three.js/examples/jsm/effects/AnaglyphEffect.js

import {
	LinearFilter,
	Matrix3,
	Mesh,
	NearestFilter,
	OrthographicCamera,
	PlaneGeometry,
	RGBAFormat,
	Scene,
	ShaderMaterial,
	StereoCamera,
	WebGLRenderTarget
} from 'three';

class AnaglyphEffect {

	constructor( renderer, width = 512, height = 512 ) {

		// Dubois matrices from https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.7.6968&rep=rep1&type=pdf#page=4

		this.colorMatrixLeft = new Matrix3().fromArray( [
			0.456100, - 0.0400822, - 0.0152161,
			0.500484, - 0.0378246, - 0.0205971,
			0.176381, - 0.0157589, - 0.00546856
		] );

		this.colorMatrixRight = new Matrix3().fromArray( [
			- 0.0434706, 0.378476, - 0.0721527,
			- 0.0879388, 0.73364, - 0.112961,
			- 0.00155529, - 0.0184503, 1.2264
		] );

		const _camera = new OrthographicCamera( - 1, 1, 1, - 1, 0, 1 );

		const _scene = new Scene();

		const _stereo = new StereoCamera();

		const _params = { minFilter: LinearFilter, magFilter: NearestFilter, format: RGBAFormat };

		const _renderTargetL = new WebGLRenderTarget( width, height, _params );
		const _renderTargetR = new WebGLRenderTarget( width, height, _params );

		const _material = new ShaderMaterial( {

			uniforms: {

				'mapLeft': { value: _renderTargetL.texture },
				'mapRight': { value: _renderTargetR.texture },

				'colorMatrixLeft': { value: this.colorMatrixLeft },
				'colorMatrixRight': { value: this.colorMatrixRight }

			},

			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;',

				'uniform mat3 colorMatrixLeft;',
				'uniform mat3 colorMatrixRight;',

				'void main() {',

				'	vec2 uv = vUv;',

				'	vec4 colorL = texture2D( mapLeft, uv );',
				'	vec4 colorR = texture2D( mapRight, uv );',

				'	vec3 color = clamp(',
				'			colorMatrixLeft * colorL.rgb +',
				'			colorMatrixRight * colorR.rgb, 0., 1. );',

				'	gl_FragColor = vec4(',
				'			color.r, color.g, color.b,',
				'			max( colorL.a, colorR.a ) );',

				'	#include <tonemapping_fragment>',
				'	#include <colorspace_fragment>',

				'}'

			].join( '\n' )

		} );

		const _mesh = new Mesh( new PlaneGeometry( 2, 2 ), _material );
		_scene.add( _mesh );

		this.setSize = function ( width, height ) {

			renderer.setSize( width, height );

			const pixelRatio = renderer.getPixelRatio();

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

		};

		this.render = function ( scene, camera ) {

			const currentRenderTarget = renderer.getRenderTarget();

			if ( scene.matrixWorldAutoUpdate === true ) scene.updateMatrixWorld();

			if ( camera.parent === null && camera.matrixWorldAutoUpdate === true ) 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 );

			renderer.setRenderTarget( currentRenderTarget );

		};

		this.dispose = function () {

			_renderTargetL.dispose();
			_renderTargetR.dispose();
			_mesh.geometry.dispose();
			_mesh.material.dispose();

		};

	}

}

export { AnaglyphEffect };