Hi there,

A simple tip to create and render volumetric fog and other similar effects with Iray.
You can download two MDL package from NVIDIA.
vMatrials pack: https://www.nvidia.com/en-us/design-visualization/technologies/vmaterials/
MDL Material Exchange pack (under the Seamless Material Exchange paragraph): https://www.nvidia.com/en-us/design-visualization/technologies/material-definition-language/

First some facts. Iray currently doesn’t support inhomogeneous volumes. But you can create homogeneous ones (means constant density). In some cases (fog, dusty air, etc.) it will look grate but in others (smoke) not that much.

• Create a geometry (for testing a simple cube is enough)
• Scale it up to encompass the whole scene
• Assign an ifmMDLMaterial to it.
• Find a Subsurface Scattering mdl (for example mdl::LwBase::SubsurfaceScattering).
• Set the Diffuse Weight to 0, and the IOR to 1
• Change the Subsurface Color.
•  Change the SubsurfaceScatterDistance and the SubsurfaceAbsorbDistance to your liking.
• Render

Cheers, D