setupLightMap( builder ) {

		let node = null;

		if ( builder.material.lightMap ) {

			node = new BasicLightMapNode( materialLightMap );

		}

		return node;

	}
This method must be overwritten since light maps are evaluated
with a special scaling factor for basic materials.

@param {NodeBuilder} builder - The current node builder.
@return {?BasicLightMapNode<vec3>} The light map node.