Polygon-filling apparatus used in a scanning display unit and method of filling the same

A polygon-filling apparatus for use in a scanning display unit comprising:

• a list memory to store corner number data and apex-data of a polygon, which data have been sequentially transferred thereto,
• means to obtain a number of apexes of the polygon according to the apex-data, said apexes corresponding respectively to a maximal value and a minimal value along a direction perpendicular to a scanning line,
• polygon discriminating means to discriminate, based upon said number of maximal and minimal values, whether the polygon is one which marks off one continuous lot on each scanning line or is one which is capable of marking off two or more continuous lots on each scanning line,
• means to detect apexes from any other apex which corresponds to the maximum value and the minimum value of coordinates in a direction perpendicular to the scanning direction, respectively, based upon apex-data of a polygon which has been discriminated to mark off only one continuous lot on each scanning line by said polygon discriminating means,
• means to alternatively generate ridge data on the left side and the right side on each scanning line by independently interpolating between data indicative of neighboring apexes chained along the left side and the right side of the polygon, respectively, from the apex having the maximum value to the apex having the minimum value, or generate ridge data on the left side and the right side on each scanning line by independently interpolating between data indicative of neighboring apexes chained along the left side and the right side of the polygon, respectively, from the apex having the minimum value to the apex having the maximum value, and
• means to display the scanning line by filling a specific region on each scanning line between points where the scanning line intersects both ridge lines.