Non-Uniform Rational B-Splines

As more and more ME CAD/CAM application programs start using B-splines to represent curves and surfaces, the need is arising for advanced CAD/CAM workstations which can generate realistic images of these curves and surfaces directly from the B-spline description. This article discusses the advantages of using B-splines (in particular trimmed nonuniform rational B-splines) in such applications and the advantages of having a workstation that can display them directly. The authors explain B-splines in an intuitive and largely nonmathematical way. Illustrations are given of mechanical parts which contain both geometric shapes and freeform surfaces and which were rendered directly from B-spline descriptions. These examples are compared to the usual method for rendering such objects to further Illustrate the advantages of rendering trimmed surfaces directly from the B-spline description.