constructor( shader, textureID = 'tDiffuse' ) {

		super();

		/**
		 * The name of the texture uniform that should sample the read buffer.
		 *
		 * @type {string}
		 * @default 'tDiffuse'
		 */
		this.textureID = textureID;

		/**
		 * The pass uniforms.
		 *
		 * @type {?Object}
		 */
		this.uniforms = null;

		/**
		 * The pass material.
		 *
		 * @type {?ShaderMaterial}
		 */
		this.material = null;

		if ( shader instanceof ShaderMaterial ) {

			this.uniforms = shader.uniforms;

			this.material = shader;

		} else if ( shader ) {

			this.uniforms = UniformsUtils.clone( shader.uniforms );

			this.material = new ShaderMaterial( {

				name: ( shader.name !== undefined ) ? shader.name : 'unspecified',
				defines: Object.assign( {}, shader.defines ),
				uniforms: this.uniforms,
				vertexShader: shader.vertexShader,
				fragmentShader: shader.fragmentShader

			} );

		}

		// internals

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

	}
Constructs a new shader pass.

@param {Object|ShaderMaterial} [shader] - A shader object holding vertex and fragment shader as well as
defines and uniforms. It's also valid to pass a custom shader material.
@param {string} [textureID='tDiffuse'] - The name of the texture uniform that should sample
the read buffer.