When using VRayEnvironmentFog with VRayEnvironmentFog with standard 3ds Max lights (Omni, Spot, etc.), you need to turn on the Atmosphere shadows option in order to get proper self-shadowing for the volume.
When using VRayEnvironmentFog, it is recommended to turn on the Optimized atmospherics evaluation option in the System rollout of the V-Ray Render Settings.
In contrast to the native 3ds Max Volume Light atmospheric effect, VRayEnvironmentFog covers the entire volume specified by the Fog height parameter or the listed Gizmos - its effect is not limited to the cone or area of influence of the particular lights that affect the fog.
When using VRayEnvironmentFog with weak VRayLights, it may be necessary to turn down the Cut-off threshold parameter of the lights. The default value for this parameter works fine for surfaces, but for volumes, where a lot of weak light contributions are added together, it may produce a visible sharp boundary where the light calculations stop.
You can use the various 3ds Max procedural textures to modify volume properties, including Gradient maps and Falloff maps in Distance blend or Object mode.
V-Ray does not have separate global illumination maps for volumetric rendering. Instead, all GI engines (the irradiance map, light cache, global/caustics photon maps) have been modified to support volumetric data.
3D textures are set to Object XYZ mode by default. This may need to be changed to World XYZ if the texture is to be assigned to fog in the scene environment.
V-Ray GPU render does not support Mapping options yet.
In V-Ray GPU to set a VRayEnvironmentFog gizmo, the geometry object should be hidden or set to not "Renderable" in Object properties.
