Abstract: A system for clipping polygons representing three-dimensional objects to produce a representation of the portion of the objects in a desired viewing space is disclosed. A guardband space at least partially enclosing the viewing space is defined. The polygons are compared to the guardband space to determine which polygons intersect at least one of the guardband planes defining the guardband space. The intersecting polygons are also compared to the viewing space to determine if they intersect at least one of the viewing planes defining the viewing space. Only polygons intersecting both a viewing plane and a guardband plane are clipped.

Abstract: Boolean AND or OR operations that are functions of two variables can be performed without knowledge of one of the variables. In a computer graphics system utilizing a frame-buffer memory to refresh a display, a pixel processor using this technique can perform SET and CLEAR functions on the data stored in the memory in which only memory write cycles are required.