three.js/examples/js/postprocessing/ClearPass.js

( function () {

	var ClearPass = function ( clearColor, clearAlpha ) {

		THREE.Pass.call( this );
		this.needsSwap = false;
		this.clearColor = clearColor !== undefined ? clearColor : 0x000000;
		this.clearAlpha = clearAlpha !== undefined ? clearAlpha : 0;
		this._oldClearColor = new THREE.Color();

	};

	ClearPass.prototype = Object.assign( Object.create( THREE.Pass.prototype ), {
		constructor: ClearPass,
		render: function ( renderer, writeBuffer, readBuffer
			/*, deltaTime, maskActive */
		) {

			var oldClearAlpha;

			if ( this.clearColor ) {

				renderer.getClearColor( this._oldClearColor );
				oldClearAlpha = renderer.getClearAlpha();
				renderer.setClearColor( this.clearColor, this.clearAlpha );

			}

			renderer.setRenderTarget( this.renderToScreen ? null : readBuffer );
			renderer.clear();

			if ( this.clearColor ) {

				renderer.setClearColor( this._oldClearColor, oldClearAlpha );

			}

		}
	} );

	THREE.ClearPass = ClearPass;

} )();