constructor( uvNode = screenUV, levelNode = null ) {

		if ( _sharedFramebuffer === null ) {

			_sharedFramebuffer = new FramebufferTexture();

		}

		super( uvNode, levelNode, _sharedFramebuffer );

	}
Constructs a new viewport shared texture node.

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