Additional UV sets being removed with --transform, no option to make sure these are preserved

[Prungus]

When processing gltf or glb models that contain meshes with multiple UV sets, they are always removed without any way to ensure they stay. I have tested all flags with transform and there does not seem to be a way to keep multiple UV sets on the meshes. This is especially burdensome as Three.js has included proper support for multiple UV sets via texture channels as of r153

[donmccurdy]

The keepAttributes: false option passed to glTF Transform here is responsible for removing unused UVs:

gltfjsx/src/utils/transform.js

Line 68 in de1d1c2

prune({ keepAttributes: false, keepLeaves: false }),

As you note, gltfjsx doesn't expose an option to override that today. One workaround would be to pre-process the file with glTF Transform first, and skip --transform.

npx @gltf-transform/cli optimize input.glb output.glb --compress meshopt --texture-compress webp --texture-resize 2048

glTF Transform is configurable, and this is not exactly the same set of optimizations as gltfjsx has chosen, but you can try different options with the CLI to see what you prefer.

npx @gltf-transform/cli --help
npx @gltf-transform/cli optimize --help

[hichemfantar]

I'm having the same issue with normals being stripped from attributes.
we really need a way to override this behavior

@donmccurdy do you mind adding a flag to configure keepAttributes?

related issue #278

[donmccurdy]

@hichemfantar The flag is now exposed in the glTF Transform CLI to enable/disable keepAttributes, and could be changed for gltfjsx here if you'd like to make a pull request:

gltfjsx/src/utils/transform.js

Line 74 in 8da0e26

prune({ keepAttributes: false, keepLeaves: false }),