Mirror.js

/**
 * @author Slayvin / http://slayvin.net
 */

THREE.Mirror = function ( renderer, camera, options ) {

	THREE.Object3D.call( this );

	this.name = 'mirror_' + this.id;

	options = options || {};

	this.matrixNeedsUpdate = true;

	var width = options.textureWidth !== undefined ? options.textureWidth : 512;
	var height = options.textureHeight !== undefined ? options.textureHeight : 512;

	this.clipBias = options.clipBias !== undefined ? options.clipBias : 0.0;

	var mirrorColor = options.color !== undefined ? new THREE.Color( options.color ) : new THREE.Color( 0x7F7F7F );

	this.renderer = renderer;
	this.mirrorPlane = new THREE.Plane();
	this.normal = new THREE.Vector3( 0, 0, 1 );
	this.mirrorWorldPosition = new THREE.Vector3();
	this.cameraWorldPosition = new THREE.Vector3();
	this.rotationMatrix = new THREE.Matrix4();
	this.lookAtPosition = new THREE.Vector3( 0, 0, - 1 );
	this.clipPlane = new THREE.Vector4();

	if ( camera instanceof THREE.PerspectiveCamera ) {

		this.camera = camera;

	} else {

		this.camera = new THREE.PerspectiveCamera();
		console.log( this.name + ': camera is not a Perspective Camera!' );

	}

	this.textureMatrix = new THREE.Matrix4();

	this.mirrorCamera = this.camera.clone();
	this.mirrorCamera.matrixAutoUpdate = true;

	var parameters = { minFilter: THREE.LinearFilter, magFilter: THREE.LinearFilter, format: THREE.RGBFormat, stencilBuffer: false };

	this.renderTarget = new THREE.WebGLRenderTarget( width, height, parameters );
	this.renderTarget2 = new THREE.WebGLRenderTarget( width, height, parameters );

	var mirrorShader = {

		uniforms: {
			mirrorColor: { value: new THREE.Color( 0x7F7F7F ) },
			mirrorSampler: { value: null },
			textureMatrix: { value: new THREE.Matrix4() }
		},

		vertexShader: [
			'uniform mat4 textureMatrix;',
			'varying vec4 mirrorCoord;',

			'void main() {',

			'	vec4 mvPosition = modelViewMatrix * vec4( position, 1.0 );',
			'	vec4 worldPosition = modelMatrix * vec4( position, 1.0 );',
			'	mirrorCoord = textureMatrix * worldPosition;',

			'	gl_Position = projectionMatrix * mvPosition;',

			'}'
		].join( '\n' ),

		fragmentShader: [
			'uniform vec3 mirrorColor;',
			'uniform sampler2D mirrorSampler;',
			'varying vec4 mirrorCoord;',

			'float blendOverlay(float base, float blend) {',
			'	return( base < 0.5 ? ( 2.0 * base * blend ) : (1.0 - 2.0 * ( 1.0 - base ) * ( 1.0 - blend ) ) );',
			'}',

			'void main() {',
			'	vec4 color = texture2DProj(mirrorSampler, mirrorCoord);',
			'	color = vec4(blendOverlay(mirrorColor.r, color.r), blendOverlay(mirrorColor.g, color.g), blendOverlay(mirrorColor.b, color.b), 1.0);',
			'	gl_FragColor = color;',
			'}'
		].join( '\n' )

	};

	var mirrorUniforms = THREE.UniformsUtils.clone( mirrorShader.uniforms );

	this.material = new THREE.ShaderMaterial( {

		fragmentShader: mirrorShader.fragmentShader,
		vertexShader: mirrorShader.vertexShader,
		uniforms: mirrorUniforms

	} );

	this.material.uniforms.mirrorSampler.value = this.renderTarget.texture;
	this.material.uniforms.mirrorColor.value = mirrorColor;
	this.material.uniforms.textureMatrix.value = this.textureMatrix;

	if ( ! THREE.Math.isPowerOfTwo( width ) || ! THREE.Math.isPowerOfTwo( height ) ) {

		this.renderTarget.texture.generateMipmaps = false;
		this.renderTarget2.texture.generateMipmaps = false;

	}

	this.updateTextureMatrix();
	this.render();

};

THREE.Mirror.prototype = Object.create( THREE.Object3D.prototype );

Object.assign( THREE.Mirror.prototype, {

	constructor: THREE.Mirror,

	renderWithMirror: function ( otherMirror ) {

		// update the mirror matrix to mirror the current view
		this.updateTextureMatrix();
		this.matrixNeedsUpdate = false;

		// set the camera of the other mirror so the mirrored view is the reference view
		var tempCamera = otherMirror.camera;
		otherMirror.camera = this.mirrorCamera;

		// render the other mirror in temp texture
		otherMirror.renderTemp();
		otherMirror.material.uniforms.mirrorSampler.value = otherMirror.renderTarget2.texture;

		// render the current mirror
		this.render();
		this.matrixNeedsUpdate = true;

		// restore material and camera of other mirror
		otherMirror.material.uniforms.mirrorSampler.value = otherMirror.renderTarget.texture;
		otherMirror.camera = tempCamera;

		// restore texture matrix of other mirror
		otherMirror.updateTextureMatrix();

	},

	updateTextureMatrix: function () {

		this.updateMatrixWorld();
		this.camera.updateMatrixWorld();

		this.mirrorWorldPosition.setFromMatrixPosition( this.matrixWorld );
		this.cameraWorldPosition.setFromMatrixPosition( this.camera.matrixWorld );

		this.rotationMatrix.extractRotation( this.matrixWorld );

		this.normal.set( 0, 0, 1 );
		this.normal.applyMatrix4( this.rotationMatrix );

		var view = this.mirrorWorldPosition.clone().sub( this.cameraWorldPosition );
		view.reflect( this.normal ).negate();
		view.add( this.mirrorWorldPosition );

		this.rotationMatrix.extractRotation( this.camera.matrixWorld );

		this.lookAtPosition.set( 0, 0, - 1 );
		this.lookAtPosition.applyMatrix4( this.rotationMatrix );
		this.lookAtPosition.add( this.cameraWorldPosition );

		var target = this.mirrorWorldPosition.clone().sub( this.lookAtPosition );
		target.reflect( this.normal ).negate();
		target.add( this.mirrorWorldPosition );

		this.up.set( 0, - 1, 0 );
		this.up.applyMatrix4( this.rotationMatrix );
		this.up.reflect( this.normal ).negate();

		this.mirrorCamera.position.copy( view );
		this.mirrorCamera.up = this.up;
		this.mirrorCamera.lookAt( target );

		this.mirrorCamera.updateProjectionMatrix();
		this.mirrorCamera.updateMatrixWorld();
		this.mirrorCamera.matrixWorldInverse.getInverse( this.mirrorCamera.matrixWorld );

		// Update the texture matrix
		this.textureMatrix.set(
			0.5, 0.0, 0.0, 0.5,
			0.0, 0.5, 0.0, 0.5,
			0.0, 0.0, 0.5, 0.5,
			0.0, 0.0, 0.0, 1.0
		);
		this.textureMatrix.multiply( this.mirrorCamera.projectionMatrix );
		this.textureMatrix.multiply( this.mirrorCamera.matrixWorldInverse );

		// Now update projection matrix with new clip plane, implementing code from: http://www.terathon.com/code/oblique.html
		// Paper explaining this technique: http://www.terathon.com/lengyel/Lengyel-Oblique.pdf
		this.mirrorPlane.setFromNormalAndCoplanarPoint( this.normal, this.mirrorWorldPosition );
		this.mirrorPlane.applyMatrix4( this.mirrorCamera.matrixWorldInverse );

		this.clipPlane.set( this.mirrorPlane.normal.x, this.mirrorPlane.normal.y, this.mirrorPlane.normal.z, this.mirrorPlane.constant );

		var q = new THREE.Vector4();
		var projectionMatrix = this.mirrorCamera.projectionMatrix;

		q.x = ( Math.sign( this.clipPlane.x ) + projectionMatrix.elements[ 8 ] ) / projectionMatrix.elements[ 0 ];
		q.y = ( Math.sign( this.clipPlane.y ) + projectionMatrix.elements[ 9 ] ) / projectionMatrix.elements[ 5 ];
		q.z = - 1.0;
		q.w = ( 1.0 + projectionMatrix.elements[ 10 ] ) / projectionMatrix.elements[ 14 ];

		// Calculate the scaled plane vector
		var c = new THREE.Vector4();
		c = this.clipPlane.multiplyScalar( 2.0 / this.clipPlane.dot( q ) );

		// Replacing the third row of the projection matrix
		projectionMatrix.elements[ 2 ] = c.x;
		projectionMatrix.elements[ 6 ] = c.y;
		projectionMatrix.elements[ 10 ] = c.z + 1.0 - this.clipBias;
		projectionMatrix.elements[ 14 ] = c.w;

	},

	render: function () {

		if ( this.matrixNeedsUpdate ) this.updateTextureMatrix();

		this.matrixNeedsUpdate = true;

		// Render the mirrored view of the current scene into the target texture
		var scene = this;

		while ( scene.parent !== null ) {

			scene = scene.parent;

		}

		if ( scene !== undefined && scene instanceof THREE.Scene ) {

			// We can't render ourself to ourself
			var visible = this.material.visible;
			this.material.visible = false;

			this.renderer.render( scene, this.mirrorCamera, this.renderTarget, true );

			this.material.visible = visible;

		}

	},

	renderTemp: function () {

		if ( this.matrixNeedsUpdate ) this.updateTextureMatrix();

		this.matrixNeedsUpdate = true;

		// Render the mirrored view of the current scene into the target texture
		var scene = this;

		while ( scene.parent !== null ) {

			scene = scene.parent;

		}

		if ( scene !== undefined && scene instanceof THREE.Scene ) {

			this.renderer.render( scene, this.mirrorCamera, this.renderTarget2, true );

		}

	}

} );