setupDiffuseColor() {

		const opacityNode = this.opacityNode ? float( this.opacityNode ) : materialOpacity;

		// By convention, a normal packed to RGB is in sRGB color space. Convert it to working color space.

		diffuseColor.assign( colorSpaceToWorking( vec4( directionToColor( transformedNormalView ), opacityNode ), SRGBColorSpace ) );

	}
Overwrites the default implementation by computing the diffuse color
based on the normal data.