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index.html
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<html>
<head>
<title>N Bodies</title>
<style>
body { margin: 0; }
canvas { width: 100%; height: 100% }
</style>
</head>
<body>
<script src="js/three.min.js"></script>
<script src="js/OrbitControls.js"></script>
<script src="js/Stats.js"></script>
<script>
var stats = new Stats();
stats.setMode( 0 ); // 0: fps, 1: ms, 2: mb
// align top-left
stats.domElement.style.position = 'absolute';
stats.domElement.style.left = '0px';
stats.domElement.style.top = '0px';
document.body.appendChild( stats.domElement );
var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera( 30, window.innerWidth/window.innerHeight, 0.1, 1000 );
var clock = new THREE.Clock;
var renderer = new THREE.WebGLRenderer({antialias: true});
renderer.setSize( window.innerWidth, window.innerHeight );
document.body.appendChild( renderer.domElement );
camera.position.z = 400;
controls = new THREE.OrbitControls(camera, document, renderer.domElement);
var N = 500;
var MAX_DIM = 100;
var MAX_V = 10;
var SPHERE_RADIUS = 1;
var SPHERE_WIDTH_SEGS = 3;
var SPHERE_HEIGHT_SEGS = 2;
var GRAV_CONSTANT_ACCEL = 10;
// Returns a random number between min (inclusive) and max (exclusive)
function getRandomArbitrary(min, max) {
return Math.random() * (max - min) + min;
}
var material = new THREE.MeshBasicMaterial( { color: 0xffffff } );
var generateParticle = function() {
var particle = new THREE.SphereGeometry(SPHERE_RADIUS);
var sphere = new THREE.Mesh(particle, material);
sphere.position.x = getRandomArbitrary(-MAX_DIM, MAX_DIM);
sphere.position.y = getRandomArbitrary(-MAX_DIM, MAX_DIM);
sphere.position.z = getRandomArbitrary(-MAX_DIM, MAX_DIM);
sphere.userData.vx = getRandomArbitrary(-MAX_V, MAX_V);
sphere.userData.vy = getRandomArbitrary(-MAX_V, MAX_V);
sphere.userData.vz = getRandomArbitrary(-MAX_V, MAX_V);
sphere.userData.m = getRandomArbitrary(0.8, 8.0);
return sphere;
}
function removeFromScene(object) {
scene.remove(object);
}
function max(a, b) {
if (a > b) return a; else return b;
}
function updateParticles(particles) {
// var dt = clock.getDelta();
var dt = 1/60.0;
// console.log(dt);
for (var i = 0; i < N; i++) {
if (particles[i]) {
var sphere = particles[i];
sphere.position.x += sphere.userData.vx * dt;
sphere.position.y += sphere.userData.vy * dt;
sphere.position.z += sphere.userData.vz * dt;
for (var j = i + 1; j < N; j++) {
if (particles[j]) {
var sphere2 = particles[j];
var dx = sphere2.position.x - sphere.position.x;
var dy = sphere2.position.y - sphere.position.y;
var dz = sphere2.position.z - sphere.position.z;
var ds = Math.sqrt(dx * dx + dy * dy + dz * dz);
if (ds < (sphere.geometry.boundingSphere.radius + sphere2.geometry.boundingSphere.radius)) { // collision detected
// inelastic collision
var mass = sphere.userData.m + sphere2.userData.m;
var vx = (sphere.userData.vx * sphere.userData.m + sphere2.userData.vx * sphere2.userData.m) / mass;
var vy = (sphere.userData.vy * sphere.userData.m + sphere2.userData.vy * sphere2.userData.m) / mass;
var vz = (sphere.userData.vz * sphere.userData.m + sphere2.userData.vz * sphere2.userData.m) / mass;
sphere.userData.vx = vx;
sphere.userData.vy = vy;
sphere.userData.vz = vz;
sphere.userData.m = mass;
var scale = max(sphere.scale.x, sphere2.scale.x) + 0.1;
sphere.scale.x = scale;
sphere.scale.y = scale;
sphere.scale.z = scale;
removeFromScene(sphere2);
particles[j] = null;
} else {
var accel = GRAV_CONSTANT_ACCEL * sphere2.userData.m / (ds * ds); // f = GMm/r^2, a = Gm/r^2
sphere.userData.vx += (dx / ds) * accel * dt;
sphere.userData.vy += (dy / ds) * accel * dt;
sphere.userData.vz += (dz / ds) * accel * dt;
var accel = GRAV_CONSTANT_ACCEL * sphere.userData.m / (ds * ds);
sphere2.userData.vx -= (dx / ds) * accel * dt;
sphere2.userData.vy -= (dy / ds) * accel * dt;
sphere2.userData.vz -= (dz / ds) * accel * dt;
// console.log((dx / ds) * GRAV_CONSTANT_ACCEL / (ds * ds) * dt);
}
}
}
}
}
}
particles = [];
for (var i = 0; i < N; i++) {
var sphere = generateParticle();
scene.add(sphere);
particles.push(sphere);
}
var render = function () {
requestAnimationFrame( render );
stats.begin();
updateParticles(particles);
renderer.render(scene, camera);
stats.end();
};
render();
</script>
</body>
</html>