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Maniphest T63270

cryptomatte file output produces incorrect matte image
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Description

System Information
Operating system: Windows 10 Pro 64 Bit
Graphics card: GTX 750 TI

Blender Version
Broken: blender-2.80-a813e259d630-win64, master, 2019-04-03

Short description of error
The matte image written to disk is wrong after the file output node is changed

Exact steps for others to reproduce the error

  1. load the file "archiviz5_bugtest1.blend"
  2. render once
  3. change the "File Output" node. Click on "Add Input", connect Depth (or Alpha) from "Render Layers" to Image_002.
  4. render once more. The "Matte" image_001 written to disk now is wrong ("C:\blender-output\Image_0010004.png"). The matte image displayed in blender is still correct however.

If the edited file is saved now and blender is restarted, then the rendering will be correct again

Also, even if the "File Output" node is restored to its previous state (the additional file output is removed),
then the rendering will always be wrong until blender is restarted.

archiviz5_bugtest1.blend221 MBDownload

Related Objects

Event Timeline

afaenger (afaenger) created this task.Apr 4 2019, 9:29 AM
Sebastian Parborg (zeddb) assigned this task to Jeroen Bakker (jbakker).Apr 4 2019, 4:02 PM
Sebastian Parborg (zeddb) lowered the priority of this task from 90 to 50.
Sebastian Parborg (zeddb) added subscribers: Jeroen Bakker (jbakker), Sebastian Parborg (zeddb).

@Jeroen Bakker (jbakker) feel free to reassign if this is not for you.

Jacques Lucke (JacquesLucke) added a subscriber: Jacques Lucke (JacquesLucke).Apr 5 2019, 2:48 PM

@afaenger (afaenger), are you able to reproduce the behavior in a new, smaller file?

afaenger (afaenger) added a comment.Apr 5 2019, 3:01 PM

No, not tried as I've basically no experience with blender. I've just started to play around a bit and do some tutorials. The file is was downloaded from the 2.8 demo site https://www.blender.org/2-8/

Jeroen Bakker (jbakker) mentioned this in T64953: Cryptomatte - File Output node is messing up the multilayer exr (metadata), so blender cryptomattes cannot be read properly in external compositors.May 21 2019, 7:06 PM
Jeroen Bakker (jbakker) added a comment.May 24 2019, 9:41 AM

Seems like a color pipeline issue. The matte contains the 'lines' but they are not visible as it is stored in a value buffer (RAW buffer). When connecting a value directly to a color socket the data used as a linear color when displayed the display transform will be put on top. When exporting to PNG the colors are converted to sRGB.


When storing the matte in the Alpha channel of the color it will not be converted and you will see the right information.

I am not able to reproduce the issue you describe. (I was some time ago). Can you check if this is still failing.

Jeroen Bakker (jbakker) lowered the priority of this task from 50 to 30.May 24 2019, 9:42 AM
afaenger (afaenger) added a comment.May 27 2019, 8:30 AM

Tested again with blender-2.80-d525c76003b3-win64 (May 27th) and followed the steps as described above. The issue is still there and the png file written in 4) contains the unexpected lines; the viewer never shows the lines.

With the "set alpha" workaround, the lines don't appear.

Jeroen Bakker (jbakker) added a comment.May 28 2019, 2:42 PM

Lemme try again.
Result step 1:

Result after step 4:

Both results are identical. The exposure of the file you are using is set to 5.5 what destroys the visual presentation of the data. When set to normal values you will also see the stripes in the viewport.

Is this the same result you get?

afaenger (afaenger) added a comment.May 29 2019, 8:59 AM

Yes, I get the same result in the viewer now if I change the settings to
Scene->Color Management: View Transform=Standard (instead of Filmic), Exposure=0.0 (instead of 5.5)

The stripes are not visible in the viewport if exposure is above ca. 0.7-0.8.

I think I understand now why the stripes are visible/invisible. But why is the behavior not consistent with the steps I described above? Shouldn't be the rendering results always be the same, no matter if I restart the application or add or remove some file outputs?

Jeroen Bakker (jbakker) added a comment.May 29 2019, 9:15 AM

I am not able to detect any inconsistencies between step 1 and 4. You still are?

afaenger (afaenger) added a comment.May 29 2019, 9:42 AM

Yes, e.g. when exposure is set to 1. The viewport then contains no stripes, the png output contains them sometimes. I think the rendering results should always be the same in order to correctly work with the scene. Basically when using higher exposure values, then the issue appears.

Brecht Van Lommel (brecht) raised the priority of this task from 30 to 90.Jun 7 2019, 11:23 AM
Jeroen Bakker (jbakker) changed the task status from Unknown Status to Unknown Status.Jun 7 2019, 3:07 PM

We are aware of the limitations of blender single channel image pipeline. We intend to solve this in the future were we give users more control on the color spaces.

For now we will close this task as it is not a bug.