renderShadow( frame ) {

		const { shadow, shadowMap, light } = this;
		const { renderer, scene } = frame;

		shadow.updateMatrices( light );

		shadowMap.setSize( shadow.mapSize.width, shadow.mapSize.height, shadowMap.depth );

		renderer.render( scene, shadow.camera );

	}
Renders the shadow. The logic of this function could be included
into {@link ShadowNode#updateShadow} however more specialized shadow
nodes might require a custom shadow map rendering. By having a
dedicated method, it's easier to overwrite the default behavior.

@param {NodeFrame} frame - A reference to the current node frame.