Hey OpenGL gurus!

I'm a OpenGL-n00b and have a little problem with 3D-smoke. I have billboards with 32bit textures, all z-sorted ofcourse. Now the problem seems to be that when the billboards are very near to each-other, the blending gets messed up.

The following screenshot illustrates the problem:



I've done some drawing on it so explain what's happening.

I've played a lot of FPS-games, that use 3D-smoke where these artifacts are not occuring, so it is probably my fault

Ah, that makes me think about the z-buffer... (doh) it has a presicion of only 24 bits... (ATi-card)

Settings were: near 0.001F / far 8192.0F

Narrowing them solved it! Thx!

Hm, interesting. You see I'm a n00b here. Now I enable it for the terrain and disable it for the smoke. For this kind of smoke it turns out it doesn't matter at all whether I z-sort them or not (who cares which grey cloud is rendered first if they are all the same color and blended). For other kinds of particle-engines or 3d-blended objects the z-sorting is important so I guess I'll keep it anyway. The z-sorting isn't a real performance hit, but disabling the depth-buffer increased performance by 33% when the smoke fills the whole screen. (150fps -> 200fps)

Thanks again for all help. I guess I have to read that Redbook someday before doing anything serious in OpenGL.