Very good Question...
I don't have it installed right now.
I think stalker was one of the greatest games for S-3D! It had no artefacts I remember, so I either ignored the sky, or you get it correct by disabling sky effects
Edit: I hope this answers all your questions
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AMD x2 4200+ 2gb Dualchannel
GF 7900gs for old CRT with Elsa Revelator SG's
currently 94.24 Forceware and 94.24 Stereo with XP sp2!