Scan line display of algebraic surfaces

Abstract

A robust algorithm is presented for scan line display of algebraic surfaces of arbitrary degree and topology. The algorithm correctly displays singularities of any complexity, even those missed by ray tracing or polygonization, and (for surfaces of degree less than eight) offers a significant speed improvement over ray tracing. Antialiasing can generally be accomplished very quickly. In addition to its typical function of shaded raster display, the algorithm is particularly adept at quickly plotting silhouette and intersection curves. A practical use for the algorithm is to display boolean combinations of algebraic half spaces, including blend surfaces.A new polynomial basis is introduced, referred to as the Bernstein pyramid polynomial basis, which enhances numerical stability and which simplifies several computations such as scan planesurface intersection and silhouette detection.