constructor( uvNode = screenUV, levelNode = null, framebufferTexture = null ) {

		if ( framebufferTexture === null ) {

			framebufferTexture = new FramebufferTexture();
			framebufferTexture.minFilter = LinearMipmapLinearFilter;

		}

		super( framebufferTexture, uvNode, levelNode );

		/**
		 * Whether to generate mipmaps or not.
		 *
		 * @type {boolean}
		 * @default false
		 */
		this.generateMipmaps = false;

		/**
		 * This flag can be used for type testing.
		 *
		 * @type {boolean}
		 * @readonly
		 * @default true
		 */
		this.isOutputTextureNode = true;

		/**
		 * The `updateBeforeType` is set to `NodeUpdateType.FRAME` since the node renders the
		 * scene once per frame in its {@link ViewportTextureNode#updateBefore} method.
		 *
		 * @type {string}
		 * @default 'frame'
		 */
		this.updateBeforeType = NodeUpdateType.FRAME;

	}
Constructs a new viewport texture node.

@param {Node} [uvNode=screenUV] - The uv node.
@param {?Node} [levelNode=null] - The level node.
@param {?Texture} [framebufferTexture=null] - A framebuffer texture holding the viewport data. If not provided, a framebuffer texture is created automatically.