Volumetric Fog

When you want to do volumetric fog it would be nice to have some functions to declare 4 positions in 3d space that the fog will be in. That would be very cool when you want to do i.e a fogged floor or something like that.
Is this possible???

Alternatively, how about being to specify the fogging vector? F’rinstance, instead of fog intensity being based on distance from the viewer (which is approximated as Z by most implementations), you could base fog intensity on the (negative) Y axis to get ground mist, cloud layers and so on.

Volumetric fog patches would take a fair bit of work to implement - like lighting, it’s really a scene-level thing rather than an immediate-mode primitive.

You must base fogging on the distance from viewer because you need to know how much fog the viewer is looking through.

To be a little more general, you have to know the distance through the fogging volume that the viewers line of sight has passed. If the fogging volume is the whole scene then the two are equivilent.

Why not throw in like a volumetric fog material (or something like that) and you can render the fog using a texture as an opaque source. This is what most 3D rendering programs do, might be very slow, but it sure looks really nice, instead of having this constant fog all over.