Not really, but why don't you just import a STL file for the TO-92 from 3Dcentral.com?
In PADS 9.1 the command is <File><3D Cell Import...>
Is your polygon on the proper layer? I have a note to check MG518767 for details on this topic.
I've been told by Mentor support that the 3D-Viewer is basically a poorly supported 'feature' that was carried over from another product. There are hints that Mentor will replace it soon with real 3D capability like Altium has.