It looks like Enhanced GLQuake and FitzQuake use the above method while FTEQW,Fuh/EZ/Joe/Qrack use the "r_viewleaf2 / r_oldviewleaf2" method [and with DP's code being rather unintelligible to mere mortals like myself].
Yeah, I don't want a performance hit if there is a better way, obviously.
I don't see this type of fix in TomazQuake or QIP Quake or GLQuake113 ... kind of weird considering I would have thought this fix or information would have been readily spread in the heavy Q1 engine modding days.
