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Patent Title: Single pass hidden line removal using Z-buffers

Assignee: IBM
Patent Number: US5220646
Issue Date: 06-15-1993
Application Number:
File Date:04-30-1990

Abstract: An improved computer graphics system allows a single pass, or set of operations to draw specific polygons contained within an image being displayed. The computer graphics system includes a multiple bit frame buffer, a write mask which can disable at least two bits of the frame buffer, a z-buffer capable of being turned off and a color map which is loaded with a background, a visible line and a hidden line color. With the z-buffer turned off, and the first bit plane of the frame buffer enabled and the second bit plane of the frame buffer disabled, the hidden line color is selected. The z-buffer is then turned on and with one bit plane disabled and another bit plane enabled, the background color is then selected. The polygon interior is then drawn with the background color, however any pixels corresponding to previously drawn lines will not be painted with the background color because of the disablement of bit plane one. The visible line color is then selected and the polygon being considered is drawn.


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