Formally, Let R be a ring parallel to the shape plane, with
the radius r and the center C. The ring R is positioned
above the shape S with the height h and represented as a
sequence of m uniformly distant points, R = frjgmj
=1. We
define ij to be the angle between the segment rj ; pi and
the plain contains the shape S, see Figure 1. We define the
vector V iewj to be V iewj = fijgn i=1. The vector V iewj
can be seen as watching the shape S from one upper view
point, the point rj .