In this simple scene there is a cube with an area lamp inside and a floor plane and a cube with simple materials applied.
The Outer cube has it's material set to be a volume.
The plan is to "see" the light rays within the volume.
In EEVEE:
In Cycles:
In RPR v2094:
I have attached the simple scene to this post.
Hopefully it fully demonstrates the issue that RPR is not rendering the volume at all.
Hi gelert,
Thanks for reporting. I can confirm Principled Volume does not seem to work.