three.js/examples/js/postprocessing/EffectComposer.js

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

THREE.EffectComposer = function ( renderer, renderTarget ) {

	this.renderer = renderer;

	this.renderTarget1 = renderTarget;

	if ( this.renderTarget1 === undefined ) {

		var width = window.innerWidth || 1;
		var height = window.innerHeight || 1;

		this.renderTargetParameters = { minFilter: THREE.LinearFilter, magFilter: THREE.LinearFilter, format: THREE.RGBFormat, stencilBuffer: false };
		this.renderTarget1 = new THREE.WebGLRenderTarget( width, height, this.renderTargetParameters );

	}

	this.renderTarget2 = this.renderTarget1.clone();

	this.writeBuffer = this.renderTarget1;
	this.readBuffer = this.renderTarget2;

	this.passes = [];

	if ( THREE.BlitShader === undefined )
		console.error( "THREE.EffectComposer relies on THREE.BlitShader" );

	this.copyPass = new THREE.ShaderPass( THREE.BlitShader );

};

THREE.EffectComposer.prototype = {

	swapBuffers: function() {

		var tmp = this.readBuffer;
		this.readBuffer = this.writeBuffer;
		this.writeBuffer = tmp;

	},

	addPass: function ( pass ) {

		this.passes.push( pass );

	},

	render: function ( delta ) {

		this.writeBuffer = this.renderTarget1;
		this.readBuffer = this.renderTarget2;

		var maskActive = false;

		var pass, i, il = this.passes.length;

		for ( i = 0; i < il; i ++ ) {

			pass = this.passes[ i ];

			if ( !pass.enabled ) continue;

			pass.render( this.renderer, this.writeBuffer, this.readBuffer, delta, maskActive );

			if ( pass.needsSwap ) {

				if ( maskActive ) {

					var context = this.renderer.context;

					context.stencilFunc( context.NOTEQUAL, 1, 0xffffffff );

					this.copyPass.render( this.renderer, this.writeBuffer, this.readBuffer, delta );

					context.stencilFunc( context.EQUAL, 1, 0xffffffff );

				}

				this.swapBuffers();

			}

			if ( pass instanceof THREE.MaskPass ) {

				maskActive = true;

			} else if ( pass instanceof THREE.ClearMaskPass ) {

				maskActive = false;

			}

		}

	},

	reset: function ( renderTarget ) {

		this.renderTarget1 = renderTarget;

		if ( this.renderTarget1 === undefined ) {

			this.renderTarget1 = new THREE.WebGLRenderTarget( window.innerWidth, window.innerHeight, this.renderTargetParameters );

		}

		this.renderTarget2 = this.renderTarget1.clone();

		this.writeBuffer = this.renderTarget1;
		this.readBuffer = this.renderTarget2;

	}

};

// shared ortho camera

THREE.EffectComposer.camera = new THREE.OrthographicCamera( -1, 1, 1, -1, 0, 1 );

THREE.EffectComposer.quad = new THREE.Mesh( new THREE.PlaneGeometry( 2, 2 ), null );

THREE.EffectComposer.scene = new THREE.Scene();
THREE.EffectComposer.scene.add( THREE.EffectComposer.quad );