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 : 1;

	this.oldClearColor = new THREE.Color();
	this.oldClearAlpha = 1;

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

};

THREE.RenderPass.prototype = Object.create( THREE.Pass.prototype );

Object.assign( THREE.RenderPass.prototype, {

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

		this.scene.overrideMaterial = this.overrideMaterial;

		if ( this.clearColor ) {

			this.oldClearColor.copy( renderer.getClearColor() );
			this.oldClearAlpha = renderer.getClearAlpha();

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

		}

		renderer.render( this.scene, this.camera, readBuffer, this.clear );

		if ( this.clearColor ) {

			renderer.setClearColor( this.oldClearColor, this.oldClearAlpha );

		}

		this.scene.overrideMaterial = null;

	}

} );