Normal attributes are removed with --transform

[hichemfantar]

Need a way to override this behavior because three.js throws an error because it expects the normal attribute to be present

related mrdoob/three.js#29462

[donmccurdy]

Currently gltfjsx (via glTF Transform) will remove a normal attribute is if the geometry is either unlit (MeshBasicMaterial) or a point cloud. three.js does not in general require a normal attribute in these cases, but it sounds like you're hitting a problem with Decal geometry. That could be fixed upstream in three.js, but I think a PR here would be OK too.

If you'd like to disable that, it would be necessary to enable the keepAttributes flag here:

gltfjsx/src/utils/transform.js

Line 74 in 8da0e26

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

This change would also cause unused UVs and tangents to be kept, relevant to #235.