Following NeHe''s new (and rather great) tutorial on using GL_EXT_fog_coord, I was wondering about various fallback paths. It''s all nice and fine if you have drivers that support GL_EXT_fog_coord, and from what I''ve looked at, it''s supported well enough to implement (plus it''s fast :D). So my question is what you guys think I should do about simple volumetric fog in a scene. It will become a multiplayer game and as a result, I need to attempt to get a similar effect regardless of the card for a level playing field. Should I consider other extentions? Is native fog fast enough? If nothing else, this thread might help someone who hasn''t explored the options on the fog topic

The EXT_fog_coord extensions is supported almost as good as multexturing.

Anyway, it can be emulated by multipass VCI (vertex color interpolation) which simply consists on rendering all models in two passes, where the second pass is not lighted / not textured / not colored and where you call glColor4f(fog_red, fog_green, fog_blue, fog_coord) for each vertex instead of glFogCoordf(fog_coord)

AFAIK there is another problem with fog coords. VAR doesn''t support them. If you are using VAR what you probably are then using fog coords will disable this extension. So you have to make a decision whether use VAR or fog coords but you can''t use them together.

If I''m not mistaken, when you say VAR you mean Vertex Arrays... And in that case, yes you can use them. glFogCoordPointerEXT().

My card supports multitexturing but not hardware fog, so I cant see the demo

But how about making fog with particles? Has anyone tried that before?

VAR means Vertex Array Range. It is an NVIDIA-specific extension that accelerates VA (Vertex Array) transferts through the pipeline by using AGP or video memory.

I don''t think it is a problem since VBO are now complete (and implementations begin to appear) and that extension does not mention a conflict with fog arrays.

James : what graphics card do you have, and did you install the latest drivers for it ?

Ok, thanks for correcting me about the Vertex Array Range thing.... I know I''ve heard a million times before, but I must have just forgotten... hehe.

I have a KYRO card, with the latest drivers...
But the problem is that the company that was making drivers for the card I have were bought up, or something like that, so they have stopped making drivers!
That really pissed me off!
But I''ll probably by something decent sometime soon =)

Ah ok, how old is the driver ?

Lol, these drivers are a little old. 17-10-2002 was the last time they were updated.

Lol, the card supports eight-layer multitexturing, but not hardware fog...

vincoof, could you tell me more about VCI? I had a look about google and couldn''t find anything useful.
If it''s a multipass solution will it not kill my framerate on slower systems even in small scenes?

The whole reason for my starting this thread is to weigh up the options as a feasibility study.
I think it would be useful to see a comparison in terms of performance vs compatibility...