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When world color is black, white objects under white lights are rendered as black
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Description

System Information
Operating system: Linux-4.15.0-130-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: AMD TURKS (DRM 2.50.0 / 4.15.0-130-generic, LLVM 10.0.0) X.Org 3.3 (Core Profile) Mesa 20.0.8

Blender Version
Broken: version: 2.91.0, branch: master, commit date: 2020-11-25 08:34, hash: rB0f45cab862b8
Worked: Blender 2.79 (possibly newer, these 2 versions are all I have).

Short description of error
When world color is black, white objects under white lights are rendered as black.

Exact steps for others to reproduce the error

  1. Open Blender 2.91 with default cube, light and camera.
  2. Go to World Properties tab, change Surface color of world to black.
  3. Press F12.
  4. The cube will be rendered totally black, even though it is a pale material with a light on it. This is not how lighting works, black does not project onto surfaces and override light.

Repeating these steps in Blender 2.79 produces correct results, rendering a visible pale cube.

Event Timeline

Rendering correctly(as it should) on windows in 2.91 and 2.92 Alpha(both cycles and eevee)

Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: Intel(R) UHD Graphics Intel 4.5.0 - Build 26.20.100.7323

Following Saran's example I just tried on Windows now too and the cube renders correctly there.

So this is definitely a bug on the Linux version, because I am the same user and get different results on the different platforms.

According to this site, the AMD turks GPU is a Terrascale 2 GPU and is thus not officially supported in Blender and as a result bugs like this can occur. See the list of supported hardware here: https://www.blender.org/download/requirements/

Installing the latest graphics driver sometimes helps to make such GPUs work, see here for more information. https://docs.blender.org/manual/en/dev/troubleshooting/gpu/index.html

If that doesn't help, you can use older versions of Blender like 2.79: https://www.blender.org/download/previous-versions/

Thanks, Alaska.

Blender uses GPU for its screen display, but does it use GPU to render PNG files? Because that's where the problem happens.

If you're using EEVEE, then yes, it uses the GPU to render images like PNG files. If you're using Cycles, you will need to explicitly tell it to use the GPU.

I cannot reproduce this and the GPU is indeed not officially supported. I will close this for now.

Alaska's suggestion of switching to cycles worked, proving it is only a problem when using the GPU.

Now I have a satisfactory workaround and can proceed.

I hope Blender keeps its software rendering option forever. GPUs are fast but not standard across all machines so not always reliable.