Python gpu bgl image drawing alpha problem #81289

New Issue

Philipp Oeser · 2020-09-29T12:52:19+02:00

Philipp Oeser commented

2020-09-29 12:52:19 +02:00

System Information
Operating system: Linux-5.8.4-200.fc32.x86_64-x86_64-with-fedora-32-Thirty_Two 64 Bits
Graphics card: GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.66

Blender Version
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-09-29 07:53, hash: 32d4a67017
Worked: 2.90.1
Caused by 536c2e0ec9

Short description of error
When drawing images with alpha using Python gpu bgl, alpha looks wrong

Exact steps for others to reproduce the error
Python gpu bgl image drawing alpha.blend

Open file
Execute script
Move mouse over 3D Viewport and rotate slightly to cause a refresh
Blender logo should appear over the Cube
Notice how alpha is drawn wrong, looks like this

Should look like this

Script is from here (only enabling GL_BLEND added)
https://docs.blender.org/api/master/gpu.html#d-image

Probably related: blender/blender-addons#80730 (BGL deprecation)

**System Information** Operating system: Linux-5.8.4-200.fc32.x86_64-x86_64-with-fedora-32-Thirty_Two 64 Bits Graphics card: GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.66 **Blender Version** Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-09-29 07:53, hash: `32d4a67017` Worked: 2.90.1 Caused by 536c2e0ec9 **Short description of error** When drawing images with alpha using Python gpu bgl, alpha looks wrong **Exact steps for others to reproduce the error** [Python gpu bgl image drawing alpha.blend](https://archive.blender.org/developer/F8935631/Python_gpu_bgl_image_drawing_alpha.blend) - Open file - Execute script - Move mouse over 3D Viewport and rotate slightly to cause a refresh - Blender logo should appear over the Cube - Notice how alpha is drawn wrong, looks like this ![image.png](https://archive.blender.org/developer/F8935644/image.png) Should look like this ![image.png](https://archive.blender.org/developer/F8935641/image.png) Script is from here (only enabling GL_BLEND added) https://docs.blender.org/api/master/gpu.html#d-image Probably related: blender/blender-addons#80730 (BGL deprecation)

Philipp Oeser commented

2020-09-29 12:52:19 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2020-09-29 12:52:56 +02:00

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

Philipp Oeser commented

2020-09-29 12:52:56 +02:00

Added subscriber: @fclem

Philipp Oeser commented

2020-09-29 12:52:56 +02:00

CC @fclem

Philipp Oeser commented

2020-09-29 12:55:19 +02:00

Added subscriber: @VilemDuha

Vilem Duha commented

2020-09-29 13:23:24 +02:00

Did a bit more deep-dive and in my tests:

drawing the first image or rectangle does work wrong. (both basically the same to what's here for 2d image and 2d rectangle: https://docs.blender.org/api/current/gpu.html)

however, this happens only for the very first image/rectangle drawn.

If I first draw one image , both rectangle and image work.
So there's something inside the image draw function that fixes the ogl settings -after it's been drawn. Sorry, oGL is really not my area, so this is amateur bug hunting ;)

Also, none of these helped in any reasonable way:
bgl.glClearColor(0.0, 0.0, 0.0, 0.0)

bgl.glEnable(bgl.GL_BLEND)

Did a bit more deep-dive and in my tests: drawing the first image or rectangle does work wrong. (both basically the same to what's here for 2d image and 2d rectangle: https://docs.blender.org/api/current/gpu.html) however, this happens only for the very first image/rectangle drawn. If I first draw one image , both rectangle and image work. So there's something inside the image draw function that fixes the ogl settings -after it's been drawn. Sorry, oGL is really not my area, so this is amateur bug hunting ;) Also, none of these helped in any reasonable way: bgl.glClearColor(0.0, 0.0, 0.0, 0.0) ``` bgl.glEnable(bgl.GL_BLEND)

Philipp Oeser commented

2020-09-30 18:13:00 +02:00

Ah, I've seen you've gotten around this by blender/blender-addons@768a8cfc35, still this should be fixed or documented though

Vilem Duha commented

2020-10-01 10:04:21 +02:00

Yes, and I feel ashamed for the super-hacky fix, which I remove once the fix is there or find out a better way. I just don't know what other OGL settings to reset, probably setting some OGL defaults would fix the issue.

Philipp Oeser commented

2020-10-01 19:32:09 +02:00

Dare setting this to High, not sure if we can be in this "half-broken" state until Vulkan is here, just checking what the plan is here @fclem ?

blender-admin commented

2020-10-08 16:19:42 +02:00

This issue was referenced by f12b0373f3

This issue was referenced by f12b0373f322b710b9fa5cebb67bdf363ff90e9f

Clément Foucault commented

2020-10-08 16:38:00 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Clément Foucault closed this issue

2020-10-08 16:38:00 +02:00

Clément Foucault self-assigned this 2020-10-08 16:38:00 +02:00

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Python gpu bgl image drawing alpha problem #81289