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@@ -19,9 +19,6 @@
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<body>
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<div id="info">Simple Cloth Simulation<br/>
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Verlet integration with relaxed constraints<br/>
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- <a onclick="wind = !wind;">Wind</a> |
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- <a onclick="sphere.visible = !sphere.visible;">Ball</a> |
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- <a onclick="togglePins();">Pins</a>
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</div>
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<script src="../build/three.js"></script>
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@@ -29,11 +26,360 @@
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<script src="js/WebGL.js"></script>
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<script src="js/controls/OrbitControls.js"></script>
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<script src="js/libs/stats.min.js"></script>
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-
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- <script src="js/Cloth.js"></script>
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+ <script src="js/libs/dat.gui.min.js"></script>
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<script>
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+ /*
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+ * Cloth Simulation using a relaxed constraints solver
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+ */
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+
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+ // Suggested Readings
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+
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+ // Advanced Character Physics by Thomas Jakobsen Character
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+ // http://freespace.virgin.net/hugo.elias/models/m_cloth.htm
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+ // http://en.wikipedia.org/wiki/Cloth_modeling
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+ // http://cg.alexandra.dk/tag/spring-mass-system/
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+ // Real-time Cloth Animation http://www.darwin3d.com/gamedev/articles/col0599.pdf
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+
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+ var params = {
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+ enableWind: true,
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+ showBall: false,
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+ tooglePins: togglePins
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+ };
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+
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+ var DAMPING = 0.03;
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+ var DRAG = 1 - DAMPING;
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+ var MASS = 0.1;
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+ var restDistance = 25;
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+
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+ var xSegs = 10;
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+ var ySegs = 10;
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+
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+ var clothFunction = plane( restDistance * xSegs, restDistance * ySegs );
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+
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+ var cloth = new Cloth( xSegs, ySegs );
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+
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+ var GRAVITY = 981 * 1.4;
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+ var gravity = new THREE.Vector3( 0, - GRAVITY, 0 ).multiplyScalar( MASS );
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+
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+
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+ var TIMESTEP = 18 / 1000;
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+ var TIMESTEP_SQ = TIMESTEP * TIMESTEP;
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+
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+ var pins = [];
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+
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+ var windForce = new THREE.Vector3( 0, 0, 0 );
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+
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+ var ballPosition = new THREE.Vector3( 0, - 45, 0 );
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+ var ballSize = 60; //40
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+
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+ var tmpForce = new THREE.Vector3();
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+
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+ var lastTime;
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+
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+
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+ function plane( width, height ) {
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+
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+ return function ( u, v, target ) {
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+
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+ var x = ( u - 0.5 ) * width;
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+ var y = ( v + 0.5 ) * height;
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+ var z = 0;
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+
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+ target.set( x, y, z );
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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 Particle( x, y, z, mass ) {
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+
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+ this.position = new THREE.Vector3();
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+ this.previous = new THREE.Vector3();
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+ this.original = new THREE.Vector3();
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+ this.a = new THREE.Vector3( 0, 0, 0 ); // acceleration
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+ this.mass = mass;
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+ this.invMass = 1 / mass;
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+ this.tmp = new THREE.Vector3();
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+ this.tmp2 = new THREE.Vector3();
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+
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+ // init
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+
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+ clothFunction( x, y, this.position ); // position
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+ clothFunction( x, y, this.previous ); // previous
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+ clothFunction( x, y, this.original );
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+
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+ }
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+
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+ // Force -> Acceleration
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+
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+ Particle.prototype.addForce = function ( force ) {
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+
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+ this.a.add(
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+ this.tmp2.copy( force ).multiplyScalar( this.invMass )
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+ );
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+
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+ };
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+
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+
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+ // Performs Verlet integration
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+
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+ Particle.prototype.integrate = function ( timesq ) {
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+
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+ var newPos = this.tmp.subVectors( this.position, this.previous );
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+ newPos.multiplyScalar( DRAG ).add( this.position );
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+ newPos.add( this.a.multiplyScalar( timesq ) );
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+
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+ this.tmp = this.previous;
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+ this.previous = this.position;
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+ this.position = newPos;
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+
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+ this.a.set( 0, 0, 0 );
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+
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+ };
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+
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+
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+ var diff = new THREE.Vector3();
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+
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+ function satisfyConstraints( p1, p2, distance ) {
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+
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+ diff.subVectors( p2.position, p1.position );
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+ var currentDist = diff.length();
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+ if ( currentDist === 0 ) return; // prevents division by 0
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+ var correction = diff.multiplyScalar( 1 - distance / currentDist );
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+ var correctionHalf = correction.multiplyScalar( 0.5 );
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+ p1.position.add( correctionHalf );
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+ p2.position.sub( correctionHalf );
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+
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+ }
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+
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+
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+ function Cloth( w, h ) {
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+
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+ w = w || 10;
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+ h = h || 10;
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+ this.w = w;
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+ this.h = h;
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+
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+ var particles = [];
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+ var constraints = [];
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+
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+ var u, v;
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+
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+ // Create particles
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+ for ( v = 0; v <= h; v ++ ) {
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+
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+ for ( u = 0; u <= w; u ++ ) {
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+
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+ particles.push(
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+ new Particle( u / w, v / h, 0, MASS )
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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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+ // Structural
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+
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+ for ( v = 0; v < h; v ++ ) {
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+
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+ for ( u = 0; u < w; u ++ ) {
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+
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+ constraints.push( [
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+ particles[ index( u, v ) ],
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+ particles[ index( u, v + 1 ) ],
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+ restDistance
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+ ] );
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+
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+ constraints.push( [
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+ particles[ index( u, v ) ],
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+ particles[ index( u + 1, v ) ],
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+ restDistance
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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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+ for ( u = w, v = 0; v < h; v ++ ) {
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+
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+ constraints.push( [
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+ particles[ index( u, v ) ],
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+ particles[ index( u, v + 1 ) ],
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+ restDistance
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+
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+ ] );
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+
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+ }
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+
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+ for ( v = h, u = 0; u < w; u ++ ) {
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+
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+ constraints.push( [
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+ particles[ index( u, v ) ],
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+ particles[ index( u + 1, v ) ],
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+ restDistance
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+ ] );
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+
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+ }
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+
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+
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+ // While many systems use shear and bend springs,
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+ // the relaxed constraints model seems to be just fine
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+ // using structural springs.
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+ // Shear
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+ // var diagonalDist = Math.sqrt(restDistance * restDistance * 2);
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+
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+
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+ // for (v=0;v<h;v++) {
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+ // for (u=0;u<w;u++) {
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+
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+ // constraints.push([
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+ // particles[index(u, v)],
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+ // particles[index(u+1, v+1)],
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+ // diagonalDist
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+ // ]);
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+
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+ // constraints.push([
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+ // particles[index(u+1, v)],
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+ // particles[index(u, v+1)],
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+ // diagonalDist
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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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+ this.particles = particles;
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+ this.constraints = constraints;
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+
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+ function index( u, v ) {
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+
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+ return u + v * ( w + 1 );
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+
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+ }
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+
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+ this.index = index;
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+
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+ }
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+
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+ function simulate( time ) {
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+
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+ if ( ! lastTime ) {
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+
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+ lastTime = time;
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+ return;
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+
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+ }
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+
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+ var i, j, il, particles, particle, constraints, constraint;
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+
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+ // Aerodynamics forces
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+
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+ if ( params.enableWind ) {
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+
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+ var indx;
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+ var normal = new THREE.Vector3();
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+ var indices = clothGeometry.index;
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+ var normals = clothGeometry.attributes.normal;
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+
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+ particles = cloth.particles;
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+
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+ for ( i = 0, il = indices.count; i < il; i += 3 ) {
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+
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+ for ( j = 0; j < 3; j ++ ) {
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+
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+ indx = indices.getX( i + j );
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+ normal.fromBufferAttribute( normals, indx );
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+ tmpForce.copy( normal ).normalize().multiplyScalar( normal.dot( windForce ) );
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+ particles[ indx ].addForce( tmpForce );
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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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+ for ( particles = cloth.particles, i = 0, il = particles.length; i < il; i ++ ) {
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+
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+ particle = particles[ i ];
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+ particle.addForce( gravity );
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+
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+ particle.integrate( TIMESTEP_SQ );
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+
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+ }
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+
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+ // Start Constraints
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+
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+ constraints = cloth.constraints;
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+ il = constraints.length;
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+
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+ for ( i = 0; i < il; i ++ ) {
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+
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+ constraint = constraints[ i ];
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+ satisfyConstraints( constraint[ 0 ], constraint[ 1 ], constraint[ 2 ] );
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+
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+ }
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+
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+ // Ball Constraints
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+
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+ ballPosition.z = - Math.sin( Date.now() / 600 ) * 90; //+ 40;
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+ ballPosition.x = Math.cos( Date.now() / 400 ) * 70;
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+
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+ if ( params.showBall ) {
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+
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+ sphere.visible = true;
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+
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+ for ( particles = cloth.particles, i = 0, il = particles.length; i < il; i ++ ) {
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+
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+ particle = particles[ i ];
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+ var pos = particle.position;
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+ diff.subVectors( pos, ballPosition );
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+ if ( diff.length() < ballSize ) {
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+
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+ // collided
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+ diff.normalize().multiplyScalar( ballSize );
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+ pos.copy( ballPosition ).add( diff );
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+
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+ }
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+
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+ }
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+
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+ } else {
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+
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+ sphere.visible = false;
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+
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+ }
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+
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+
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+ // Floor Constraints
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+
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+ for ( particles = cloth.particles, i = 0, il = particles.length; i < il; i ++ ) {
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+
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+ particle = particles[ i ];
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+ pos = particle.position;
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+ if ( pos.y < - 250 ) {
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+
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+ pos.y = - 250;
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+
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+ }
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+
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+ }
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+
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+ // Pin Constraints
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+
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+ for ( i = 0, il = pins.length; i < il; i ++ ) {
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+
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+ var xy = pins[ i ];
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+ var p = particles[ xy ];
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+ p.position.copy( p.original );
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+ p.previous.copy( p.original );
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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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/* testing cloth simulation */
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var pinsFormation = [];
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@@ -55,10 +401,9 @@
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pins = pinsFormation[ 1 ];
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-
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function togglePins() {
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- pins = pinsFormation[ ~~ ( Math.random() * pinsFormation.length ) ];
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+ pins = pinsFormation[ ~ ~ ( Math.random() * pinsFormation.length ) ];
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}
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@@ -142,11 +487,9 @@
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scene.add( object );
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object.customDepthMaterial = new THREE.MeshDepthMaterial( {
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-
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depthPacking: THREE.RGBADepthPacking,
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map: clothTexture,
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alphaTest: 0.5
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-
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} );
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// sphere
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@@ -157,6 +500,7 @@
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sphere = new THREE.Mesh( ballGeo, ballMaterial );
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sphere.castShadow = true;
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sphere.receiveShadow = true;
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+ sphere.visible = false;
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scene.add( sphere );
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// ground
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@@ -243,7 +587,12 @@
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window.addEventListener( 'resize', onWindowResize, false );
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- sphere.visible = ! true;
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+ //
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+
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+ var gui = new dat.GUI();
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+ gui.add( params, 'enableWind' );
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+ gui.add( params, 'showBall' );
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+ gui.add( params, 'tooglePins' );
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}
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@@ -268,8 +617,8 @@
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var windStrength = Math.cos( time / 7000 ) * 20 + 40;
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- windForce.set( Math.sin( time / 2000 ), Math.cos( time / 3000 ), Math.sin( time / 1000 ) )
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- windForce.normalize()
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+ windForce.set( Math.sin( time / 2000 ), Math.cos( time / 3000 ), Math.sin( time / 1000 ) );
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+ windForce.normalize();
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windForce.multiplyScalar( windStrength );
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simulate( time );
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Mugen87