Image of the viewport can no longer be obtained via glReadPixels in Python. Gives strange results since 2.83 #80471

New Issue

Martin Grewe · 2020-09-04T15:36:35+02:00

Martin Grewe commented

2020-09-04 15:36:35 +02:00

System Information
Operating system: Arch Linux 5.8.5-arch1-1
Graphics card: Intel i7-8665U

Blender Version
Broken: since 2.83
Worked: till 2.82
Short description of error

In Python, we get an image of the viewport from within an registered draw handler routine using:

viewport = bgl.Buffer(bgl.GL_INT, 4)
bgl.glGetIntegerv(bgl.GL_VIEWPORT, viewport)
width = int(viewport[2])
height = int(viewport[3])
image = np.zeros([height, width, 4],dtype=np.uint8)
buffer = bgl.Buffer(bgl.GL_BYTE, image.shape, image)
bgl.glReadPixels(0, 0, width, height, bgl.GL_RGBA, bgl.GL_UNSIGNED_BYTE, buffer)

It worked fine till 2.82, as shown here

However, it gives blackish colors of the objects in the viewport since 2.83:

**System Information** Operating system: Arch Linux 5.8.5-arch1-1 Graphics card: Intel i7-8665U **Blender Version** Broken: since 2.83 Worked: till 2.82 **Short description of error** In Python, we get an image of the viewport from within an registered draw handler routine using: viewport = bgl.Buffer(bgl.GL_INT, 4) bgl.glGetIntegerv(bgl.GL_VIEWPORT, viewport) width = int(viewport[2]) height = int(viewport[3]) image = np.zeros([height, width, 4],dtype=np.uint8) buffer = bgl.Buffer(bgl.GL_BYTE, image.shape, image) bgl.glReadPixels(0, 0, width, height, bgl.GL_RGBA, bgl.GL_UNSIGNED_BYTE, buffer) It worked fine till 2.82, as shown here ![till2.82.jpg](https://archive.blender.org/developer/F8840476/till2.82.jpg) However, it gives blackish colors of the objects in the viewport since 2.83: ![since2.83.jpg](https://archive.blender.org/developer/F8840477/since2.83.jpg)

Martin Grewe commented

2020-09-04 15:36:36 +02:00

Added subscriber: @mgrewe

Martin Grewe changed title from ~~Offloading of rendered viewport gives strange results since 2.83~~ to Image of the viewport obtained via Python gives strange results since 2.83

2020-09-04 16:04:01 +02:00

Philipp Oeser commented

2020-09-05 10:22:12 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2020-09-05 10:22:12 +02:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Philipp Oeser commented

2020-09-05 10:22:12 +02:00

Just checking if I understand this correctly:

I've put your code [not exactly the same, left numpy out of play here for the time being] into an operator which seems to give correct results here (no black/unshaded object afaict):
#80471.blend

Does this fail for you as well?
If not, please provide a .blend file with your code failing -- with the complete code to run from the Text Editor (including saving the image or dumping the data into a blender Image datablock)

Just checking if I understand this correctly: I've put your code [not exactly the same, left numpy out of play here for the time being] into an operator which seems to give correct results here (no black/unshaded object afaict): [#80471.blend](https://archive.blender.org/developer/F8843421/T80471.blend) Does this fail for you as well? If not, please provide a .blend file with your code failing -- with the complete code to run from the Text Editor (including saving the image or dumping the data into a blender Image datablock)

Martin Grewe commented

2020-09-05 13:28:31 +02:00

Hi Philipp,

thanks for the reply. Please find an updated blend file attached which should give what I tried to describe above. You might need to toggle "Generated Image".

#80471.blend

2.82:

2.90:

Hi Philipp, thanks for the reply. Please find an updated blend file attached which should give what I tried to describe above. You might need to toggle "Generated Image". [#80471.blend](https://archive.blender.org/developer/F8843894/T80471.blend) 2.82: ![2.82.jpg](https://archive.blender.org/developer/F8843899/2.82.jpg) 2.90: ![2.90.jpg](https://archive.blender.org/developer/F8843901/2.90.jpg)

Clément Foucault commented

2020-09-13 16:57:43 +02:00

Added subscriber: @fclem

Clément Foucault commented

2020-09-13 16:57:43 +02:00

This is expected. We separated the overlay drawing and the render in 2.83. So glReadPixels will return the overlays color only (because the callbacks are rendered on the overlay framebuffer).

We still have to figure how to give access to the render color buffer.

It is unpractical for us to give access to the final framebuffer as it is now the window framebuffer.

This is expected. We separated the overlay drawing and the render in 2.83. So glReadPixels will return the overlays color only (because the callbacks are rendered on the overlay framebuffer). We still have to figure how to give access to the render color buffer. It is unpractical for us to give access to the final framebuffer as it is now the window framebuffer.

Clément Foucault commented

2020-09-13 16:59:47 +02:00

Changed status from 'Needs User Info' to: 'Confirmed'

Martin Grewe commented

2020-09-14 09:53:49 +02:00

Thanks for investigation. I hope the access can be done fast as we use it as an option to stream the viewport in a time-critical application. Pl. let me know if I can be of any help, e.g. testing. Cheers, Martin

Campbell Barton changed title from ~~Image of the viewport obtained via Python gives strange results since 2.83~~ to Image of the viewport can no longer be obtained via glReadPixels in Python. Gives strange results since 2.83

2020-09-15 08:20:05 +02:00

Fabien commented

2020-10-29 08:51:44 +01:00

Added subscriber: @chafouin

Jose Conseco commented

2020-12-11 21:32:31 +01:00

Added subscriber: @JoseConseco

Roman Markov commented

2021-02-26 22:02:26 +01:00

Added subscriber: @unwave

Martin Grewe commented

2021-09-14 13:06:10 +02:00

Hi all, just wanted to push this since a way to get the viewport image is still needed.

Is there maybe another way to get access to the rendered image? I want to avoid offscreen rendering due to additional overhead.

Hi all, just wanted to push this since a way to get the viewport image is still needed. Is there maybe another way to get access to the rendered image? I want to avoid offscreen rendering due to additional overhead.

Christian Brinkmann commented

2021-11-13 09:25:40 +01:00

Added subscriber: @p2or

Will commented

2022-04-25 10:52:44 +02:00

Added subscriber: @Will-43

Philipp Oeser removed the

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Image of the viewport can no longer be obtained via glReadPixels in Python. Gives strange results since 2.83 #80471