three.js/examples/js/postprocessing/RenderPass.js

/**
 * @author alteredq / http://alteredqualia.com/
 */

THREE.RenderPass = function ( scene, camera, overrideMaterial, clearColor, clearAlpha ) {

	THREE.Pass.call( this );

	this.scene = scene;
	this.camera = camera;

	this.overrideMaterial = overrideMaterial;

	this.clearColor = clearColor;
	this.clearAlpha = ( clearAlpha !== undefined ) ? clearAlpha : 0;

	this.clear = true;
	this.needsSwap = false;

};

THREE.RenderPass.prototype = Object.assign( Object.create( THREE.Pass.prototype ), {

	constructor: THREE.RenderPass,

	render: function ( renderer, writeBuffer, readBuffer, delta, maskActive ) {

		var oldAutoClear = renderer.autoClear;
		renderer.autoClear = false;

		this.scene.overrideMaterial = this.overrideMaterial;

		var oldClearColor, oldClearAlpha;

		if ( this.clearColor ) {

			oldClearColor = renderer.getClearColor().getHex();
			oldClearAlpha = renderer.getClearAlpha();

			renderer.setClearColor( this.clearColor, this.clearAlpha );

		}

		renderer.render( this.scene, this.camera, this.renderToScreen ? null : readBuffer, this.clear );

		if ( this.clearColor ) {

			renderer.setClearColor( oldClearColor, oldClearAlpha );

		}

		this.scene.overrideMaterial = null;
		renderer.autoClear = oldAutoClear;
	}

} );