A parallel scan conversion algorithm with anti-aliasing for a general-purpose ultracomputer

Popular approaches to speeding up scan conversion often employ parallel processing. Recently, several special-purpose parallel architectures have been suggested. We propose an alternative to these systems: the general-purpose ultracomputer, a parallel processor with many autonomous processing elements and a shared memory. The “serial semantics/parallel execution” feature of this architecture is exploited in the formulation of a scan conversion algorithm. Hidden surfaces are removed using a single scanline, z-buffer algorithm. Since exact anti-aliasing is inherently slow, a novel parallel anti-aliasing algorithm is presented in which subpixel coverage by edges is approximated using a look-up table. The ultimate intensity of a pixel is the weighted sum of the intensity contribution of the closest edge, that of the “losing” edges, and that of the background. The algorithm is fast and accurate, it is attractive even in a serial environment, and it avoids several artifacts that commonly occur in animated sequences.