constructor( renderer, renderTarget ) {

		/**
		 * The renderer.
		 *
		 * @type {WebGLRenderer}
		 */
		this.renderer = renderer;

		this._pixelRatio = renderer.getPixelRatio();

		if ( renderTarget === undefined ) {

			const size = renderer.getSize( new Vector2() );
			this._width = size.width;
			this._height = size.height;

			renderTarget = new WebGLRenderTarget( this._width * this._pixelRatio, this._height * this._pixelRatio, { type: HalfFloatType } );
			renderTarget.texture.name = 'EffectComposer.rt1';

		} else {

			this._width = renderTarget.width;
			this._height = renderTarget.height;

		}

		this.renderTarget1 = renderTarget;
		this.renderTarget2 = renderTarget.clone();
		this.renderTarget2.texture.name = 'EffectComposer.rt2';

		/**
		 * A reference to the internal write buffer. Passes usually write
		 * their result into this buffer.
		 *
		 * @type {WebGLRenderTarget}
		 */
		this.writeBuffer = this.renderTarget1;

		/**
		 * A reference to the internal read buffer. Passes usually read
		 * the previous render result from this buffer.
		 *
		 * @type {WebGLRenderTarget}
		 */
		this.readBuffer = this.renderTarget2;

		/**
		 * Whether the final pass is rendered to the screen (default framebuffer) or not.
		 *
		 * @type {boolean}
		 * @default true
		 */
		this.renderToScreen = true;

		/**
		 * An array representing the (ordered) chain of post-processing passes.
		 *
		 * @type {Array<Pass>}
		 */
		this.passes = [];

		/**
		 * A copy pass used for internal swap operations.
		 *
		 * @private
		 * @type {ShaderPass}
		 */
		this.copyPass = new ShaderPass( CopyShader );
		this.copyPass.material.blending = NoBlending;

		/**
		 * The internal clock for managing time data.
		 *
		 * @private
		 * @type {Clock}
		 */
		this.clock = new Clock();

	}
Constructs a new effect composer.

@param {WebGLRenderer} renderer - The renderer.
@param {WebGLRenderTarget} [renderTarget] - This render target and a clone will
be used as the internal read and write buffers. If not given, the composer creates
the buffers automatically.