NURBS is a flexible method of describing surfaces. It is exact when modeling conic aspheres, which is great news for optical engineers! This means that spheres, ellipses, paraboloids and hyperboloids can be exported and imported exactly.

Higher order aspheres are modeled using multiple lower-order polynomial segments, and arbitrary accuracy can be achieved by simply changing the number of spline segments and export tolerances. Before simply setting extreme values however, careful thought should be given to the performance of the component in its intended application, and to the manufacturing tolerances that can be achieved in practice.