function TileBoundingSphere(center, radius) {
  if (radius === 0) {
    radius = CesiumMath.EPSILON7;
  }
  this._boundingSphere = new BoundingSphere(center, radius);
}
A tile bounding volume specified as a sphere.
@alias TileBoundingSphere
@constructor

@param {Cartesian3} [center=Cartesian3.ZERO] The center of the bounding sphere.
@param {number} [radius=0.0] The radius of the bounding sphere.

@private