examples/webgl_shadow_contact.html

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		<title>three.js webgl - contact shadows</title>
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		<div id="info">
			<a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> webgl - contact shadows
		</div>
		<!-- Import maps polyfill -->
		<!-- Remove this when import maps will be widely supported -->
		<script async src="https://unpkg.com/es-module-shims@1.3.6/dist/es-module-shims.js"></script>

		<script type="importmap">
			{
				"imports": {
					"three": "../build/three.module.js",
					"three/addons/": "./jsm/"
				}
			}
		</script>

		<script type="module">

			import * as THREE from 'three';
			import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
			import Stats from 'three/addons/libs/stats.module.js';
			import { GUI } from 'three/addons/libs/lil-gui.module.min.js';
			import { HorizontalBlurShader } from 'three/addons/shaders/HorizontalBlurShader.js';
			import { VerticalBlurShader } from 'three/addons/shaders/VerticalBlurShader.js';

			let camera, scene, renderer, stats, gui;

			const meshes = [];

			const PLANE_WIDTH = 2.5;
			const PLANE_HEIGHT = 2.5;
			const CAMERA_HEIGHT = 0.3;

			const state = {
				shadow: {
					blur: 3.5,
					darkness: 1,
					opacity: 1,
				},
				plane: {
					color: '#ffffff',
					opacity: 1,
				},
				showWireframe: false,
			};

			let shadowGroup, renderTarget, renderTargetBlur, shadowCamera, cameraHelper, depthMaterial, horizontalBlurMaterial, verticalBlurMaterial;

			let plane, blurPlane, fillPlane;

			init();
			animate();

			function init() {

				camera = new THREE.PerspectiveCamera( 50, window.innerWidth / window.innerHeight, 0.1, 100 );
				camera.position.set( 0.5, 1, 2 );

				scene = new THREE.Scene();
				scene.background = new THREE.Color( 0xffffff );

				stats = new Stats();
				document.body.appendChild( stats.dom );

				window.addEventListener( 'resize', onWindowResize );

				// add the example meshes

				const geometries = [
					new THREE.BoxGeometry( 0.4, 0.4, 0.4 ),
					new THREE.IcosahedronGeometry( 0.3 ),
					new THREE.TorusKnotGeometry( 0.4, 0.05, 256, 24, 1, 3 )
				];

				const material = new THREE.MeshNormalMaterial();

				for ( let i = 0, l = geometries.length; i < l; i ++ ) {

					const angle = ( i / l ) * Math.PI * 2;

					const geometry = geometries[ i ];
					const mesh = new THREE.Mesh( geometry, material );
					mesh.position.y = 0.1;
					mesh.position.x = Math.cos( angle ) / 2.0;
					mesh.position.z = Math.sin( angle ) / 2.0;
					scene.add( mesh );
					meshes.push( mesh );

				}


				// the container, if you need to move the plane just move this
				shadowGroup = new THREE.Group();
				shadowGroup.position.y = - 0.3;
				scene.add( shadowGroup );

				// the render target that will show the shadows in the plane texture
				renderTarget = new THREE.WebGLRenderTarget( 512, 512 );
				renderTarget.texture.generateMipmaps = false;

				// the render target that we will use to blur the first render target
				renderTargetBlur = new THREE.WebGLRenderTarget( 512, 512 );
				renderTargetBlur.texture.generateMipmaps = false;


				// make a plane and make it face up
				const planeGeometry = new THREE.PlaneGeometry( PLANE_WIDTH, PLANE_HEIGHT ).rotateX( Math.PI / 2 );
				const planeMaterial = new THREE.MeshBasicMaterial( {
					map: renderTarget.texture,
					opacity: state.shadow.opacity,
					transparent: true,
					depthWrite: false,
				} );
				plane = new THREE.Mesh( planeGeometry, planeMaterial );
				// make sure it's rendered after the fillPlane
				plane.renderOrder = 1;
				shadowGroup.add( plane );

				// the y from the texture is flipped!
				plane.scale.y = - 1;

				// the plane onto which to blur the texture
				blurPlane = new THREE.Mesh( planeGeometry );
				blurPlane.visible = false;
				shadowGroup.add( blurPlane );

				// the plane with the color of the ground
				const fillPlaneMaterial = new THREE.MeshBasicMaterial( {
					color: state.plane.color,
					opacity: state.plane.opacity,
					transparent: true,
					depthWrite: false,
				} );
				fillPlane = new THREE.Mesh( planeGeometry, fillPlaneMaterial );
				fillPlane.rotateX( Math.PI );
				shadowGroup.add( fillPlane );

				// the camera to render the depth material from
				shadowCamera = new THREE.OrthographicCamera( - PLANE_WIDTH / 2, PLANE_WIDTH / 2, PLANE_HEIGHT / 2, - PLANE_HEIGHT / 2, 0, CAMERA_HEIGHT );
				shadowCamera.rotation.x = Math.PI / 2; // get the camera to look up
				shadowGroup.add( shadowCamera );

				cameraHelper = new THREE.CameraHelper( shadowCamera );

				// like MeshDepthMaterial, but goes from black to transparent
				depthMaterial = new THREE.MeshDepthMaterial();
				depthMaterial.userData.darkness = { value: state.shadow.darkness };
				depthMaterial.onBeforeCompile = function ( shader ) {

					shader.uniforms.darkness = depthMaterial.userData.darkness;
					shader.fragmentShader = /* glsl */`
						uniform float darkness;
						${shader.fragmentShader.replace(
					'gl_FragColor = vec4( vec3( 1.0 - fragCoordZ ), opacity );',
					'gl_FragColor = vec4( vec3( 0.0 ), ( 1.0 - fragCoordZ ) * darkness );'
				)}
					`;

				};

				depthMaterial.depthTest = false;
				depthMaterial.depthWrite = false;

				horizontalBlurMaterial = new THREE.ShaderMaterial( HorizontalBlurShader );
				horizontalBlurMaterial.depthTest = false;

				verticalBlurMaterial = new THREE.ShaderMaterial( VerticalBlurShader );
				verticalBlurMaterial.depthTest = false;

				//

				gui = new GUI();
				const shadowFolder = gui.addFolder( 'shadow' );
				shadowFolder.open();
				const planeFolder = gui.addFolder( 'plane' );
				planeFolder.open();


				shadowFolder.add( state.shadow, 'blur', 0, 15, 0.1 );
				shadowFolder.add( state.shadow, 'darkness', 1, 5, 0.1 ).onChange( function () {

					depthMaterial.userData.darkness.value = state.shadow.darkness;

				} );
				shadowFolder.add( state.shadow, 'opacity', 0, 1, 0.01 ).onChange( function () {

					plane.material.opacity = state.shadow.opacity;

				} );
				planeFolder.addColor( state.plane, 'color' ).onChange( function () {

					fillPlane.material.color = new THREE.Color( state.plane.color );

				} );
				planeFolder.add( state.plane, 'opacity', 0, 1, 0.01 ).onChange( function () {

					fillPlane.material.opacity = state.plane.opacity;

				} );

				gui.add( state, 'showWireframe', true ).onChange( function () {

					if ( state.showWireframe ) {

						scene.add( cameraHelper );

					} else {

						scene.remove( cameraHelper );

					}

				} );

				//

				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				document.body.appendChild( renderer.domElement );

				//

				new OrbitControls( camera, renderer.domElement );

			}

			function onWindowResize() {

				camera.aspect = window.innerWidth / window.innerHeight;
				camera.updateProjectionMatrix();

				renderer.setSize( window.innerWidth, window.innerHeight );

			}

			// renderTarget --> blurPlane (horizontalBlur) --> renderTargetBlur --> blurPlane (verticalBlur) --> renderTarget
			function blurShadow( amount ) {

				blurPlane.visible = true;

				// blur horizontally and draw in the renderTargetBlur
				blurPlane.material = horizontalBlurMaterial;
				blurPlane.material.uniforms.tDiffuse.value = renderTarget.texture;
				horizontalBlurMaterial.uniforms.h.value = amount * 1 / 256;

				renderer.setRenderTarget( renderTargetBlur );
				renderer.render( blurPlane, shadowCamera );

				// blur vertically and draw in the main renderTarget
				blurPlane.material = verticalBlurMaterial;
				blurPlane.material.uniforms.tDiffuse.value = renderTargetBlur.texture;
				verticalBlurMaterial.uniforms.v.value = amount * 1 / 256;

				renderer.setRenderTarget( renderTarget );
				renderer.render( blurPlane, shadowCamera );

				blurPlane.visible = false;

			}

			function animate( ) {

				requestAnimationFrame( animate );

				//

				meshes.forEach( mesh => {

					mesh.rotation.x += 0.01;
					mesh.rotation.y += 0.02;

				} );

				//

				// remove the background
				const initialBackground = scene.background;
				scene.background = null;

				// force the depthMaterial to everything
				cameraHelper.visible = false;
				scene.overrideMaterial = depthMaterial;

				// set renderer clear alpha
				const initialClearAlpha = renderer.getClearAlpha();
				renderer.setClearAlpha( 0 );

				// render to the render target to get the depths
				renderer.setRenderTarget( renderTarget );
				renderer.render( scene, shadowCamera );

				// and reset the override material
				scene.overrideMaterial = null;
				cameraHelper.visible = true;

				blurShadow( state.shadow.blur );

				// a second pass to reduce the artifacts
				// (0.4 is the minimum blur amout so that the artifacts are gone)
				blurShadow( state.shadow.blur * 0.4 );

				// reset and render the normal scene
				renderer.setRenderTarget( null );
				renderer.setClearAlpha( initialClearAlpha );
				scene.background = initialBackground;

				renderer.render( scene, camera );
				stats.update();

			}

		</script>
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