This might not strictly be a bug but I will mention it anyway as it is as painful as one.
When exporting a model from Rhino via the FBX format, Rhino will create a copies of the same materials in the file.
Say I have 1000 cubes with a blue material.
When I export it to FBX and open it in ie. Blender, Max or Maya it will have 1000 materials all of which are exactly the same. They will be called “Blue Material”, “Blue Material_2”, “Blue Material_3”… “Blue Material_999”.
Are there some important reason why each object does not use the same object?
Right, in that case I’m sure I fixed this issue. In v5 indeed each use of the same material caused a new material instance in the FBX output. FBX does that no longer (nor OBJ, as it had the same problem).