Quote - Sigh. It seems nobody is going to look into the normals. I guess I'll have to do it myself.

My hypothesis is that Maya is exporting something with bad normals. The bug is in Maya, if there is a bug.

When you do that end-cap cut and paste, it isn't just that you're unwelding, you're also changing the normals.

The MayaCylinder that TheOwl posted has "vn" vertex normals in it. I don't have time to study them right now, but my guess is that one of them has a magnitude that isn't 1.0 or has a direction that is wrong.

The arrangement of polygon faces and welds doesn't seem to have anything to do with it. When I load and save from Blender (removing normals) the SAME topology is there. It renders fine.

er, Spanki's STOMP???
ok I just used the reorder faces to strip the normals information from the obj which fixes it. I did actually Confirm it for you.

you do know what Stomp does right? how it will sort the faces in the OBJ file, and put them in to order within the file (not the mesh) right? basically rewriting the OBJ from the ground up?