Operating system: Windows 10 & Debian 10 KDE
Graphics card: Intel HD620 integrated graphics
Broken: 2.93; 2.93.1; 3.0.0 alpha
Short description of error
- This only happens on versions of blender from 2.93 onwards.
- Any material where its final glossy roughness value is set between 0.0 and 0.003726621... is automatically shaded pure black, as if it had no shader at all.
- Diffuse roughness works properly.
- Viewport render view AND final render, on EEVEE, have the same problem
The following combinations cause a black material:
The problem even bypasses the mix node
In the following video I set roughness to 0 and shader goes full black. I switch to Cycles and the problem disappears:
The value "0.003726621" is rounded by Blender to 0.004.
The value "0.003726621" was found adding half an nth for every new digit:
0.00372663 yields a correct behaviour of the shader
0.00372662 results in a shadeless, black, material; add 0.000000005 and try again.
This number goes on and on.
Exact steps for others to reproduce the error
Use the default cube.
Apply any shader with a glossy roughness property.
Set glossy roughness to any value between 0 and 0.003726621.
This causes a shadeless material. Completely black.
The fact that I couldn't find any info about this bug at all on the internet tells me that my hardware is causing the problem. I did manage to find people with the same problem, but only a handful.