tickPhysics and timestep GC

[ashconnell]

the tickPhysics method instantiates a date object each tick, thrashing the GC. Three.js created a Clock utility which will help out a bit better

var clock = new THREE.Clock();
clock.start();

function tick () {
    requestAnimationFrame(tick);
    var delta = clock.getDelta(); // results in what you call a 'timestep'
}