Using a simple substrate glass material in pathtracer produces artifacts in the form of colored streaks across the object and causes a lot of noise (I have included the material in the zip).
We were able to narrow the issue down to the transmittance color input of the Substrate Transmittance-to-MFP node. Using flat colors (solid color, stripes etc.) works as expected but as soon as any smooth color transitions or gradients are introduced, the artifacts start showing up (refer to the screenshots in the attachment).
-image A - posterization:1, depth:50
-image B - posterization:4, depth:50
-image C - posterization:100000, depth:50
Substrate.zip(922 KB)
