Operating system: Windows-10 64 Bits
Graphics card: GeForce GTX 1070 NVIDIA 419.67
CPU: AMD Ryzen 7 1700X
Broken: version: 2.80 (sub 57), branch: master, commit date: 2019-04-16 06:07, hash: rBedc1b0167518
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
- Launch Blender, delete light.
- Add 3-4 level subdivision surface modifier to the cube and enable smooth shading.
- Add Glass material to that object and set low roughness value (below 0.2)
- Add Light inside that object.
- Bring camera closer and render.