Graphics Gems III (IBM Version)

II.5

FAST GENERATION OF CYCLIC SEQUENCES

Alan W. Paeth,     NeuralWare Incorporated, Pittsburgh, Pennsylvania

Publisher Summary

This chapter presents methods for cyclic production of both arbitrary values and of Boolean states. Free-running inner loops often require a sequence of values or conditions that repeat after every N steps. For instance, a technique for high-speed Z-buffer drawing must perform buffer swapping and housekeeping in cycles of three. When N is not a power of two, direct examination of a register’s low order bits may not be used to form a count modulo N. Similarly, a fast 2-D N-gon generator requires the cyclic production of a sequence of N values, with vertex N identical to vertex zero. The chapter presents compact methods ...