constructor( uvNode = screenUV, levelNode = null ) {

		if ( sharedDepthbuffer === null ) {

			sharedDepthbuffer = new DepthTexture();

		}

		super( uvNode, levelNode, sharedDepthbuffer );

	}
Constructs a new viewport depth texture node.

@param {Node} [uvNode=screenUV] - The uv node.
@param {?Node} [levelNode=null] - The level node.