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

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.clearDepth = false;
	this.needsSwap = false;
	this._oldClearColor = new THREE.Color();

};

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

	constructor: THREE.RenderPass,

	render: function ( renderer, writeBuffer, readBuffer /*, deltaTime, maskActive */ ) {

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

		var oldClearAlpha, oldOverrideMaterial;

		if ( this.overrideMaterial !== undefined ) {

			oldOverrideMaterial = this.scene.overrideMaterial;

			this.scene.overrideMaterial = this.overrideMaterial;

		}

		if ( this.clearColor ) {

			renderer.getClearColor( this._oldClearColor );
			oldClearAlpha = renderer.getClearAlpha();

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

		}

		if ( this.clearDepth ) {

			renderer.clearDepth();

		}

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

		// TODO: Avoid using autoClear properties, see https://github.com/mrdoob/three.js/pull/15571#issuecomment-465669600
		if ( this.clear ) renderer.clear( renderer.autoClearColor, renderer.autoClearDepth, renderer.autoClearStencil );
		renderer.render( this.scene, this.camera );

		if ( this.clearColor ) {

			renderer.setClearColor( this._oldClearColor, oldClearAlpha );

		}

		if ( this.overrideMaterial !== undefined ) {

			this.scene.overrideMaterial = oldOverrideMaterial;

		}

		renderer.autoClear = oldAutoClear;

	}

} );