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The complexity of anti-aliased 3-D rendering systems can be controlled by using a tool-building approach like that of the UNIX text-processing tools. Such an approach requires a simple picture representation amenable to anti-aliasing that all rendering programs can produce, a compositing algorithm for that representation and a command language to piece together scenes. This paper advocates a representation that combines Porter and Duff's compositing algebra with a Z-buffer to provide simple anti-aliased 3-D compositing.
Tom Duff (Mon,) studied this question.