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https://github.com/Doodle3D/Doodle3D-Slicer.git
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281 lines
5.6 KiB
JavaScript
Executable File
281 lines
5.6 KiB
JavaScript
Executable File
/*
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* Cloth Simulation using a relaxed constrains solver
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*/
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// Suggested Readings
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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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var DAMPING = 0.03;
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var DRAG = 1 - DAMPING;
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var MASS = .1;
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var restDistance = 25;
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var xSegs = 10; //
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var ySegs = 10; //
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var clothFunction = plane(restDistance * xSegs, restDistance * ySegs);
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var cloth = new Cloth(xSegs, ySegs);
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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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var TIMESTEP = 18 / 1000;
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var TIMESTEP_SQ = TIMESTEP * TIMESTEP;
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var pins = [];
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var wind = true;
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var windStrength = 2;
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var windForce = new THREE.Vector3(0,0,0);
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var ballPosition = new THREE.Vector3(0, -45, 0);
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var ballSize = 60; //40
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var tmpForce = new THREE.Vector3();
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var lastTime;
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function plane(width, height) {
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return function(u, v) {
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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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return new THREE.Vector3(x, y, z);
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};
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}
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function Particle(x, y, z, mass) {
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this.position = clothFunction(x, y); // position
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this.previous = clothFunction(x, y); // previous
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this.original = clothFunction(x, y);
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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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// Force -> Acceleration
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Particle.prototype.addForce = function(force) {
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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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// Performs verlet integration
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Particle.prototype.integrate = function(timesq) {
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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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this.tmp = this.previous;
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this.previous = this.position;
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this.position = newPos;
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this.a.set(0, 0, 0);
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}
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var diff = new THREE.Vector3();
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function satisifyConstrains(p1, p2, distance) {
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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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function Cloth(w, h) {
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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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var particles = [];
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var constrains = [];
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var u, v;
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// Create particles
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for (v = 0; v <= h; v ++) {
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for (u = 0; u <= w; u ++) {
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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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// Structural
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for (v = 0; v < h; v ++) {
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for (u = 0; u < w; u ++) {
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constrains.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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constrains.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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for (u = w, v = 0; v < h; v ++) {
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constrains.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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for (v = h, u = 0; u < w; u ++) {
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constrains.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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// While many system uses shear and bend springs,
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// the relax constrains model seem 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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// for (v=0;v<h;v++) {
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// for (u=0;u<w;u++) {
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// constrains.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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// constrains.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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this.particles = particles;
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this.constrains = constrains;
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function index(u, v) {
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return u + v * (w + 1);
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}
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this.index = index;
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}
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function simulate(time) {
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if (!lastTime) {
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lastTime = time;
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return;
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}
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var i, il, particles, particle, pt, constrains, constrain;
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// Aerodynamics forces
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if (wind) {
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var face, faces = clothGeometry.faces, normal;
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particles = cloth.particles;
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for (i = 0,il = faces.length; i < il; i ++) {
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face = faces[i];
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normal = face.normal;
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tmpForce.copy(normal).normalize().multiplyScalar(normal.dot(windForce));
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particles[face.a].addForce(tmpForce);
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particles[face.b].addForce(tmpForce);
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particles[face.c].addForce(tmpForce);
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}
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}
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for (particles = cloth.particles, i = 0, il = particles.length
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; i < il; i ++) {
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particle = particles[i];
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particle.addForce(gravity);
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particle.integrate(TIMESTEP_SQ);
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}
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// Start Constrains
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constrains = cloth.constrains,
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il = constrains.length;
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for (i = 0; i < il; i ++) {
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constrain = constrains[i];
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satisifyConstrains(constrain[0], constrain[1], constrain[2]);
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}
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// Ball Constrains
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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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if (sphere.visible)
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for (particles = cloth.particles, i = 0, il = particles.length
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; i < il; i ++) {
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particle = particles[i];
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pos = particle.position;
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diff.subVectors(pos, ballPosition);
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if (diff.length() < ballSize) {
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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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// Floor Constains
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for (particles = cloth.particles, i = 0, il = particles.length
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; i < il; i ++) {
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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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pos.y = -250;
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}
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}
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// Pin Constrains
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for (i = 0, il = pins.length; i < il; i ++) {
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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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