USDZExporter: Modulate diffuse map

[kolodi]

Related issue: #21871

A material can have a color different from white. Color is rendered on top of existing map (diffuse).
Initially I was thinking to use the bias input for Texture Reader, but unfortunately it does not worl, at least not in QuickLook.

Current solutions is more like a workaround and may be revisited some day.

[mrdoob]

Thanks!

[mrdoob]

Ended up refactoring the code quite a bit: afb032b

[mrdoob]

This commit may shows better the implementation: 2ceaad9

[mrdoob]

Also, turns out I had broken USDZExporter here: 14fab09
Took me quite a few hours to figure out the fix: a09a704?w=1

[kolodi]

Very good. Next step - fix broken ao map ;-)

[kolodi]

See my other comments in 2ceaad9

[mrdoob]

Very good. Next step - fix broken ao map ;-)

Yeah. Not sure how to fix that. As far as I understand USDZ only supports 1 uv channel.

[mrdoob]

By the way, there are a lot of tricks here:

https://github.com/google/usd_from_gltf#emulated-functionality-for-ar-quick-look

[kolodi]

By the way, there are a lot of tricks here:

https://github.com/google/usd_from_gltf#emulated-functionality-for-ar-quick-look

Quite dated. For example, they ended up scaling textures to "simulate" tiling...