Two-Dimensional Clipping

Abstract

Clipping is a process that subdivides each element of a picture to be displayed into its visible and invisible parts, thus allowing us to discard the invisible parts of the picture. In 2D, the clipping process can be applied to a variety of graphics primitives such as points, lines, polygons and curves. Clipping is performed with respect to a clipping boundary, which may be a convex or concave polygonal boundary. Clipping to a convex polygonal boundary is much simpler, thus we will start our discussion by looking at various algorithms that clip graphics primitives against a convex polygonal boundary. In its simplest form, a convex polygonal boundary consists of the four edges of the world window or the screen viewport. In this case, x _l (x-left), x _r (x-right), y _b (y-bottom) and y _t (y-top) represent the four extremities of this rectangular clipping boundary.