Search keywords: simple fog, simple volumetric
VRaySimpleFog is an atmospheric effect that allows the basic simulation of participating media like fog, atmospheric dust and so. However it cannot simulate the scattering of GI and no maps can be used.
Emission - controls the fog emission (self-illumination). This parameter is used to to substitute the ambient illumination inside the fog, instead of using GI.
Color - defines the color of the fog when it is illuminated by light sources.
Color multiplier - a multiplier for the Color parameter
IOR - index of refraction for the volume. If simulating a fog inside an enclosed volume light rays entering or leaving the volume will be refracted based on this parameter
Bias - this parameter allows to change the way the Color is applied; by adjusting it you can make thin parts of the volume to appear more transparent than normal, or less transparent than normal.