Doodle3D-Slicer/three.js-master/examples/js/Cloth.js

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2015-06-12 15:58:26 +02:00
/*
* Cloth Simulation using a relaxed constrains solver
*/
// Suggested Readings
// Advanced Character Physics by Thomas Jakobsen Character
// http://freespace.virgin.net/hugo.elias/models/m_cloth.htm
// http://en.wikipedia.org/wiki/Cloth_modeling
// http://cg.alexandra.dk/tag/spring-mass-system/
// Real-time Cloth Animation http://www.darwin3d.com/gamedev/articles/col0599.pdf
var DAMPING = 0.03;
var DRAG = 1 - DAMPING;
var MASS = .1;
var restDistance = 25;
var xSegs = 10; //
var ySegs = 10; //
var clothFunction = plane(restDistance * xSegs, restDistance * ySegs);
var cloth = new Cloth(xSegs, ySegs);
var GRAVITY = 981 * 1.4; //
var gravity = new THREE.Vector3( 0, -GRAVITY, 0 ).multiplyScalar(MASS);
var TIMESTEP = 18 / 1000;
var TIMESTEP_SQ = TIMESTEP * TIMESTEP;
var pins = [];
var wind = true;
var windStrength = 2;
var windForce = new THREE.Vector3(0,0,0);
var ballPosition = new THREE.Vector3(0, -45, 0);
var ballSize = 60; //40
var tmpForce = new THREE.Vector3();
var lastTime;
function plane(width, height) {
return function(u, v) {
var x = (u - 0.5) * width;
var y = (v + 0.5) * height;
var z = 0;
return new THREE.Vector3(x, y, z);
};
}
function Particle(x, y, z, mass) {
this.position = clothFunction(x, y); // position
this.previous = clothFunction(x, y); // previous
this.original = clothFunction(x, y);
this.a = new THREE.Vector3(0, 0, 0); // acceleration
this.mass = mass;
this.invMass = 1 / mass;
this.tmp = new THREE.Vector3();
this.tmp2 = new THREE.Vector3();
}
// Force -> Acceleration
Particle.prototype.addForce = function(force) {
this.a.add(
this.tmp2.copy(force).multiplyScalar(this.invMass)
);
};
// Performs verlet integration
Particle.prototype.integrate = function(timesq) {
var newPos = this.tmp.subVectors(this.position, this.previous);
newPos.multiplyScalar(DRAG).add(this.position);
newPos.add(this.a.multiplyScalar(timesq));
this.tmp = this.previous;
this.previous = this.position;
this.position = newPos;
this.a.set(0, 0, 0);
}
var diff = new THREE.Vector3();
function satisifyConstrains(p1, p2, distance) {
diff.subVectors(p2.position, p1.position);
var currentDist = diff.length();
if (currentDist == 0) return; // prevents division by 0
var correction = diff.multiplyScalar(1 - distance / currentDist);
var correctionHalf = correction.multiplyScalar(0.5);
p1.position.add(correctionHalf);
p2.position.sub(correctionHalf);
}
function Cloth(w, h) {
w = w || 10;
h = h || 10;
this.w = w;
this.h = h;
var particles = [];
var constrains = [];
var u, v;
// Create particles
for (v = 0; v <= h; v ++) {
for (u = 0; u <= w; u ++) {
particles.push(
new Particle(u / w, v / h, 0, MASS)
);
}
}
// Structural
for (v = 0; v < h; v ++) {
for (u = 0; u < w; u ++) {
constrains.push([
particles[index(u, v)],
particles[index(u, v + 1)],
restDistance
]);
constrains.push([
particles[index(u, v)],
particles[index(u + 1, v)],
restDistance
]);
}
}
for (u = w, v = 0; v < h; v ++) {
constrains.push([
particles[index(u, v)],
particles[index(u, v + 1)],
restDistance
]);
}
for (v = h, u = 0; u < w; u ++) {
constrains.push([
particles[index(u, v)],
particles[index(u + 1, v)],
restDistance
]);
}
// While many system uses shear and bend springs,
// the relax constrains model seem to be just fine
// using structural springs.
// Shear
// var diagonalDist = Math.sqrt(restDistance * restDistance * 2);
// for (v=0;v<h;v++) {
// for (u=0;u<w;u++) {
// constrains.push([
// particles[index(u, v)],
// particles[index(u+1, v+1)],
// diagonalDist
// ]);
// constrains.push([
// particles[index(u+1, v)],
// particles[index(u, v+1)],
// diagonalDist
// ]);
// }
// }
this.particles = particles;
this.constrains = constrains;
function index(u, v) {
return u + v * (w + 1);
}
this.index = index;
}
function simulate(time) {
if (!lastTime) {
lastTime = time;
return;
}
var i, il, particles, particle, pt, constrains, constrain;
// Aerodynamics forces
if (wind) {
var face, faces = clothGeometry.faces, normal;
particles = cloth.particles;
for (i = 0,il = faces.length; i < il; i ++) {
face = faces[i];
normal = face.normal;
tmpForce.copy(normal).normalize().multiplyScalar(normal.dot(windForce));
particles[face.a].addForce(tmpForce);
particles[face.b].addForce(tmpForce);
particles[face.c].addForce(tmpForce);
}
}
for (particles = cloth.particles, i = 0, il = particles.length
; i < il; i ++) {
particle = particles[i];
particle.addForce(gravity);
particle.integrate(TIMESTEP_SQ);
}
// Start Constrains
constrains = cloth.constrains,
il = constrains.length;
for (i = 0; i < il; i ++) {
constrain = constrains[i];
satisifyConstrains(constrain[0], constrain[1], constrain[2]);
}
// Ball Constrains
ballPosition.z = -Math.sin(Date.now() / 600) * 90 ; //+ 40;
ballPosition.x = Math.cos(Date.now() / 400) * 70
if (sphere.visible)
for (particles = cloth.particles, i = 0, il = particles.length
; i < il; i ++) {
particle = particles[i];
pos = particle.position;
diff.subVectors(pos, ballPosition);
if (diff.length() < ballSize) {
// collided
diff.normalize().multiplyScalar(ballSize);
pos.copy(ballPosition).add(diff);
}
}
// Floor Constains
for (particles = cloth.particles, i = 0, il = particles.length
; i < il; i ++) {
particle = particles[i];
pos = particle.position;
if (pos.y < -250) {
pos.y = -250;
}
}
// Pin Constrains
for (i = 0, il = pins.length; i < il; i ++) {
var xy = pins[i];
var p = particles[xy];
p.position.copy(p.original);
p.previous.copy(p.original);
}
}