Volume Scatter bug

[Under-J]

Issue

Volume Scatter node (maybe any volume node?)) isn't working as expected when using multiple materials, each with its own volume, on an object.

Steps to Reproduce

1. Assign a material with volume on a part of an object.
2. Assign another material with a different volume on another part of the same object.
3. Render

System Setup (Environment)

RTX 4070 12GB, i5-10400, Windows 11, Blender 3.5.1, RPR v3.6.9

Detailed Description

Make it match Cycles.

Cycles, expected results:

RPR results show that the first volume item in the Active Material overrides all other volumes and even materials with no volume. If you rearrange the order of the materials, it affects the volume of the entire object.

RPR, bad results, half of cube (it is really 2 cubes joined, so 1 cube), its volume is pink, the other one is blue, but with RPR both are pink.

If i separate them by material they work fine. just as expected:

Another detail is that if there is another material without Volume as the first material in the Active Material Index, the volume in the rest of the materials disappears.

Volume Bug 2.zip