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Colorspace inconsistency between color sampling operators #124401

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opened 2024-07-09 12:16:09 +02:00 by Simon Thommes · 4 comments
Simon Thommes commented 2024-07-09 12:16:09 +02:00
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System Information
Operating system: Linux-6.8.12-gentoo-x86_64-AMD_Ryzen_9_5950X_16-Core_Processor-with-glibc2.39 64 Bits, X11 UI
Graphics card: NVIDIA RTX A6000/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 550.90.07

Blender Version
Broken: version: 4.3.0 Alpha, branch: main, commit date: 2024-07-08 23:09, hash: bbcc720c1328
Worked: current 4.2 LTS

Short description of error
There is an inconsistency in the color space used for the back-transformation from display space between the sampling tool attached to the color picker and the modal operator on shift + x in Blender's draw modes. This is not the case in Blender 4.2.

Besides this issue, I'd also like to point out that neither of these two seem to actually do the proper back-transformation in all cases. In the steps I'm outlining to reproduce the issue neither of the two sampling operators retrieve the actual linear color values that are set. I would assume that both the AGX and the sRGB transformation are taken into account properly, so I'm not sure why that would not work.
This is another (separate) bug. or am I misunderstanding how the system is supposed to work?

Exact steps for others to reproduce the error

  • set world color to (0.5, 0.5, 0.5, 1)
  • set viewport to rendered mode
  • go to image texture paint mode
  • sample world with shift-x and inspect color (0.667, 0.667, 0.667, 1)
  • sample world with the sampling tool in the color picker (0.735, 0.735, 0.735, 1)
**System Information** Operating system: Linux-6.8.12-gentoo-x86_64-AMD_Ryzen_9_5950X_16-Core_Processor-with-glibc2.39 64 Bits, X11 UI Graphics card: NVIDIA RTX A6000/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 550.90.07 **Blender Version** Broken: version: 4.3.0 Alpha, branch: main, commit date: 2024-07-08 23:09, hash: `bbcc720c1328` Worked: current 4.2 LTS **Short description of error** There is an inconsistency in the color space used for the back-transformation from display space between the sampling tool attached to the color picker and the modal operator on `shift + x` in Blender's draw modes. This is not the case in Blender 4.2. Besides this issue, I'd also like to point out that neither of these two seem to actually do the proper back-transformation in all cases. In the steps I'm outlining to reproduce the issue neither of the two sampling operators retrieve the actual linear color values that are set. I would assume that both the AGX and the sRGB transformation are taken into account properly, so I'm not sure why that would not work. This is another (separate) bug. or am I misunderstanding how the system is supposed to work? **Exact steps for others to reproduce the error** - set world color to (0.5, 0.5, 0.5, 1) - set viewport to rendered mode - go to image texture paint mode - sample world with `shift-x` and inspect color (0.667, 0.667, 0.667, 1) - sample world with the sampling tool in the color picker (0.735, 0.735, 0.735, 1)
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 labels 2024-07-09 12:16:10 +02:00
Pratik Borhade commented 2024-07-10 07:14:54 +02:00
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Hi, thanks for the report. Can confirm

Hi, thanks for the report. Can confirm
Pratik Borhade commented 2024-07-10 07:30:33 +02:00
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From a quick look, significant difference in values started to occur between 25d4d645cdac - b59fbbe86546
With standard view transform on lite build, color values are close to equal.

From a quick look, significant difference in values started to occur between `25d4d645cdac - b59fbbe86546` With standard view transform on lite build, color values are close to equal.
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 labels 2024-07-10 07:31:01 +02:00
Pratik Borhade added this to the 4.2 LTS milestone 2024-07-10 07:31:06 +02:00
Pratik Borhade modified the milestone from 4.2 LTS to 4.3 2024-07-10 07:31:10 +02:00
Sergey Sharybin commented 2024-07-27 17:25:50 +02:00
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The eyedropper has been changed in #123408. This is to make it so the sampled color gives the same exact result after re-applying the color management. The value (0.735, 0.735, 0.735, 1) seems to be the correct one for sampling, as it gives the color matching (0.5, 0.5, 0.5, 1) after applying the color management.

Wouldn't really call it high priority bug, is more like the similar fix needs to be appleid to the Sample Color operator.

@LukasStockner is it something you feel comfortable to dig into?

The eyedropper has been changed in #123408. This is to make it so the sampled color gives the same exact result after re-applying the color management. The value `(0.735, 0.735, 0.735, 1)` seems to be the correct one for sampling, as it gives the color matching (0.5, 0.5, 0.5, 1) after applying the color management. Wouldn't really call it high priority bug, is more like the similar fix needs to be appleid to the Sample Color operator. @LukasStockner is it something you feel comfortable to dig into?
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Lukas Stockner self-assigned this 2024-08-04 22:36:01 +02:00
Sergey Sharybin added
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 labels 2024-08-07 19:31:02 +02:00
Sergey Sharybin commented 2024-08-07 19:32:13 +02:00
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Lowering priority.
It is a bit annoying issue, but it is jus another aspect of color picking that needs fixing. Is not a regression or anything like this.

Lowering priority. It is a bit annoying issue, but it is jus another aspect of color picking that needs fixing. Is not a regression or anything like this.
Bart van der Braak added
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 labels 2024-08-14 12:57:27 +02:00
Thomas Dinges removed this from the 4.3 milestone 2024-11-04 08:46:02 +01:00
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Reference: blender/blender#124401
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