Removal of part of an object outside a polygon (see clipping). Efficient algorithms exist that pipeline the sequence of edges that define the polygon to the set of planes to be clipped against. Polygon clipping is particularly difficult because it is necessary that closed polygons remain closed. Clipping a polygon can result in several disjoint polygons. Typical algorithms include the Sutherland-Hodgman and the Weiler-Atherton clipping algorithms.