Polygon Clipping

The term clipping is used to describe the process of finding whether a line (or polygon) is intersected by another polygon. A major application of clipping is to decide whether certain constructs fall within the display window. We should point out here that one cannot rely on the display device to achieve clipping for two reasons. First, the display area may be only a subset of the display screen (for example, a part of the screen may be reserved for the display of text). Second, there is no uniform way by which points with invalid coordinates are displayed. Quite often a display device ignores the high order bits, so that the constructs wrap around the screen. Therefore, there is a need for algorithms to solve this problem explicitly.