Can anyone explain this? Every generation of Nvidia card has had this problem that I've seen. I've seen it ever since the TNT, and now I'm seeing it on my GeForce 256 and Tod's GeForce 4.

Every time a game does a "smoke" or "mist" effect, the frame rate hitches and sputters. I'm not talking about wide-area volumetric fog, I'm talking about stencil-style localized smoke tricks. Examples to follow below...

This seems to be totally engine-independent. For instance, back in the TNT days I saw it in certain areas on the Quake-engine game Half-Life. On the GeForce cards, I'm seeing in the new games Arx Fatalis and Unreal II.

Examples:

Arx Fatalis: Certain scenes where there is supposed to be light streaming into a prison cell through the bars in the window. They've added a sort of "dust-hanging-in-the-air" trick as an atmospheric effect so that you can see the light shining through the bars. This causes the frame rate to hitch and sputter, even when you're really far down the hallway and the effect amounts to something like four pixels total on the screen. It even affects the CPU, screwing up your control input, making you over-rotate or slide past a doorway.

Unreal II: Early in the game, your head tech is giving you a tour of the ship, and he's smoking a cigarette as he leads you around the ship. Any time he's facing you and you see the smoke effect coming off of the cigarette, the frame rate hitches and sputters.

Half-Life: Any time there are multiple stencils on the wall, such as blood spatters combined with weapon hit stencils, if you walk up close to them so that they fill most of the screen, your frame rate stutters like crazy even though there's pretty much only one polygon on the screen. This isn't technically a smoke effect, but I think it might be related. I'm guessing that the wall stencils in Half-Life were done with a similar programming style as the smoke effects in these other games. And I also seem to recall certain smoke effects in the game causing the same problem.

Anyone have any idea why this happens, and if there are work arounds?