A bug of Paint transparent layers #82770

New Issue

zhouxiang · 2020-11-17T05:19:44+01:00

zhouxiang commented

2020-11-17 05:19:44 +01:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.71

Blender Version
Broken: version: 2.91.0 Beta, branch: master, commit date: 2020-11-16 21:13, hash: 906ff7b8fe
Worked: 2.90.1
Caused by b17cca6966

Short description of error
This is a new bug in 2.91, where every stroke of a transparent map leaves a black edge, but this did not happen in 2.90.
If you click "Save all Images", save this project and revert, the problem will disappear.
If you create a new transparent texture, this will happen again.

Exact steps for others to reproduce the error
Create a white background layer, then create a transparent layer, mix the two layers, connect the alpha of the transparent layer to the Mix node fac. then paint the color on the transparent layer.

#82770.blend

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.71 **Blender Version** Broken: version: 2.91.0 Beta, branch: master, commit date: 2020-11-16 21:13, hash: `906ff7b8fe` Worked: 2.90.1 Caused by b17cca6966 **Short description of error** This is a new bug in 2.91, where every stroke of a transparent map leaves a black edge, but this did not happen in 2.90. If you click "Save all Images", save this project and revert, the problem will disappear. If you create a new transparent texture, this will happen again. ![image.png](https://archive.blender.org/developer/F9307740/image.png) **Exact steps for others to reproduce the error** Create a white background layer, then create a transparent layer, mix the two layers, connect the alpha of the transparent layer to the Mix node fac. then paint the color on the transparent layer. [#82770.blend](https://archive.blender.org/developer/F9309424/T82770.blend)

zhouxiang commented

2020-11-17 05:19:44 +01:00

Added subscriber: @zhouxiang

zhouxiang commented

2020-11-17 05:39:17 +01:00

Save all images and revert this project.

![image.png](https://archive.blender.org/developer/F9308893/image.png) Save all images and revert this project.

Philipp Oeser commented

2020-11-17 09:37:21 +01:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2020-11-17 09:37:21 +01:00

Can confirm, checking.

Philipp Oeser commented

2020-11-17 09:49:21 +01:00

Caused by b17cca6966

Caused by b17cca6966

Jeroen Bakker was assigned by Philipp Oeser

2020-11-17 09:50:17 +01:00

Philipp Oeser commented

2020-11-17 09:51:30 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Jeroen Bakker commented

2020-11-17 11:38:02 +01:00

First impression is that the back edges originates when colors are converted twice from straight alpha to pre-multiplied alpha.

Philipp Oeser commented

2020-11-17 11:51:55 +01:00

In #82770#1056099, @Jeroen-Bakker wrote:
First impression is that the back edges originates when colors are converted twice from straight alpha to pre-multiplied alpha.

Dumb question: is there a way to prevent this with Generated images?

> In #82770#1056099, @Jeroen-Bakker wrote: > First impression is that the back edges originates when colors are converted twice from straight alpha to pre-multiplied alpha. Dumb question: is there a way to prevent this with `Generated` images?

Jeroen Bakker commented

2020-11-17 12:18:27 +01:00

Ignore my previous investigation. And something like dumb questions do not exist :-)

The root issue is a precision issue when non float sRGB images are used. Non float buffers aren't precise enough to store the pre-multiplied alpha. You can see that when you change the transparent image to a float image.

202011_T82770.mp4

Solution would be to store force 4 channel byte images to be stored in a more precise GPU buffer RGBA_16(F).

Ignore my previous investigation. And something like dumb questions do not exist :-) The root issue is a precision issue when non float sRGB images are used. Non float buffers aren't precise enough to store the pre-multiplied alpha. You can see that when you change the transparent image to a float image. [202011_T82770.mp4](https://archive.blender.org/developer/F9310440/202011_T82770.mp4) Solution would be to store force 4 channel byte images to be stored in a more precise GPU buffer RGBA_16(F).

blender-admin commented

2020-11-17 15:23:47 +01:00

This issue was referenced by d73130cc28

This issue was referenced by d73130cc287690539a0509a44abd4c85ffb30188

Jeroen Bakker commented

2020-11-17 16:11:23 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Jeroen Bakker closed this issue

2020-11-17 16:11:23 +01:00

Thomas Dinges added this to the 2.91 milestone 2023-02-08 16:20:08 +01:00

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A bug of Paint transparent layers #82770