = tri.vertex1()

v2src = tri.vertex2()

v0 = vIndexMap.get( v0src, v0src )

v1 = vIndexMap.get( v1src, v1src )

v2 = vIndexMap.get( v2src, v2src )

dest.triangles().add( v0, v1, v2, tri.nx(), tri.ny(), tri.nz() )