A Processor for Bicubic Surface Patch Image Generation (NOT KNOWN IF PUBLISHED BECAUSE AUTHOR HAS LEFT AT&T)

This paper presents improvements to the subdivision algorithm for generating ray tracing images of bicubic surface patches in Bezier form. By using a set of tree transverse operators, our algorithm finds the "nearest" intersection between a surface patch and a ray by traversing the entire subdivision tree in preorder. This technique retains the advantage of subdivision and substantially reduces the circuit area by eliminating the need for a stack which is used to store control points of intermediate bicubic patches. To eliminate the multiplications needed in the subdivision iteration, an "intersection patch", a modification of the given bicubic surface patch, is used by the algorithm. The time needed to traverse the additional nodes that are required by the proposed algorithm is offset by the removal of the stack memory access time. A VLSI architecture based on the proposed algorithm is presented in detail. Its performance is analyzed and compared with the alternative approaches.