True layered fog

[RCMaster]

A quick question :

Is TRUE layered fog (i.e. not with horizontal textured quads) something we can achieve only through high end cards (GeForce3 and above, Radeon ...) thanks to their "vendor added extensions" ? I need to implement such a fog effect for a flight sim, but the only fog I can produce with my GeForce 1 is "distance-from-point-of-view" based, thus making It hard to get the fog layered..

Should it be the case, do you know any good example of layered fog with textured quads ?

Thanks

[jwatte]

Use a 2D (or even 3D) texture, and the appropriate texgen, typically in eye space, to make the fog density depend on two dot products; typically dot product of position and up (for height-based) and position and camera vector (for the distance-based part).

Your artists can then paint the appropriate fog color & density function based on these two variables into the texture.