Volumetric Clouds
The Standard/Photometric spectral atmosphere engine is capable of rendering highly realistic volumetric clouds with accurate lighting and volumetric shadows. Spectral cloud layers are three-dimensional, allowing you to create anything from thin ground fog to massive Cumulonimbus.
You can place as many layers as you need, at any height, and even combine spectral and standard, non-volumetric cloud layers (to add high altitude Cirrus, for instance). Spectral layers are created using any type of noise function, and provide a wide range of control over density, cover, sharpness, illumination, and even vertical profile.