<P> In computational geometry, the point - in - polygon (PIP) problem asks whether a given point in the plane lies inside, outside, or on the boundary of a polygon . It is a special case of point location problems and finds applications in areas that deal with processing geometrical data, such as computer graphics, computer vision, geographical information systems (GIS), motion planning, and CAD . </P> <P> An early description of the problem in computer graphics shows two common approaches (ray casting and angle summation) in use as early as 1974 . </P>

What test would you use to decide if a figure is or is not a polygon