Controlling a computer display.

摘要

A system and method are provided for use in conjunction with a computer graphics system such that a single pass, or set of operations can be used to draw specific polygons contained within an image being displayed. The computer graphics system includes a multiple bit frame buffer (12), a write mask (16) which can disable at least two bits of the frame buffer, a z-buffer (20) capable of being turned off and a color map (10) 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 by the write mask, the hidden line color is selected from color map 10 and draws the polygon being considered with the selected color. The z-buffer is then turned on and with one bit plane disabled and another bit plane enabled by the write mask, the background color is selected from the color map. The polygon interior is then drawn with the background color previously selected, 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 from the color map and the polygon being considered is drawn. With the z-buffer turned on, any visible lines will take precedence over corresponding hidden lines or background colors having corresponding pixels. The next polygon to be considered is drawn using the same steps as previously discussed.