Physics

gistfile1.js

function Physics(args) {
	var pixelsPerMeter=args.ptm;
	function px(x){
		return x*pixelsPerMeter;
	}
	function meters(x){
		return x/pixelsPerMeter;
	}
	function Body(args) {
		var self = Class({
			b2Body:args.body,
			physics:args.physics,
			init: function() {
				return self;
			},
			bodyType:args.bodyType,
			shapeType:args.shapeType,
			get x() {
				return px(self.body.GetPosition().x);
			},
			get y() {
				return px(self.body.GetPosition().y);
			},
			set x(x) {
				self.body.SetPosition(new b2Vec2(meters(x), meters(self.y)));
			},
			set y(y) {
				self.body.SetPosition(new b2Vec2(meters(self.x), meters(y)));
			},
			get vx() {
				return px(self.body.GetLinearVelocity().x);
			},
			get vy() {
				return px(self.body.GetLinearVelocity().y);
			},
			set vx(x) {
				self.body.SetLinearVelocity(new b2Vec2(meters(x), meters(self.vy)));
			},
			set vy(y) {
				self.body.SetLinearVelocity(new b2Vec2(meters(self.vx), meters(y)));
			},
			apply:function(x,y){
				self.body.ApplyForce(new b2Vec2(meters(x),meters(y)),self.body.GetWorldCenter());
			}
		});
		return self.init();
	}
	var self = Class({
		world:null,
		ptm:null,
		init: function() {
			return self;
			self.world=new b2World(new b2Vec2(0, .1), false);
		},
		update:function(){
			self.world.Step( 1000/60, 10 );
			self.world.DrawDebugData();
			self.world.ClearForces();
		},
		body:function(args) {
			var fixDef = new b2FixtureDef();
			fixDef.density = 1.0;
			fixDef.friction = 0.5;
			fixDef.restitution = 0.2;
			var bodyDef = new b2BodyDef();
			bodyDef.type = b2Body.b2_dynamicBody;
			switch (args.shapeType) {
				case "CIRCLE":
					fixDef.shape = new b2CircleShape(args.radius);
				break;
				case "POLYGON":
					fixDef.shape = new b2PolygonShape();
					fixDef.shape.SetAsBox((32).toMeters() / 2, (32).toMeters() / 2);
				break;
				case "BOX":
					fixDef.shape = new b2PolygonShape();
					fixDef.shape.SetAsBox((args.width).toMeters() / 2, (args.height).toMeters() / 2);				
				break;
				var body = self.world.CreateBody(bodyDef);
				body.CreateFixture(fixDef);
				return Body({
					body:body,
					shapeType:args.shapeType,
					physics:self,
				});
			}
		}
	});
	return self.init();
}