Ray Tracing Free-Form B-Spline Surfaces

We present a method for using ray tracing to render spline surfaces¿one that is suitable for any object generated from control vertices via tensor-product B-splines. The method derives from kajiya´s work on ray tracing procedurally defined surfaces1 and makes use of two preprocessing steps. One involves the controlvertex refinement recurrences due to Riesenfeld et. al.2, and the second generates a tree of nested bounding boxes. Intersection testing involves running Kajiya´s algorithm on the tree, followed by two to three (on the average) iterations of Newton´s method.