I've come to a bit of a problem here that I really should have thought about months ago, but didn't (because, well...I'm an idiot :-D). I've got 2 sets of brushes. The first set are the brushes that are used to perform CSG operations, along with the associated operation that they perform. The second set is the brushes, post-operation. Well, that's not entirely accurate; what I've got are the addative brushes, sans subtracted pieces. Now, I'm coming to a bit of a problem when it comes to face selection. I want to make it so that when I select one polygon, it'll select all polygons that were a part of the original polygon in the original brush (ala UnrealEd). So, I'm trying to come up with a good way to do it. My first thought was that I could store a pointer to the original brush / face that the polygonal fragments came from. This seems to be fairly reasonable, and would require a mere extra pointer for each poly. I've also considered using a depth-based system to do the ops (as opposed to the math-based ops that i'm doing now) (not general programming related, I know, I know), but I can't imagine how that could possibly be done with any kind of efficiency. Hrmph. Anyone with some prior experience doing something along these lines have any advice?

I keep the originals around for this purpose. Plus I only display originals in the ortho views since the cutup cells would be a mess from my experience. UnrealEd must also keep originals because they don't look cut up in the view do they? Been a while since I used it.

UnrealEd keeps the originals, yes, for the ortho views, or when a brush is "selected".