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+<html lang="en">
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+<head>
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+ <title>three.js webgpu - compute cloth</title>
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+ <meta charset="utf-8">
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+ <meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
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+ <link type="text/css" rel="stylesheet" href="main.css">
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+</head>
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+<body>
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+
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+<div id="info">
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+ <a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> webgpu - compute cloth<br/>
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+ Simple cloth simulation with a verlet system running in compute shaders
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+</div>
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+
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+<script type="importmap">
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+ {
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+ "imports": {
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+ "three": "../build/three.webgpu.js",
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+ "three/webgpu": "../build/three.webgpu.js",
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+ "three/tsl": "../build/three.tsl.js",
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+ "three/addons/": "./jsm/"
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+ }
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+ }
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+</script>
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+
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+<script type="module">
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+
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+ import * as THREE from 'three';
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+
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+ import { Fn, If, Return, instancedArray, instanceIndex, uniform, select, attribute, uint, Loop, float, transformNormalToView, cross, triNoise3D, time } from 'three/tsl';
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+
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+ import { GUI } from 'three/addons/libs/lil-gui.module.min.js';
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+ import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
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+ import { RGBELoader } from 'three/addons/loaders/RGBELoader.js';
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+
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+ let renderer, scene, camera, controls;
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+
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+ const clothWidth = 1;
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+ const clothHeight = 1;
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+ const clothNumSegmentsX = 30;
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+ const clothNumSegmentsY = 30;
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+ const sphereRadius = 0.15;
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+
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+ let vertexPositionBuffer, vertexForceBuffer, vertexParamsBuffer;
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+ let springVertexIdBuffer, springRestLengthBuffer, springForceBuffer;
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+ let springListBuffer;
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+ let computeSpringForces, computeVertexForces;
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+ let dampeningUniform, spherePositionUniform, stiffnessUniform, sphereUniform, windUniform;
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+ let vertexWireframeObject, springWireframeObject;
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+ let clothMesh, clothMaterial, sphere;
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+ let timeSinceLastStep = 0;
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+ let timestamp = 0;
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+ const verletVertices = [];
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+ const verletSprings = [];
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+ const verletVertexColumns = [];
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+
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+ const clock = new THREE.Clock();
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+
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+ const params = {
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+ wireframe: false,
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+ sphere: true,
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+ wind: 1.0,
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+ };
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+
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+ init();
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+
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+ async function init() {
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+
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+ renderer = new THREE.WebGPURenderer( { antialias: true } );
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+ renderer.setPixelRatio( window.devicePixelRatio );
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+ renderer.setSize( window.innerWidth, window.innerHeight );
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+ renderer.toneMapping = THREE.ACESFilmicToneMapping;
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+ renderer.toneMappingExposure = 1.35;
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+ document.body.appendChild( renderer.domElement );
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+
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+ scene = new THREE.Scene();
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+
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+ camera = new THREE.PerspectiveCamera( 40, window.innerWidth / window.innerHeight, 0.01, 10 );
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+ camera.position.set( - 1.6, - 0.1, - 1.6 );
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+
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+ controls = new OrbitControls( camera, renderer.domElement );
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+
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+ controls.target.set( 0, - 0.1, 0 );
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+ controls.minDistance = 1;
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+ controls.maxDistance = 3;
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+
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+ const rgbeLoader = new RGBELoader().setPath( 'textures/equirectangular/' );
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+
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+ const hdrTexture = await rgbeLoader.loadAsync( 'royal_esplanade_1k.hdr' );
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+ hdrTexture.mapping = THREE.EquirectangularReflectionMapping;
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+ scene.background = hdrTexture;
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+ scene.backgroundBlurriness = 0.5;
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+ scene.environment = hdrTexture;
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+
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+ setupCloth();
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+
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+ const gui = new GUI();
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+ gui.add( stiffnessUniform, 'value', 0.1, 0.5, 0.01 ).name( 'stiffness' );
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+ gui.add( params, 'wireframe' );
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+ gui.add( params, 'sphere' );
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+ gui.add( params, 'wind', 0, 5, 0.1 );
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+ const materialFolder = gui.addFolder( 'material' );
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+ materialFolder.addColor( clothMaterial, 'color' );
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+ materialFolder.add( clothMaterial, 'roughness', 0.0, 1, 0.01 );
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+ materialFolder.add( clothMaterial, 'sheen', 0.0, 1, 0.01 );
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+ materialFolder.add( clothMaterial, 'sheenRoughness', 0.0, 1, 0.01 );
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+ materialFolder.addColor( clothMaterial, 'sheenColor' );
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+
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+ window.addEventListener( 'resize', onWindowResize );
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+ controls.update();
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+
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+ renderer.setAnimationLoop( render );
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+
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+ }
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+
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+ function setupVerletGeometry() {
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+
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+ // this function sets up the geometry of the verlet system, a grid of vertices connected by springs
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+
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+ const addVerletVertex = ( x, y, z, isFixed ) => {
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+
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+ const id = verletVertices.length;
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+ const vertex = {
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+ id,
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+ position: new THREE.Vector3( x, y, z ),
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+ isFixed,
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+ springIds: [],
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+ };
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+ verletVertices.push( vertex );
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+ return vertex;
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+
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+ };
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+
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+ const addVerletSpring = ( vertex0, vertex1 ) => {
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+
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+ const id = verletSprings.length;
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+ const spring = {
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+ id,
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+ vertex0,
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+ vertex1
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+ };
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+ vertex0.springIds.push( id );
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+ vertex1.springIds.push( id );
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+ verletSprings.push( spring );
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+ return spring;
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+
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+ };
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+
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+ // create the cloth's verlet vertices
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+ for ( let x = 0; x <= clothNumSegmentsX; x ++ ) {
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+
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+ const column = [];
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+ for ( let y = 0; y <= clothNumSegmentsY; y ++ ) {
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+
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+ const posX = x * ( clothWidth / clothNumSegmentsX ) - clothWidth * 0.5;
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+ const posZ = y * ( clothHeight / clothNumSegmentsY );
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+ const isFixed = ( y === 0 ) && ( ( x % 5 ) === 0 ); // make some of the top vertices' positions fixed
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+ const vertex = addVerletVertex( posX, clothHeight * 0.5, posZ, isFixed );
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+ column.push( vertex );
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+
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+ }
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+
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+ verletVertexColumns.push( column );
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+
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+ }
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+
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+ // create the cloth's verlet springs
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+ for ( let x = 0; x <= clothNumSegmentsX; x ++ ) {
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+
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+ for ( let y = 0; y <= clothNumSegmentsY; y ++ ) {
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+
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+ const vertex0 = verletVertexColumns[ x ][ y ];
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+ if ( x > 0 ) addVerletSpring( vertex0, verletVertexColumns[ x - 1 ][ y ] );
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+ if ( y > 0 ) addVerletSpring( vertex0, verletVertexColumns[ x ][ y - 1 ] );
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+ if ( x > 0 && y > 0 ) addVerletSpring( vertex0, verletVertexColumns[ x - 1 ][ y - 1 ] );
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+ if ( x > 0 && y < clothNumSegmentsY ) addVerletSpring( vertex0, verletVertexColumns[ x - 1 ][ y + 1 ] );
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+
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+ // You can make the cloth more rigid by adding more springs between further apart vertices
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+ //if (x > 1) addVerletSpring(vertex0, verletVertexColumns[x - 2][y]);
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+ //if (y > 1) addVerletSpring(vertex0, verletVertexColumns[x][y - 2]);
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+
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+ }
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+
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+ }
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+
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+ }
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+
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+ function setupVerletVertexBuffers() {
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+
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+ // setup the buffers holding the vertex data for the compute shaders
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+
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+ const vertexCount = verletVertices.length;
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+
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+ const springListArray = [];
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+ // this springListArray will hold a list of spring ids, ordered by the id of the vertex affected by that spring.
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+ // this is so the compute shader that accumulates the spring forces for each vertex can efficiently iterate over all springs affecting that vertex
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+
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+ const vertexPositionArray = new Float32Array( vertexCount * 3 );
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+ const vertexParamsArray = new Uint32Array( vertexCount * 3 );
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+ // the params Array holds three values for each verlet vertex:
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+ // x: isFixed, y: springCount, z: springPointer
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+ // isFixed is 1 if the verlet is marked as immovable, 0 if not
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+ // springCount is the number of springs connected to that vertex
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+ // springPointer is the index of the first spring in the springListArray that is connected to that vertex
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+
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+ for ( let i = 0; i < vertexCount; i ++ ) {
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+
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+ const vertex = verletVertices[ i ];
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+ vertexPositionArray[ i * 3 ] = vertex.position.x;
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+ vertexPositionArray[ i * 3 + 1 ] = vertex.position.y;
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+ vertexPositionArray[ i * 3 + 2 ] = vertex.position.z;
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+ vertexParamsArray[ i * 3 ] = vertex.isFixed ? 1 : 0;
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+ if ( ! vertex.isFixed ) {
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+
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+ vertexParamsArray[ i * 3 + 1 ] = vertex.springIds.length;
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+ vertexParamsArray[ i * 3 + 2 ] = springListArray.length;
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+ springListArray.push( ...vertex.springIds );
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+
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+ }
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+
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+ }
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+
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+ vertexPositionBuffer = instancedArray( vertexPositionArray, 'vec3' ).setPBO( true ); // setPBO(true) is only important for the WebGL Fallback
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+ vertexForceBuffer = instancedArray( vertexCount, 'vec3' );
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+ vertexParamsBuffer = instancedArray( vertexParamsArray, 'uvec3' );
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+
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+ springListBuffer = instancedArray( new Uint32Array( springListArray ), 'uint' ).setPBO( true );
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+
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+ }
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+
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+ function setupVerletSpringBuffers() {
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+
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+ // setup the buffers holding the spring data for the compute shaders
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+
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+ const springCount = verletSprings.length;
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+
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+ const springVertexIdArray = new Uint32Array( springCount * 2 );
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+ const springRestLengthArray = new Float32Array( springCount );
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+
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+ for ( let i = 0; i < springCount; i ++ ) {
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+
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+ const spring = verletSprings[ i ];
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+ springVertexIdArray[ i * 2 ] = spring.vertex0.id;
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+ springVertexIdArray[ i * 2 + 1 ] = spring.vertex1.id;
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+ springRestLengthArray[ i ] = spring.vertex0.position.distanceTo( spring.vertex1.position );
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+
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+ }
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+
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+ springVertexIdBuffer = instancedArray( springVertexIdArray, 'uvec2' ).setPBO( true );
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+ springRestLengthBuffer = instancedArray( springRestLengthArray, 'float' );
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+ springForceBuffer = instancedArray( springCount * 3, 'vec3' ).setPBO( true );
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+
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+ }
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+
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+ function setupUniforms() {
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+
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+ dampeningUniform = uniform( 0.99 );
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+ spherePositionUniform = uniform( new THREE.Vector3( 0, 0, 0 ) );
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+ sphereUniform = uniform( 1.0 );
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+ windUniform = uniform( 1.0 );
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+ stiffnessUniform = uniform( 0.2 );
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+
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+ }
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+
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+ function setupComputeShaders() {
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+
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+ // This function sets up the compute shaders for the verlet simulation
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+ // There are two shaders that are executed for each simulation step
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+
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+ const vertexCount = verletVertices.length;
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+ const springCount = verletSprings.length;
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+
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+ // 1. computeSpringForces:
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+ // This shader computes a force for each spring, depending on the distance between the two vertices connected by that spring and the targeted rest length
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+ computeSpringForces = Fn( ()=>{
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+
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+ If( instanceIndex.greaterThanEqual( uint( springCount ) ), () => {
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+
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+ // compute Shaders are executed in groups of 64, so instanceIndex might be bigger than the amount of springs.
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+ // in that case, return.
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+ Return();
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+
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+ } );
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+
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+ const vertexIds = springVertexIdBuffer.element( instanceIndex );
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+ const restLength = springRestLengthBuffer.element( instanceIndex );
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+
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+ const vertex0Position = vertexPositionBuffer.element( vertexIds.x );
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+ const vertex1Position = vertexPositionBuffer.element( vertexIds.y );
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+
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+ const delta = vertex1Position.sub( vertex0Position ).toVar();
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+ const dist = delta.length().max( 0.000001 ).toVar();
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+ const force = dist.sub( restLength ).mul( stiffnessUniform ).mul( delta ).mul( 0.5 ).div( dist );
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+ springForceBuffer.element( instanceIndex ).assign( force );
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+
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+ } )().compute( springCount );
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+
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+ // 2. computeVertexForces:
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+ // This shader accumulates the force for each vertex.
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+ // First it iterates over all springs connected to this vertex and accumulates their forces.
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+ // Then it adds a gravital force, wind force, and the collision with the sphere.
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+ // In the end it adds the force to the vertex' position.
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+ computeVertexForces = Fn( ()=>{
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+
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+ If( instanceIndex.greaterThanEqual( uint( vertexCount ) ), () => {
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+
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+ // compute Shaders are executed in groups of 64, so instanceIndex might be bigger than the amount of vertices.
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+ // in that case, return.
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+ Return();
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+
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+ } );
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+
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+ const params = vertexParamsBuffer.element( instanceIndex ).toVar();
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+ const isFixed = params.x;
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+ const springCount = params.y;
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+ const springPointer = params.z;
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+
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+ If( isFixed, () => {
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+
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+ // don't need to calculate vertex forces if the vertex is set as immovable
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+ Return();
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+
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+ } );
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+
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+ const position = vertexPositionBuffer.element( instanceIndex ).toVar( 'vertexPosition' );
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+ const force = vertexForceBuffer.element( instanceIndex ).toVar( 'vertexForce' );
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+
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+ force.mulAssign( dampeningUniform );
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+
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+ const ptrStart = springPointer.toVar( 'ptrStart' );
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+ const ptrEnd = ptrStart.add( springCount ).toVar( 'ptrEnd' );
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+
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+ Loop( { start: ptrStart, end: ptrEnd, type: 'uint', condition: '<' }, ( { i } )=>{
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+
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+ const springId = springListBuffer.element( i ).toVar( 'springId' );
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+ const springForce = springForceBuffer.element( springId );
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+ const springVertexIds = springVertexIdBuffer.element( springId );
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+ const factor = select( springVertexIds.x.equal( instanceIndex ), 1.0, - 1.0 );
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+ force.addAssign( springForce.mul( factor ) );
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+
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+ } );
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+
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+ // gravity
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+ force.y.subAssign( 0.00005 );
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+
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+ // wind
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+ const noise = triNoise3D( position, 1, time ).sub( 0.2 ).mul( 0.0001 );
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+ const windForce = noise.mul( windUniform );
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+ force.z.subAssign( windForce );
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+
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+ // collision with sphere
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+ const deltaSphere = position.add( force ).sub( spherePositionUniform );
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+ const dist = deltaSphere.length();
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+ const sphereForce = float( sphereRadius ).sub( dist ).max( 0 ).mul( deltaSphere ).div( dist ).mul( sphereUniform );
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+ force.addAssign( sphereForce );
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+
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+ vertexForceBuffer.element( instanceIndex ).assign( force );
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+ vertexPositionBuffer.element( instanceIndex ).addAssign( force );
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+
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+ } )().compute( vertexCount );
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+
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+ }
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+
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+ function setupWireframe() {
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+
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+ // adds helpers to visualize the verlet system
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+
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+ // verlet vertex visualizer
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+ const vertexWireframeMaterial = new THREE.SpriteNodeMaterial();
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+ vertexWireframeMaterial.positionNode = vertexPositionBuffer.element( instanceIndex );
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+ vertexWireframeObject = new THREE.Mesh( new THREE.PlaneGeometry( 0.01, 0.01 ), vertexWireframeMaterial );
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+ vertexWireframeObject.frustumCulled = false;
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+ vertexWireframeObject.count = verletVertices.length;
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+ scene.add( vertexWireframeObject );
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+
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+
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+ // verlet spring visualizer
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+ const springWireframePositionBuffer = new THREE.BufferAttribute( new Float32Array( 6 ), 3, false );
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+ const springWireframeIndexBuffer = new THREE.BufferAttribute( new Uint32Array( [ 0, 1 ] ), 1, false );
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+ const springWireframeMaterial = new THREE.LineBasicNodeMaterial();
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+ springWireframeMaterial.positionNode = Fn( () => {
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+
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+ const vertexIds = springVertexIdBuffer.element( instanceIndex );
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+ const vertexId = select( attribute( 'vertexIndex' ).equal( 0 ), vertexIds.x, vertexIds.y );
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+ return vertexPositionBuffer.element( vertexId );
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+
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+ } )();
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+
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+ const springWireframeGeometry = new THREE.InstancedBufferGeometry();
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|
+ springWireframeGeometry.setAttribute( 'position', springWireframePositionBuffer );
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|
+ springWireframeGeometry.setAttribute( 'vertexIndex', springWireframeIndexBuffer );
|
|
|
+ springWireframeGeometry.instanceCount = verletSprings.length;
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|
+
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|
+ springWireframeObject = new THREE.Line( springWireframeGeometry, springWireframeMaterial );
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|
+ springWireframeObject.frustumCulled = false;
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|
|
+ springWireframeObject.count = verletSprings.length;
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|
+ scene.add( springWireframeObject );
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|
|
+
|
|
|
+ }
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|
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+
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|
|
+ function setupSphere() {
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+
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|
+ const geometry = new THREE.IcosahedronGeometry( sphereRadius * 0.95, 4 );
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|
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+ const material = new THREE.MeshStandardNodeMaterial();
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|
+ sphere = new THREE.Mesh( geometry, material );
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|
+ scene.add( sphere );
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|
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+
|
|
|
+ }
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+
|
|
|
+ function setupClothMesh() {
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|
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+
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+ // This function generates a three Geometry and Mesh to render the cloth based on the verlet systems position data.
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|
|
+ // Therefore it creates a plane mesh, in which each vertex will be centered in the center of 4 verlet vertices.
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|
+
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+ const vertexCount = clothNumSegmentsX * clothNumSegmentsY;
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|
+ const geometry = new THREE.BufferGeometry();
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+
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|
+ // verletVertexIdArray will hold the 4 verlet vertex ids that contribute to each geometry vertex's position
|
|
|
+ const verletVertexIdArray = new Uint32Array( vertexCount * 4 );
|
|
|
+ const indices = [];
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|
+
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|
|
+ const getIndex = ( x, y ) => {
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|
+
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|
|
+ return y * clothNumSegmentsX + x;
|
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|
+
|
|
|
+ };
|
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|
+
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|
|
+ for ( let x = 0; x < clothNumSegmentsX; x ++ ) {
|
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+
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|
+ for ( let y = 0; y < clothNumSegmentsX; y ++ ) {
|
|
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+
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|
|
+ const index = getIndex( x, y );
|
|
|
+ verletVertexIdArray[ index * 4 ] = verletVertexColumns[ x ][ y ].id;
|
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|
+ verletVertexIdArray[ index * 4 + 1 ] = verletVertexColumns[ x + 1 ][ y ].id;
|
|
|
+ verletVertexIdArray[ index * 4 + 2 ] = verletVertexColumns[ x ][ y + 1 ].id;
|
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|
+ verletVertexIdArray[ index * 4 + 3 ] = verletVertexColumns[ x + 1 ][ y + 1 ].id;
|
|
|
+
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|
|
+ if ( x > 0 && y > 0 ) {
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|
+
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|
|
+ indices.push( getIndex( x, y ), getIndex( x - 1, y ), getIndex( x - 1, y - 1 ) );
|
|
|
+ indices.push( getIndex( x, y ), getIndex( x - 1, y - 1 ), getIndex( x, y - 1 ) );
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+ const verletVertexIdBuffer = new THREE.BufferAttribute( verletVertexIdArray, 4, false );
|
|
|
+ const positionBuffer = new THREE.BufferAttribute( new Float32Array( vertexCount * 3 ), 3, false );
|
|
|
+ geometry.setAttribute( 'position', positionBuffer );
|
|
|
+ geometry.setAttribute( 'vertexIds', verletVertexIdBuffer );
|
|
|
+ geometry.setIndex( indices );
|
|
|
+
|
|
|
+ clothMaterial = new THREE.MeshPhysicalNodeMaterial( {
|
|
|
+ side: THREE.DoubleSide,
|
|
|
+ transparent: true,
|
|
|
+ opacity: 0.85,
|
|
|
+ sheen: 1.0,
|
|
|
+ sheenRoughness: 0.5,
|
|
|
+ sheenColor: new THREE.Color( 0xffffff ),
|
|
|
+ } );
|
|
|
+
|
|
|
+ clothMaterial.positionNode = Fn( ( { material } ) => {
|
|
|
+
|
|
|
+ // gather the position of the 4 verlet vertices and calculate the center position and normal from that
|
|
|
+ const vertexIds = attribute( 'vertexIds' );
|
|
|
+ const v0 = vertexPositionBuffer.element( vertexIds.x ).toVar();
|
|
|
+ const v1 = vertexPositionBuffer.element( vertexIds.y ).toVar();
|
|
|
+ const v2 = vertexPositionBuffer.element( vertexIds.z ).toVar();
|
|
|
+ const v3 = vertexPositionBuffer.element( vertexIds.w ).toVar();
|
|
|
+
|
|
|
+ const top = v0.add( v1 );
|
|
|
+ const right = v1.add( v3 );
|
|
|
+ const bottom = v2.add( v3 );
|
|
|
+ const left = v0.add( v2 );
|
|
|
+
|
|
|
+ const tangent = right.sub( left ).normalize();
|
|
|
+ const bitangent = bottom.sub( top ).normalize();
|
|
|
+
|
|
|
+ const normal = cross( tangent, bitangent );
|
|
|
+
|
|
|
+ // send the normalView from the vertex shader to the fragment shader
|
|
|
+ material.normalNode = transformNormalToView( normal ).toVarying();
|
|
|
+
|
|
|
+ return v0.add( v1 ).add( v2 ).add( v3 ).mul( 0.25 );
|
|
|
+
|
|
|
+ } )();
|
|
|
+
|
|
|
+ clothMesh = new THREE.Mesh( geometry, clothMaterial );
|
|
|
+ clothMesh.frustumCulled = false;
|
|
|
+ scene.add( clothMesh );
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+ function setupCloth() {
|
|
|
+
|
|
|
+ setupVerletGeometry();
|
|
|
+ setupVerletVertexBuffers();
|
|
|
+ setupVerletSpringBuffers();
|
|
|
+ setupUniforms();
|
|
|
+ setupComputeShaders();
|
|
|
+ setupWireframe();
|
|
|
+ setupSphere();
|
|
|
+ setupClothMesh();
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+ function onWindowResize() {
|
|
|
+
|
|
|
+ camera.aspect = window.innerWidth / window.innerHeight;
|
|
|
+
|
|
|
+ camera.updateProjectionMatrix();
|
|
|
+
|
|
|
+ renderer.setSize( window.innerWidth, window.innerHeight );
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+ function updateSphere() {
|
|
|
+
|
|
|
+ sphere.position.set( Math.sin( timestamp * 2.1 ) * 0.1, 0, Math.sin( timestamp * 0.8 ) );
|
|
|
+ spherePositionUniform.value.copy( sphere.position );
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+ async function render() {
|
|
|
+
|
|
|
+ sphere.visible = params.sphere;
|
|
|
+ sphereUniform.value = params.sphere ? 1 : 0;
|
|
|
+ windUniform.value = params.wind;
|
|
|
+ clothMesh.visible = ! params.wireframe;
|
|
|
+ vertexWireframeObject.visible = params.wireframe;
|
|
|
+ springWireframeObject.visible = params.wireframe;
|
|
|
+
|
|
|
+ const deltaTime = Math.min( clock.getDelta(), 1 / 60 ); // don't advance the time too far, for example when the window is out of focus
|
|
|
+ const stepsPerSecond = 360; // ensure the same amount of simulation steps per second on all systems, independent of refresh rate
|
|
|
+ const timePerStep = 1 / stepsPerSecond;
|
|
|
+
|
|
|
+ timeSinceLastStep += deltaTime;
|
|
|
+
|
|
|
+ while ( timeSinceLastStep >= timePerStep ) {
|
|
|
+
|
|
|
+ // run a verlet system simulation step
|
|
|
+ timestamp += timePerStep;
|
|
|
+ timeSinceLastStep -= timePerStep;
|
|
|
+ updateSphere();
|
|
|
+ await renderer.computeAsync( computeSpringForces );
|
|
|
+ await renderer.computeAsync( computeVertexForces );
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+ await renderer.renderAsync( scene, camera );
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+
|
|
|
+</script>
|
|
|
+</body>
|
|
|
+</html>
|
Nick
