I have to confess I didn't even think of that thread when I wrote the script. It just seemed natural to cache faces by group and material and write them out at the end.

If anyone's interested, I'm happy to share that script. I'd just have to remove the Wings-specific bits or at least make them optional. Wings does some weird things like adding the object name to the group name, which the script fixes in the same run.

I've started to work on a more extensive .obj file cleanup program written in Scala. One of its purposes will be to transfer information between objects that have the same topology but possibly moved and re-ordered vertices. That should be very useful for making morphs with programs such as Wings that do not support direct symmetric editing, but also for patching UV maps back in after editing figures and such things.

-- I'm not mad at you, just Westphalian.