A nonuniform rational B-Spline curve defined by

where is the order, are the B-Spline basis functions, are control points, and the weight of is the last ordinate of the homogeneous point . These curves are closed under perspective transformations and can represent Conic Sections exactly.

**References**

Piegl, L. and Tiller, W. *The NURBS Book, 2nd ed* New York: Springer-Verlag, 1997.

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1999-05-25