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Copyright © 1998-2003,
Longbow Digital Arts.

As most of our systems run Windows NT here, I've never really bothered to play DirectX games such as Motocross Madness or Jane's F-15 on anything but a Voodoo card on a Windows 95/98 system, so I always just assumed that the ugly, purplish, artifacted black smoke from dust trails and explosions was merely a symptom of a 16-bit framebuffer. After testing with my own game on Voodoo, Verite 2200, G200, Permedia-2, and TNT (three of 'em, totally amazing card), I have come to a distinctly different conclusion.

Look at the composite screen shot below. It's a rather high-quality JPEG to preserve as much of the dither patterns as possible. The above shot was taken on a 3DFX Voodoo 1, though Voodoo 2 produces the same results. The below shot was taken on a Riva TNT, running in 16-bit color (just like the Voodoo), and ALL the other cards I have tested look almost identical to the TNT. The two shots went through ZERO image processing, except for clipping them out of their originals, adding text, and JPEG compressing.

Notice the extreme grid-like artifacting in the 3DFX version, and the way the smoke turns purplish and reddish toward the fringes. To me, this appears to be an extreme dither algorithm breakdown with high numbers of overlapping alpha-blended textures (it is only this bad when there are more than about 2 or 3 layers, but that's surprisingly easy to come by). My hunch (which may not be correct) is that 3DFX's much touted highly advanced dithering (to make 16-bit framebuffers usually look better than on other cards) falls flat on its face when dealing with alpha blending multiple layers over top of an already dithered framebuffer, whereas while the more mundane dithering algorithms used by every other chipset maker may look choppier with single-pass texturing, they seem to hold up much better with any significant amount of alpha-blended over draw.

If you're interested in seeing the raw, untouched BMPs in their entirety, here they both are in a ZIP archive. Download 3DFXBlend.zip (423 kb)

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Copyright 1998-1999 by Seumas McNally.
No reproduction may be made without the author's written consent.