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Maniphest T98267

Python API issue: attributes.active_color vs vertex_colors.active
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Description

Blender Version
Broken: version: 3.3.0 Alpha, branch: master, commit date: 2022-05-19 10:04, hash: rB4fc96e5000ce
Worked: n/a

Short description of error
The values I get from vertex_colors.active is different than from attributes.active_color.

Exact steps for others to reproduce the error
Open and run the Python script there (see the results in the console):

attribute_bug.blend104 KBDownload

Note: This mesh above is part of the cloth brush icon from the icons_geom.blend.

But I can also reproduce it with from scratch by painting a plane with some non-white colors like this:

Revisions and Commits

rB Blender
D14989rB469ee7ff1529 Python API: add mathutils.Color functions to convert color spaces

Related Objects

Event Timeline

Dalai Felinto (dfelinto) changed the task status from Needs Triage to Confirmed.May 19 2022, 7:32 PM
Dalai Felinto (dfelinto) created this task.
Dalai Felinto (dfelinto) added projects: Geometry Nodes, Nodes & Physics, Python API.
Dalai Felinto (dfelinto) edited subscribers, added: Hans Goudey (HooglyBoogly); removed: Dalai Felinto (dfelinto).

Setting status to confirmed, but not setting as a bug yet. Waiting for Hans to confirm it.

Dalai Felinto (dfelinto) mentioned this in D14988: Tool Icons: Support curve and objects with modifiers + color space fix.May 19 2022, 7:36 PM
Brecht Van Lommel (brecht) added a subscriber: Brecht Van Lommel (brecht).May 19 2022, 7:52 PM

This was an intentional design choice. For attributes I wanted to have all color values in the same linear color space in the API and UI, regardless if they are stored as byte or float. That way the values match in color pickers, spreadsheet, shader nodes, geometry nodes.

It's also just the general convention for any colors in scene data to be linear, with the old vertex colors as perhaps the last exception.

Dalai Felinto (dfelinto) added a comment.May 19 2022, 7:52 PM

I talked to @Brecht Van Lommel (brecht) and it seems that this is intentional. I think we should mention this in the release notes of whenever we introduced this (with an example of how to convert the values from one to the other?). I couldn't find it in any of the 3.x release notes so far.

Brecht Van Lommel (brecht) added a revision: D14989: Python API: add mathutils.Color functions to convert color spaces.May 19 2022, 9:25 PM
Brecht Van Lommel (brecht) added a comment.May 19 2022, 9:31 PM

I've updated the release notes now. In order to conveniently convert to/from sRGB we need some API functions, for which I added a patch.

Brecht Van Lommel (brecht) closed this task as Resolved by committing rB469ee7ff1529: Python API: add mathutils.Color functions to convert color spaces.May 23 2022, 3:37 PM
Brecht Van Lommel (brecht) claimed this task.
Brecht Van Lommel (brecht) added a commit: rB469ee7ff1529: Python API: add mathutils.Color functions to convert color spaces.