verlet
Version:
simple 2d physics for js.
164 lines (127 loc) • 4.86 kB
HTML
<html lang="en">
<head>
<title>Verlet Fractal Trees</title>
<meta charset="UTF-8" />
<link rel="stylesheet" href="../css/style.css" type="text/css" media="screen, projection" />
<link href='http://fonts.googleapis.com/css?family=Libre+Baskerville:400,700,400italic' rel='stylesheet' type='text/css'>
<script type="text/javascript" src="../js/verlet-1.0.0.js"></script>
</head>
<body>
<script type="text/javascript" src="../site/js/common.js"></script>
<div id="header">
<h1><a href="../">verlet-js</a> / <em>Fractal Tree</em></h1>
<div id="bsa">
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</div>
<p>
<h4>Author</h4>
<a href="http://subprotocol.com/">Sub Protocol</a>
<h4>Summary</h4>
Recursively generated fractal tree demonstrating both distance and angular constraints.
<h4>Source Code</h4>
<a href="https://github.com/subprotocol/verlet-js/blob/master/examples/tree.html">View on GitHub</a>
</p>
</div>
<canvas id="scratch" style="width: 800px; height: 500px;"></canvas>
<script type="text/javascript">
function lerp(a, b, p) {
return (b-a)*p + a;
}
VerletJS.prototype.tree = function(origin, depth, branchLength, segmentCoef, theta) {
var lineCoef = 0.7;
this.origin = origin;
this.base = new Particle(origin);
this.root = new Particle(origin.add(new Vec2(0,10)));
var composite = new this.Composite();
composite.particles.push(this.base);
composite.particles.push(this.root);
composite.pin(0);
composite.pin(1);
var branch = function(parent, i, nMax, coef, normal) {
var particle = new Particle(parent.pos.add(normal.scale(branchLength*coef)));
composite.particles.push(particle);
var dc = new DistanceConstraint(parent, particle, lineCoef);
dc.p = i/nMax; // a hint for drawing
composite.constraints.push(dc);
particle.leaf = !(i < nMax);
if (i < nMax)
{
var a = branch(particle, i+1, nMax, coef*coef, normal.rotate(new Vec2(0,0), -theta));
var b = branch(particle, i+1, nMax, coef*coef, normal.rotate(new Vec2(0,0), theta));
var jointStrength = lerp(0.7, 0, i/nMax);
composite.constraints.push(new AngleConstraint(parent, particle, a, jointStrength));
composite.constraints.push(new AngleConstraint(parent, particle, b, jointStrength));
}
return particle;
}
var firstBranch = branch(this.base, 0, depth, segmentCoef, new Vec2(0,-1));
composite.constraints.push(new AngleConstraint(this.root, this.base, firstBranch, 1));
// animates the tree at the beginning
var noise = 10;
var i;
for (i=0;i<composite.particles.length;++i)
composite.particles[i].pos.mutableAdd(new Vec2(Math.floor(Math.random()*noise, Math.floor(Math.random()*noise))));
this.composites.push(composite);
return composite;
}
window.onload = function() {
var canvas = document.getElementById("scratch");
// canvas dimensions
var width = parseInt(canvas.style.width);
var height = parseInt(canvas.style.height);
// retina
var dpr = window.devicePixelRatio || 1;
canvas.width = width*dpr;
canvas.height = height*dpr;
canvas.getContext("2d").scale(dpr, dpr);
// simulation
var sim = new VerletJS(width, height, canvas);
sim.gravity = new Vec2(0,0);
sim.friction = 0.98;
// entities
var tree1 = sim.tree(new Vec2(width/4,height-120), 5, 70, 0.95, (Math.PI/2)/3);
var tree2 = sim.tree(new Vec2(width - width/4,height-120), 5, 70, 0.95, (Math.PI/2)/3);
tree2.drawParticles = function(ctx, composite) {
var i;
for (i=0;i<composite.particles.length;++i) {
var particle = composite.particles[i];
if (particle.leaf) {
ctx.beginPath();
ctx.arc(particle.pos.x, particle.pos.y, 25, 0, 2*Math.PI);
ctx.fillStyle = "#679d7c";
ctx.fill();
}
}
}
tree2.drawConstraints = function(ctx, composite) {
var i;
ctx.save();
ctx.strokeStyle = "#543324";
ctx.lineCap = "round";
for (i=0;i<composite.constraints.length;++i) {
var constraint = composite.constraints[i];
if (!(constraint instanceof DistanceConstraint && typeof constraint.p != "undefined"))
continue;
ctx.beginPath();
ctx.moveTo(constraint.a.pos.x, constraint.a.pos.y);
ctx.lineTo(constraint.b.pos.x, constraint.b.pos.y);
ctx.lineWidth = lerp(10,2,constraint.p);
ctx.stroke();
}
ctx.restore();
}
// animation loop
var loop = function() {
sim.frame(16);
sim.draw();
requestAnimFrame(loop);
};
loop();
};
</script>
<div id="footer">
Copyright 2013 Sub Protocol and other contributors.
<br/><a href="http://subprotocol.com/">http://subprotocol.com/</a>
</div>
</body>