Method and apparatus for filling polygons displayed by a raster graphic

Abstract

Method and apparatus for filling polygons displayed by a color CRT monitor of a raster graphic system. A graphic controller produces control signals which control the mode of operation of the system, two of which are a fast polygon write, or fast-fill write, mode and a fast polygon display, or display fast-fill, mode. When the system is in the fast polygon write mode, the graphic controller reads fast-fill toggle bits from a frame memory of boundary pixels defining initial and terminal pixels of each fill element. The fast-fill toggle bits of boundary pixels are set if the toggle bit read from memory was not set and, if set, it will reset it. In the fast polygon display mode, the system senses the initial boundary pixel of each fill element by its fast-fill toggle bit being set and applies the color address of the initial boundary pixel to a color look-up memory until the terminal pixel of the fill element is read from the memory. Thereafter, the color address of each pixel of a horizontal scan line is applied to the color look-up memory in synchronization with the raster scan until another initial boundary pixel of another fill element is sensed, etc., or until the end of the horizontal scan line is reached.