Win7 64bit, Quadro 4000
Broken: 2.73a, 2.74 RC2, both win x64
Short description of error
Ashikhmin-Shirley distribution of glossy shader at 0 roughness causes artifacts when background uses MIS. The artifacts look different depending on the device used (CPU or GPU) and depending on the kind of render (viewport or real render using F12).
Note: I know that for roughness 0 a glossy shader should be set to sharp and that MIS is bad when the background has just simple gradients, but setups like this happen sometimes...
Exact steps for others to reproduce the error
- Open attached .blend:
- Set viewport to rendered
- Try both CPU and GPU
- Try rendering
- Changing distribution on glossy shader, increasing roughness on glossy shader, turning off MIS on world all solve the problem