Subdivision Algorithm and Envelope for Wang-Ball Curves

By means of the dual function of Wang-Ball basis, this paper presents an explicit subdivision algorithm for the Wang-Ball curve (subdivision matrix). As an application, some combinational identities are given. The Marsden's identity of power basis in terms of the Wang-Ball basis is also derived. Using the conversion formula between Bernstein basis and Wang-Ball basis, the envelope of the Wang-Ball curves is constructed.