MaterialX: Add normal, tangent, texcoord, geomcolor, position space support

[hybridherbst]

Description

Adds support for geometry attributes and (partial) parsing of geometry attribute space as described in the title.

There are two // TODO comments in the code:

• not sure how to get the texcoord index from the child node
• note sure if/how nodes should support multiple color attributes; it's not supported in MeshPhysicalMaterial right now.

cc @sunag

This contribution is funded by Needle

[sunag]

note sure if/how nodes should support multiple color attributes; it's not supported in MeshPhysicalMaterial right now.

It would be compatible in any case, if we proceed it would be interesting to support index as we did in UVNode.

[hybridherbst]

Thanks! Could you point me in the right direction for getting the UV index so I can remove the comment?
I think color index can be deferred for later (I can keep the comment).

[sunag]

Could you point me in the right direction for getting the UV index so I can remove the comment?

I think that getChildByName() can solve this issue.

if ( element === 'texcoord' ) {

	const index = this.getChildByName( 'index' );
	const indexValue = parseInt( index.value );

	node = uv( indexValue );

} 

[sunag]

I think color index can be deferred for later (I can keep the comment).

It seems positive to me to do this implementation. I added something like.

class VertexColorNode extends AttributeNode {

	constructor( index = 0 ) {

		super( null, 'vec4' );

		this.isVertexColorNode = true;

		this.index = index;

	}

	getAttributeName( /*builder*/ ) {

		const index = this.index;

		return 'color' + ( index > 0 ? index : '' );

	}

	...

}

[hybridherbst]

OK, added both. I unfortunately don't have a file at hand to test multi-UV and also none for testing multi-color (seems Blender only exports the first color channel).