constructor( light = null ) {

		super( light );

		/**
		 * Uniform node representing the light's position.
		 *
		 * @type {UniformNode<vec3>}
		 */
		this.lightPositionNode = lightPosition( light );

		/**
		 * A node representing the light's direction.
		 *
		 * @type {Node<vec3>}
		 */
		this.lightDirectionNode = this.lightPositionNode.normalize();

		/**
		 * Uniform node representing the light's ground color.
		 *
		 * @type {UniformNode<vec3>}
		 */
		this.groundColorNode = uniform( new Color() ).setGroup( renderGroup );

	}
Constructs a new hemisphere light node.

@param {?HemisphereLight} [light=null] - The hemisphere light source.