MX.OrbitCamera = function(opt){
	var exports = {}, bound = false
	exports.opt = opt = defaults(opt, {
		el: window,                   // object to bind events on
		camera: scene.camera,         // camera object we'll be moving
		radius: 100,
		radiusRange: [ 10, 1000 ],
		rotationX: PI/2,
		rotationY: 0,
		center: { x: 0, y: 0, z: 0 },
		sensitivity: 10,              // moving 1 pixel is like moving N radians
		wheelSensitivity: 10,
		ease: 10,
	})
	var rx, ry, radius, px, py, epsilon = 1e-10, dragging = false
	exports.init = function(){
    ry = opt.rotationY
    rx = opt.rotationX
    radius = opt.radius
    exports.wheel = new wheel({
			el: opt.el,
			update: function(e, delta){
				opt.radius = clamp( opt.radius + delta * opt.wheelSensitivity, opt.radiusRange[0], opt.radiusRange[1] )
			},
		})
		exports.bind()
	}
	exports.toggle = function(state){
		if (state) exports.bind()
		else exports.unbind()
	}
	exports.bind = function(){
		if (bound) return;
		bound = true
		opt.el.addEventListener("mousedown", down)
		window.addEventListener("mousemove", move)
		window.addEventListener("mouseup", up)
		exports.wheel.unlock()
	}
	exports.unbind = function(){
		if (! bound) return;
		bound = false
		opt.el.removeEventListener("mousedown", down)
		window.removeEventListener("mousemove", move)
		window.removeEventListener("mouseup", up)
		exports.wheel.lock()
	}
	function down (e) {
	  px = e.pageX
	  py = e.pageY
	  dragging = true
	}
	function move (e) {
	  if (! dragging) return
	  exports.delta(px- e.pageX, py - e.pageY)
	  px = e.pageX
	  py = e.pageY
	}
	function up (e) {
	  dragging = false
	}
	exports.delta = function(x,y){
	  opt.rotationY += x/window.innerWidth * opt.sensitivity
	  opt.rotationX = clamp( opt.rotationX + y/window.innerHeight * opt.sensitivity, 0, PI)
	}
	exports.zoom = function(r){
	  opt.radius = r
	}
	exports.zoomDelta = function(r){
	  opt.radius += r
	}
	exports.move = function(y, x){
	  opt.rotationY = y
	  if (typeof x == "number") { opt.rotationX = x }
	}
	exports.update = function(){
	  if (abs(ry - opt.rotationY) > epsilon) {
      ry = avg(ry, opt.rotationY, opt.ease)
	  }
	  else {
	    ry = opt.rotationY
	  }
	  if (abs(rx - opt.rotationX) > epsilon) {
      rx = avg(rx, opt.rotationX, opt.ease)
	  }
	  else {
	    rx = opt.rotationX
	  }
	  if (abs(radius - opt.radius) > epsilon) {
	    radius = avg(radius, opt.radius, opt.ease)
	  }
	  else {
	    radius = opt.radius
	  }
		opt.camera.x = opt.center.x + radius * sin(rx) * cos(ry)
		opt.camera.z = opt.center.y + radius * sin(rx) * sin(ry)
		opt.camera.y = opt.center.z + radius * cos(rx)
 		opt.camera.rotationX = PI/2 - rx
 		opt.camera.rotationY = ry + PI/2
	}
	return exports
}