Fogging problems: Matrox MGA-G200 and STB Velocity 4400

OpenGL OpenGL: Advanced Coding
1

I have the following lines of code in an application:

glEnable(GL_FOG);
glFogf(GL_FOG_MODE, GL_EXP2);
glFogf(GL_FOG_DENSITY, 0.3f);
glFogfv(GL_FOG_COLOR, fogColor);

In addition, the app is using texturemapping with GL_DEPTH_TEST enabled.

This all works perfectly fine with Creative 3D Blaster Annihilator Pro (GeForce 256), but fails with Matrox MGA-G200 and STB Velocity 4400 (TNT) with the latest drivers. I haven’t yet been able to test it with Voodoo.

Disabling fogging makes everything run ok. Any ideas about the solution?

2

Maybe you should try to put the
glEnable(GL_fOG) at the end of the fog declarations, i dont know if this solves your problem. But i have it that way and it works on my G200.

3

The problem is that I don’t have G200 myself, so it’s kinda hard to test it I always have to try it on other computers. Have you tried it the other way?

4

No i haven’t tried it, but i will as soon as i get back to my house. And i will post a reply later.

5

hmmm both “methods” worked just fine…
then i cant help you, sorry.

6

It seems that the vendors have different implementations of fogging. With a lower fog density it worked fine with those TNT cards.

I think this is pretty stupid, you can’t guarantee that exponential fog will look the same (or work at all) on different cards. I don’t know if linear fog is any better, at least I hope it works equally well on different hardware.

7

Have this weird fog problem too…
On my GeForce2 MX everything’s fine.
On other cards (Matrox, TNT2 M64) weird
fog covering entire ground appears…
Maybe it’s tesselation (1 huge quad , maybe glClearColor doesn’t match fog color,
maybe Bill Gates’
crafty designs, maybe moon phases, but why oh why does it work on my card?

8

This may have to do with per-pixel vs. per-vertex fog. Higher tessellation will improve the quality of per-vertex fog.

We do per-pixel fog on GeForce products.

  • Matt