three.js/examples/js/effects/ParallaxBarrierEffect.js

( function () {

	var ParallaxBarrierEffect = function ( renderer ) {

		var _camera = new THREE.OrthographicCamera( - 1, 1, 1, - 1, 0, 1 );

		var _scene = new THREE.Scene();

		var _stereo = new THREE.StereoCamera();

		var _params = {
			minFilter: THREE.LinearFilter,
			magFilter: THREE.NearestFilter,
			format: THREE.RGBAFormat
		};

		var _renderTargetL = new THREE.WebGLRenderTarget( 512, 512, _params );

		var _renderTargetR = new THREE.WebGLRenderTarget( 512, 512, _params );

		var _material = new THREE.ShaderMaterial( {
			uniforms: {
				'mapLeft': {
					value: _renderTargetL.texture
				},
				'mapRight': {
					value: _renderTargetR.texture
				}
			},
			vertexShader: [ 'varying vec2 vUv;', 'void main() {', '	vUv = vec2( uv.x, uv.y );', '	gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );', '}' ].join( '\n' ),
			fragmentShader: [ 'uniform sampler2D mapLeft;', 'uniform sampler2D mapRight;', 'varying vec2 vUv;', 'void main() {', '	vec2 uv = vUv;', '	if ( ( mod( gl_FragCoord.y, 2.0 ) ) > 1.00 ) {', '		gl_FragColor = texture2D( mapLeft, uv );', '	} else {', '		gl_FragColor = texture2D( mapRight, uv );', '	}', '}' ].join( '\n' )
		} );

		var mesh = new THREE.Mesh( new THREE.PlaneGeometry( 2, 2 ), _material );

		_scene.add( mesh );

		this.setSize = function ( width, height ) {

			renderer.setSize( width, height );
			var pixelRatio = renderer.getPixelRatio();

			_renderTargetL.setSize( width * pixelRatio, height * pixelRatio );

			_renderTargetR.setSize( width * pixelRatio, height * pixelRatio );

		};

		this.render = function ( scene, camera ) {

			scene.updateMatrixWorld();
			if ( camera.parent === null ) camera.updateMatrixWorld();

			_stereo.update( camera );

			renderer.setRenderTarget( _renderTargetL );
			renderer.clear();
			renderer.render( scene, _stereo.cameraL );
			renderer.setRenderTarget( _renderTargetR );
			renderer.clear();
			renderer.render( scene, _stereo.cameraR );
			renderer.setRenderTarget( null );
			renderer.render( _scene, _camera );

		};

	};

	THREE.ParallaxBarrierEffect = ParallaxBarrierEffect;

} )();