Alpha display problem in the Image Editor #80326

Closed
opened 2020-09-01 15:24:07 +02:00 by Steffen Dünner · 14 comments

System Information
Operating system: Linux-5.4.0-45-generic-x86_64-with-debian-bullseye-sid 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.51.06

Blender Version
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-09-01 12:39, hash: 526fbdec3b
Also broken in the 2.90 and 2.83.5 LTS!

Short description of error
The Alpha channel display in the Image Editor gets completely garbled if you switch it to show only the Alpha channel, change the current frame by pressing cursor left or right and the pressing F12 again. This is what the Alpha should look like:image.png
And here's how it looks after changing the frame:
image.png

Exact steps for others to reproduce the error

  • Open the attached blend file (basically an empty scene with the default cube):
    Alpha_Problem_v01.blend
  • Press F12 to render and to open the Image Editor. Everything looks fine.
  • Switch the Image Editor to show the Alpha channel:
    image.png
  • Press cursor right or left to change the current frame
  • Press F12 again
  • The Alpha is a total mess

This happens in 2.83.x, 2.90 and the latest master. Both in CPU and GPU mode.
When saving the garbled image from the Image Editor (to a PNG e.g.) the Alpha is fine. So it looks to me like it's only a display problem?

**System Information** Operating system: Linux-5.4.0-45-generic-x86_64-with-debian-bullseye-sid 64 Bits Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.51.06 **Blender Version** Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-09-01 12:39, hash: `526fbdec3b` Also broken in the 2.90 and 2.83.5 LTS! **Short description of error** The Alpha channel display in the Image Editor gets completely garbled if you switch it to show only the Alpha channel, change the current frame by pressing cursor left or right and the pressing F12 again. This is what the Alpha should look like:![image.png](https://archive.blender.org/developer/F8829777/image.png) And here's how it looks after changing the frame: ![image.png](https://archive.blender.org/developer/F8829779/image.png) **Exact steps for others to reproduce the error** - Open the attached blend file (basically an empty scene with the default cube): [Alpha_Problem_v01.blend](https://archive.blender.org/developer/F8829785/Alpha_Problem_v01.blend) - Press F12 to render and to open the Image Editor. Everything looks fine. - Switch the Image Editor to show the Alpha channel: ![image.png](https://archive.blender.org/developer/F8829786/image.png) - Press cursor right or left to change the current frame - Press F12 again - The Alpha is a total mess This happens in 2.83.x, 2.90 and the latest master. Both in CPU and GPU mode. When saving the garbled image from the Image Editor (to a PNG e.g.) the Alpha is fine. So it looks to me like it's only a display problem?

Added subscriber: @SteffenD

Added subscriber: @SteffenD

Added subscriber: @jack.herbert

Added subscriber: @jack.herbert

Here with 2.91, I can reproduce without even changing frame. Just open Blender, enable Transparency and render. Then switch render viewport to Alpha and render again.
Note that it only happens with Cycle and the alpha channel actually seems fine when switching back to Colour and Alpha mode.

Here with 2.91, I can reproduce without even changing frame. Just open Blender, enable Transparency and render. Then switch render viewport to Alpha and render again. Note that it only happens with Cycle and the alpha channel actually seems fine when switching back to Colour and Alpha mode.

Added subscribers: @fclem, @mano-wii

Added subscribers: @fclem, @mano-wii

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

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

I can confirm in Cycles, because of the tile rendering.
The problem happens when you view the Alpha channel before rendering is complete.
So it must be a problem to update the image.

I can confirm in Cycles, because of the tile rendering. The problem happens when you view the Alpha channel before rendering is complete. So it must be a problem to update the image.

Removed subscriber: @fclem

Removed subscriber: @fclem
Member

Added subscriber: @Jeroen-Bakker

Added subscriber: @Jeroen-Bakker
Member

In 2.91 the image drawing was redone D8234: Use DrawManager for Image/UV Editor I am not able to reproduce this issue, @mano-wii, can you recheck?

In 2.91 the image drawing was redone [D8234: Use DrawManager for Image/UV Editor](https://archive.blender.org/developer/D8234) I am not able to reproduce this issue, @mano-wii, can you recheck?

Yes, for me too, the problem is resolved with a more recent build

Yes, for me too, the problem is resolved with a more recent build
Member

Added subscriber: @lichtwerk

Added subscriber: @lichtwerk
Member

Changed status from 'Confirmed' to: 'Resolved'

Changed status from 'Confirmed' to: 'Resolved'
Philipp Oeser self-assigned this 2020-09-30 12:54:40 +02:00
Member

Seems resolved, @SteffenD, @mano-wii, please comment again if issues persist.

Seems resolved, @SteffenD, @mano-wii, please comment again if issues persist.

Great! Thanks. So far it's looking good. I'll report back as soon as something weird happens.

Great! Thanks. So far it's looking good. I'll report back as soon as something weird happens.
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Reference: blender/blender#80326
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