“EXACT: algorithm and hardware architecture for an improved A-buffer” by Schilling and Straßer

The EXACT (EXact Area Coverage calculaTion) algorithm presented in this paper solves the Hidden Surface
Elimination (HSE) problem on the subpixel level.
The use of subpixel masks for anti-aliasing causes some
problems with the HSE on the pixel level that are difficult to overcome. The approximations of the well
known A-buffer algorithm are replaced by an exact solution that avoids erratic pixels along intersecting or
touching surfaces.
With EXACT the HSE problem on the subpixel level
is solved with the help of p-masks. P-masks (priority masks) are subpixel masks that indicate for each
subpixel which one of two given planes is closer to
the viewer. An algorithm to produce the p-masks in
an efficient way and its hardware implementation are
presented. The p-mask generator is used in a hardware
implementation of an A-buffer algorithm in the form of
a rendering pipeline. Of course the algorithm can also
be used in software to enhance an existing A-buffer
implementation.
The paper ends with the description of the list processing architecture for which the EXACT A-buffer has
been built1

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