Heh, thanks, jim. From what I've read, it appears to be UE3. Google "Rainbow Six Vegas Unreal Engine" and you get a bunch of hits for UE3 (including that AT article), though it's technically possible that everyone's sourcing the same bad info and too lazy to double-check. I don't think it's a bad implementation of UE3 that's to blame for a current lack of AA, I think it's inherent in UE3's shadow rendering method. I don't know any details beyond what's in those links, but I thought I'd chip in to say it seems to be a limitation of the engine, not the implementation.