WebGPU NodeMaterial: How do I sample material textures in UVs other than model UV?

Questions
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1

I’m currently trying to create a custom Material / LightingModel using the NodeMaterial implementation (namely, MToon for three-vrm.)

I have bumped into an issue that, when I create MaterialReferenceNode in texture type, I cannot sample the referenced texture with irregular UVs (specifically, I want to sample the texture in MatCap UV.)
Do you have any idea to achieve this?

2

@sunag Sorry for the ping but you are probably the only person able to help me (not in a rush, don’t worry)

3

LightingModel is not designed to replace UV, but this could work by extending some NodeMaterial class.

class ToonNodeMaterial extends MeshBasicNodeMaterial {

	...
	
	setup( builder ) {
	
		builder.setContext( { ...builder.context, 
			getUVNode: ( /*reqNode*/ ) => {
				
				return uv(); // return a custom uv
			
			}
		} );	
	
		return super.setup( builder );
	
	}

}

In this case, the texture() that does not have UV defined will be replaced by the one defined in the context.

@sunag Sorry for the ping but you are probably the only person able to help me (not in a rush, don’t worry)

Feel free to ping me if you need to.

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4

Thank you for the reply!

Yes, I’m already extending NodeMaterial and LightingModel and the material already uses the default uv for ordinary map textures like map or emissiveMap.
AND I need another uv for the matcap use. Looking at the codes you’ve mentioned,

I noticed that TextureNode has a node inlet .uvNode, and MaterialReferenceNode has a property .node which is an actual TextureNode under the hood.
If I change the .uvNode like this it samples using matcap uv.
Is this an intended way to use this?

export const refMatcapTexture = Nodes.materialReference('matcapTexture', 'texture');
refMatcapTexture.node.uvNode = Nodes.matcapUV.mul(1.0, -1.0).add(0.0, 1.0);
5

You can try something like this too.

export const refMatcapTexture = materialReference( 'matcapTexture', 'texture' ).context( {
	getUVNode: ( /*reqNode*/ ) => {
				
		return matcapUV.mul( vec2( 1.0, -1.0 ) ).add( vec2( 0.0, 1.0 ) );
			
	}
} );

This manipulation can also be controlled within setup().

1 Like
6

Ahhh, ContextNode exists, interesting.
Is the builder.context an object that we can put any stuff we need to use to build nodes?

7

Each Node can use builder.context differently, this helps to apply settings that cannot be passed at declaration time, creating a layer in which the Node can retrieve the ideal settings for that flow.

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8

for record:

r159 will change the context.getUVNode to context.getUV.

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