Special purpose graphics instructions are provided to facilitate hidden surface elimination. A Z-buffer check instruction performs multiple, simultaneous unsigned-integer (ordinal) comparisons of newly computed distance (Z) values with the contents of a Z-buffer. Distances of points to be drawn are compared...http://www.google.com/patents/US5081698?utm_source=gb-gplus-sharePatent US5081698 - Method and apparatus for graphics display data manipulation
