A Comparison of Pixel Complexity in Composition Techniques for Sort-Last Rendering

Sort-last rendering is a method of parallelizing compute-intensive computer graphics; specifically, the primitives that describe a scene are first allocated to a set of renderers, and the rendered images are then composited to give the final image. This paper surveys six such techniques and compares their performance with active pixels, i.e., pixels that are covered by at least one primitive. Active pixels offer a uniform way of accounting for the time, space, and bandwidth costs in sort-last rendering. The comparison highlights the strengths of each technique. For example, tree composition has minimum work, binary-swap (hypercube) has minimum composition latency, direct pixel forwarding (mesh) has minimum bandwidth latency, and snooping (bus) has minimum bandwidth volume; binary-swap's bandwidth and composition latencies decrease, whereas the bandwidth volumes for direct pixel forwarding and snooping are constant, when the number of renderers increase; etc.