function QuadtreeOccluders(options) {
  this._ellipsoid = new EllipsoidalOccluder(options.ellipsoid, Cartesian3.ZERO);
}
A set of occluders that can be used to test quadtree tiles for occlusion.

@alias QuadtreeOccluders
@constructor
@private

@param {Ellipsoid} [options.ellipsoid=Ellipsoid.WGS84] The ellipsoid that potentially occludes tiles.