GLTFLoader support KHR_texture_procedurals

[DennisSmolek]

Description

GLTF is gearing up to be the final mile delivery system for 3D platforms. One of the key goals expressed is better interoperability between GLTF and OpenUSD. One of the primary ways to do that is supporting MaterialX.

To do that, GLTF first wants to support procedural materials (including MaterialX) through a JSON defined node graph system for materials: https://github.com/KhronosGroup/glTF/tree/KHR_texture_procedurals/extensions/2.0/Khronos/KHR_texture_procedurals

From there, different systems/versions of procedural materials can be loaded, (however this primarily seems to be aimed at specifying versions of MaterialX, though I could see it supporting other systems)

Outline of GLTF/MaterialX 1.39

Link to the PR

At Siggraph 2024 Asia this was highlighted as done/near done and also one of the key goals within gltf. This is 100% happening and I think threejs should be a leader of it's implementation or at a minimum prepared for it.

This issue is first to mark the item within threeJS and hopefully could act as a holder of other issues related to it. I searched (a little) and found some issues mentioning parts of this, but it's hard to understand what is happening without following all open issues.

Solution

The first task would be parsing the GLTF Json into a ThreeJS material using TSL and the correct material type.

I'm not sure if the GLTF system can tag in a way if a material would need to be a basic, standard, or Physical material, however it could be built as a standard material and then rebuilt as a basic if it only has the basic inputs or a physical if it has the more complex ones. (implementation discussion)

I know there is currently a materialX loader, however, that is parsing the XML matx files and not this converted JSON. A new parser would have to be put together but could use that as a starting point.

I am willing to start working on this in my desire to do more for things within gltf, however I didn't want to start if @sunag already had something in the works

Alternatives

Additional context

There are a million links to MaterialX stuff. But MaterialXLearn might be the easiest to link to all the other resources, see graphs, editors, etc.