Representing Quadric Surfaces Using NURBS Surfaces

A method for representing quadric surfaces using NURBS is presented. By means of the necessary and sufficient conditions for NURBS cu-rves to precisely represent circular arcs and other conics, quadric surfaces can be represented by NURBS surfaces with fewer control vertices. The method can be used not only for NURBS surface representation of quadric surfaces, but also for rounding polyhedrons. Many examples are given in the paper.