... levels

It is interesting to note also that Marr (1980) had already commented on the importance of the $\sqrt{2}$ factor on psycho-visual grounds.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... routines

CGAL is a C++ library of algorithms and data structures for Computational Geometry, see www.cgal.org

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.