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Low Roughness Value on Glass Material Causes Artifacts with GPU+CPU Renders
Open, Confirmed, MediumPublic


System Information
Operating system: Windows-10 64 Bits
Graphics card: GeForce GTX 1070 NVIDIA 419.67
CPU: AMD Ryzen 7 1700X

Blender Version
Broken: version: 2.80 (sub 57), branch: master, commit date: 2019-04-16 06:07, hash: rBedc1b0167518
Worked: 2.79.6

Short description of error
Light inside an object that has glass material with low roughness causes blocky artifacts on GPU+CPU Cycles renders. It renders fine either in GPU or CPU renders.

Exact steps for others to reproduce the error

  1. Launch Blender, delete light.
  2. Add 3-4 level subdivision surface modifier to the cube and enable smooth shading.
  3. Add Glass material to that object and set low roughness value (below 0.2)
  4. Add Light inside that object.
  5. Bring camera closer and render.



Event Timeline

Confirmed here. Linux Mint 19.1, GTX 1080ti

I noticed that the artefacts completely go away when you set the "Filter Glossy" to 0.

Brecht Van Lommel (brecht) triaged this task as Confirmed, Medium priority.