three.js/examples/js/effects/PeppersGhostEffect.js

( function () {

	/**
 * peppers ghost effect based on http://www.instructables.com/id/Reflective-Prism/?ALLSTEPS
 */

	class PeppersGhostEffect {

		constructor( renderer ) {

			const scope = this;
			scope.cameraDistance = 15;
			scope.reflectFromAbove = false;

			// Internals
			let _halfWidth, _width, _height;
			const _cameraF = new THREE.PerspectiveCamera(); //front
			const _cameraB = new THREE.PerspectiveCamera(); //back
			const _cameraL = new THREE.PerspectiveCamera(); //left
			const _cameraR = new THREE.PerspectiveCamera(); //right

			const _position = new THREE.Vector3();
			const _quaternion = new THREE.Quaternion();
			const _scale = new THREE.Vector3();

			// Initialization
			renderer.autoClear = false;
			this.setSize = function ( width, height ) {

				_halfWidth = width / 2;
				if ( width < height ) {

					_width = width / 3;
					_height = width / 3;

				} else {

					_width = height / 3;
					_height = height / 3;

				}

				renderer.setSize( width, height );

			};

			this.render = function ( scene, camera ) {

				if ( scene.matrixWorldAutoUpdate === true ) scene.updateMatrixWorld();
				if ( camera.parent === null && camera.matrixWorldAutoUpdate === true ) camera.updateMatrixWorld();
				camera.matrixWorld.decompose( _position, _quaternion, _scale );

				// front
				_cameraF.position.copy( _position );
				_cameraF.quaternion.copy( _quaternion );
				_cameraF.translateZ( scope.cameraDistance );
				_cameraF.lookAt( scene.position );

				// back
				_cameraB.position.copy( _position );
				_cameraB.quaternion.copy( _quaternion );
				_cameraB.translateZ( - scope.cameraDistance );
				_cameraB.lookAt( scene.position );
				_cameraB.rotation.z += 180 * ( Math.PI / 180 );

				// left
				_cameraL.position.copy( _position );
				_cameraL.quaternion.copy( _quaternion );
				_cameraL.translateX( - scope.cameraDistance );
				_cameraL.lookAt( scene.position );
				_cameraL.rotation.x += 90 * ( Math.PI / 180 );

				// right
				_cameraR.position.copy( _position );
				_cameraR.quaternion.copy( _quaternion );
				_cameraR.translateX( scope.cameraDistance );
				_cameraR.lookAt( scene.position );
				_cameraR.rotation.x += 90 * ( Math.PI / 180 );
				renderer.clear();
				renderer.setScissorTest( true );
				renderer.setScissor( _halfWidth - _width / 2, _height * 2, _width, _height );
				renderer.setViewport( _halfWidth - _width / 2, _height * 2, _width, _height );
				if ( scope.reflectFromAbove ) {

					renderer.render( scene, _cameraB );

				} else {

					renderer.render( scene, _cameraF );

				}

				renderer.setScissor( _halfWidth - _width / 2, 0, _width, _height );
				renderer.setViewport( _halfWidth - _width / 2, 0, _width, _height );
				if ( scope.reflectFromAbove ) {

					renderer.render( scene, _cameraF );

				} else {

					renderer.render( scene, _cameraB );

				}

				renderer.setScissor( _halfWidth - _width / 2 - _width, _height, _width, _height );
				renderer.setViewport( _halfWidth - _width / 2 - _width, _height, _width, _height );
				if ( scope.reflectFromAbove ) {

					renderer.render( scene, _cameraR );

				} else {

					renderer.render( scene, _cameraL );

				}

				renderer.setScissor( _halfWidth + _width / 2, _height, _width, _height );
				renderer.setViewport( _halfWidth + _width / 2, _height, _width, _height );
				if ( scope.reflectFromAbove ) {

					renderer.render( scene, _cameraL );

				} else {

					renderer.render( scene, _cameraR );

				}

				renderer.setScissorTest( false );

			};

		}

	}

	THREE.PeppersGhostEffect = PeppersGhostEffect;

} )();