T60890: 2.8 GLTF/GLB Vertex Colors incorrect

[julienduroure]

On blender issue tracker: https://developer.blender.org/T60890

I asked some example files

[julienduroure]

Linked to #127 ?

[julienduroure]

The user added a test file and some details on blender issue tracker

[donmccurdy]

Posted an update on https://developer.blender.org/T60890 – I think the importer may need to convert, similarly to this PR: https://github.com/KhronosGroup/glTF-Blender-Exporter/pull/209/files. I can't reproduce an issue in the exporter, but only tested 2.80 so far. It's also possible that Godot is not handling vertex colors quite correctly; we should encourage users to compare at least one of the online viewers as well.

[donmccurdy]

colorTest.gltf.zip

[julienduroure]

@donmccurdy Fixed it in branch import_vertexcolor_linear2sRGB

Can you please test it on your side? 4 eyes are better than 2 for color issues :)

[capnm]

I'm only looking at the for import-export-import-... increased computing effort and precision lost.

I wonder if glTF should not support a proper color management as usual in the professional printing industry (ie ICC profiles)?

[donmccurdy]

@julienduroure this looks very, very close. On a roundtrip import/export the color becomes slightly darker, though – I've left a comment with what I think is the cause 08987ef.

I wonder if glTF should not support a proper color management as usual in the professional printing industry (ie ICC profiles)?

glTF is deliberately specific about how its colors must be managed, and exporters must convert data to that. glTF does not allow arbitrary color profiles to be used inside the file – while that makes sense when the final output is a printed product, the data passed to a realtime engine needs to match what engines support.

[julienduroure]

You're right, I miss-read the formula. Will fix it asap

[julienduroure]

@donmccurdy I just pushed a fix :)

[donmccurdy]

@julienduroure the fix looks correct now, thanks! roundtrip import/export is giving the same vertex colors for me. :)