constructor( scene, camera, clearColor = 0x000000, clearAlpha = 0 ) {

		super();

		/**
		 * The scene to render.
		 *
		 * @type {Scene}
		 */
		this.scene = scene;

		/**
		 * The camera.
		 *
		 * @type {Camera}
		 */
		this.camera = camera;

		/**
		 * The sample level. Specified as n, where the number of
		 * samples is 2^n, so sampleLevel = 4, is 2^4 samples, 16.
		 *
		 * @type {number}
		 * @default 4
		 */
		this.sampleLevel = 4;

		/**
		 * Whether the pass should be unbiased or not. This property has the most
		 * visible effect when rendering to a RGBA8 buffer because it mitigates
		 * rounding errors. By default RGBA16F is used.
		 *
		 * @type {boolean}
		 * @default true
		 */
		this.unbiased = true;

		/**
		 * Whether to use a stencil buffer or not. This property can't
		 * be changed after the first render.
		 *
		 * @type {boolean}
		 * @default false
		 */
		this.stencilBuffer = false;

		/**
		 * The clear color of the render pass.
		 *
		 * @type {?(number|Color|string)}
		 * @default 0x000000
		 */
		this.clearColor = clearColor;

		/**
		 * The clear alpha of the render pass.
		 *
		 * @type {?number}
		 * @default 0
		 */
		this.clearAlpha = clearAlpha;

		// internals

		this._sampleRenderTarget = null;

		this._oldClearColor = new Color();

		this._copyUniforms = UniformsUtils.clone( CopyShader.uniforms );

		this._copyMaterial = new ShaderMaterial(	{
			uniforms: this._copyUniforms,
			vertexShader: CopyShader.vertexShader,
			fragmentShader: CopyShader.fragmentShader,
			transparent: true,
			depthTest: false,
			depthWrite: false,
			premultipliedAlpha: true,
			blending: AdditiveBlending
		} );

		this._fsQuad = new FullScreenQuad( this._copyMaterial );

	}
Constructs a new SSAA render pass.

@param {Scene} scene - The scene to render.
@param {Camera} camera - The camera.
@param {?(number|Color|string)} [clearColor=0x000000] - The clear color of the render pass.
@param {?number} [clearAlpha=0] - The clear alpha of the render pass.