Patent ID: 7142224

Claim:
A polygon drawing apparatus which draws a polygon by performing intensity processing on a polygon to be drawn using an anti-aliasing method based on an intensity value generated by an intensity value generating device, said intensity value generating device comprising: an edge calculating device which calculates line intersection data associated with an intersecting portion between each of edges of the polygon to be drawn, for a given one scan line, using vertex coordinates of the polygon to be drawn, the line intersection data including a first pair of outside intersection and inside intersection that represent intersecting positions between said given one scan line and one of the edges that is located on an upstream side as viewed in a scanning direction, a second pair of outside intersection and inside intersection that represent intersection positions between said given one scan line and one of the edges that is located on a downstream side as viewed in the scanning direction, an increasing rate at which an intensity value increases from the outside intersection to the inside intersection of said first pair, and a decreasing rate at which the intensity value decreases from the inside intersection to the outside intersection of said second pair, wherein the line intersection data is determined based on trajectories obtained by dragging a diamond-like box between vertices of the polygon to be drawn, said diamond-like box having diagonal dimensions in two coordinate axis directions and each of the diagonal dimensions being equal to a arid width; and a scan line processing device which calculates with respect to said given one scan line the intensity value to be given to each portion of the polygon in the scanning direction, based on the line intersection data calculated for said given one scan line by said edge calculating devices, wherein said edge calculating device and said scan line processing device operate alternately during processing for said given one scan line, whereby a polygon is drawn.