p2s
Version:
A JavaScript 2D physics engine.
131 lines (113 loc) • 4.69 kB
HTML
<html>
<head>
<title>Control demo - p2.js physics engine</title>
<script src="../build/p2.js"></script>
<script src="../build/p2.renderer.js"></script>
<link href="css/demo.css" rel="stylesheet"/>
<meta name="description" content="Top-down control of a circle.">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
</head>
<body>
<script>
var postStepHandler;
var size = 6;
function createStaticBox(world, x, y, width, height){
var body = new p2.Body({
position: [x, y]
});
body.addShape(new p2.Box({ width: width, height: height }));
world.addBody(body);
return body;
}
function shortestArc(a, b){
if (Math.abs(b-a) < Math.PI)
return b - a;
if (b > a)
return b-a-Math.PI * 2.0;
return b-a+Math.PI * 2.0;
}
// Create demo application
var app = new p2.WebGLRenderer({
setup: function(){
// Create the physics world
var world = new p2.World({
gravity : [0, 0]
});
this.setWorld(world);
// Add some boxes
for(var i=0; i<10; i++){
var boxBody = new p2.Body({
mass: 0.5,
damping: 0.99,
angularDamping: 0.99,
position: [
(Math.random() - 0.5) * size,
(Math.random() - 0.5) * size
],
angle: (Math.random() - 0.5) * Math.PI * 2
});
boxBody.addShape(new p2.Box({ width: 0.4, height: 0.4 }));
world.addBody(boxBody);
}
// Add walls
createStaticBox(world, -size/2, 0, 0.1, size)
createStaticBox(world, size/2, 0, 0.1, size)
createStaticBox(world, 0, -size/2, size, 0.1)
createStaticBox(world, 0, size/2, size, 0.1)
// Character
var characterBody = new p2.Body({
mass: 1
});
var characterShape = new p2.Circle({
radius: 0.5
});
characterBody.addShape(characterShape);
world.addBody(characterBody);
// Control body
var controlBody = new p2.Body({
type: p2.Body.KINEMATIC,
collisionResponse: false
});
var controlShape = new p2.Circle({
radius: 0.1
});
controlBody.addShape(controlShape);
world.addBody(controlBody);
// Constrain control to character
var constraint = new p2.RevoluteConstraint(controlBody, characterBody, {
localPivotA: [0, 0],
localPivotB: [0, 0],
maxForce: 40
});
constraint.setMaxBias(0); // emulate friction
world.addConstraint(constraint);
var gear = new p2.GearConstraint(controlBody, characterBody, {
maxTorque: 100
});
gear.setMaxBias(0);
world.addConstraint(gear);
var mouseDelta = p2.vec2.create();
world.on('postStep', postStepHandler = function(){
// turn the control body
p2.vec2.subtract(mouseDelta, app.mousePosition, characterBody.position);
controlBody.angularVelocity = 10 * shortestArc(characterBody.angle, Math.atan2(mouseDelta[1], mouseDelta[0]));
// drive towards the mouse
if(p2.vec2.distance(app.mousePosition, characterBody.position) < 0.5){
p2.vec2.set(controlBody.velocity, 0, 0);
} else {
p2.vec2.copy(controlBody.velocity, mouseDelta);
p2.vec2.normalize(controlBody.velocity, controlBody.velocity);
p2.vec2.scale(controlBody.velocity, controlBody.velocity, 3);
}
});
this.frame(0, 0, 7, 7);
},
teardown: function(){
world.off('postStep', postStepHandler);
}
});
</script>
</body>
</html>