docs: function init(_scene, _camera, _params) {
  	if (!_scene || !(_scene instanceof THREE.Scene)) {
  		throw new TypeError('Requires THREE.Scene argument');
  	}
  	if (!_camera || !(_camera instanceof THREE.Camera)) {
  		throw new TypeError('Requires THREE.Camera argument');
  	}
  	scene = _scene;
  	camera = _camera;
  
  	var p = _params || {};
  	domElem = p.renderer && p.renderer.domElement || window;
  
  	domElem.addEventListener('mousedown', mouseDown, false);
  	domElem.addEventListener('mouseup', mouseUp, false);
  	domElem.addEventListener('mousemove', mouseMove, false);
  }