Use the vertex colors by default in gltf.

[fire]

Fixes #21087

[fire]

[akien-mga]

17:01 <Akien> reduz: ok with #41007 ?
17:11 <reduz> that makes the shader more complex if you are not using the vertex colors
17:11 <reduz> so no
17:12 <reduz> also I have seen many times models that have vertex colors but they are not used, so when you load them the model looks wrong
17:13 <reduz> so in general, its better to enable vertex color import only if you are meaning to use them
17:13 <Akien> Can this be set as default import preset for users that want it?
17:13 <Akien> I mean from the import dock
17:13 <reduz> Akien: you can already set it as a default import preset, what we never did is a way to edit the default import pressets in the project settings
17:14 <reduz> we should probably do that
17:14 <reduz> so you can only override them, not change them
17:14 <Akien> Yeah that would be nice also for setting pixel art presets, etc.

Closing as per the above, it's best to leave it up to users to set a default import preset for glTF that uses vertex colors if they know they'll benefit from it systematically.

[fire]

The GLTF spec says vertex colors need to be mixed with materials, so I don't know how to solve this.

[capnm]

17:12 also I have seen many times models that have vertex colors
but they are not used, so when you load them the model looks wrong

The model is then exported incorrectly, it shouldn't contain any vertex colors ...
you can then fix that in the material-settings manually.

[fire]

iFire> reduz: So for clarity is the decision still to not to have vertex colors default to mix with the material for glTF2? It's ok to say no, but being in decision limbo is worse.
10:35 AM
Juan Linietsky iFire: to be honest, gltf2 probably is ok
10:35 AM for collada and fbx i am less sure
10:36 AM
that's a good reason
10:36 AM
Juan Linietsky the problem is that we will need to detect this and turn it on in the material

[akien-mga]

Well I thought that there was an import option for this, but obviously I must have been mistaken. Not sure what @reduz was referring to then.

Let's reopen and assess further.

[fire]

reduz> Juan Linietsky iFire: probably but the commits are kind of a mess, needs to be rebased

Will rebase when I have a free moment.

[akien-mga]

Thanks!

[capnm]

3.2 PR: #41149

(Sorry for the spam here, github keeps referencing old rebased commits and and doesn't have a [Garbage Collection] button)

[akien-mga]

Cherry-picked for 3.2.4.