Hi sneather, IGES does have the concept of a "Level" which is basically the same as a layer. I don't know for sure that Alias writes that information out to the IGES file but if it does then the layer grouping should come through too with IGES format. You'll lose the specific name, they'll be named things like "Level 1", "Level 2", etc... in MoI because an IGES level is just a number and not a text name though.

But it's also possible that the way trim curves work in IGES will more closely match how Alias structures them itself so if you're running into problems with things trimmed incorrectly that may possibly be lessened in this particular circumstance using IGES.

- Michael