BUG: vtkOBJImporter does not handle multiple groups using same material
The original code assumed that each material could only be used by one actor (group). There is no mention of this restriction in the Wavefront obj specification. The solution is to use a map of vectors to map between material and actors. New test added. BUG: vtkOBJImporter fails if vt are present but texture indices not present Another bug was discovered while addressing the original issue. If texture coordinates are present via "vt" command but texture indices are not defined for the faces, the actor was skipped. The solution is to add a boolean variable that indicates whether texture indices are defined. If there are no texture indices, do not add TCoords to the PointData.