Visibility problems involve either computing visibility properties
of terrain from a given viewpoint, or computing visibility properties
of objects located on terrain.
VARIANT includes a module for solving point-to-point visibility
queries, and a module for viewshed computation;
a module for horizon computation is under development.
Such MT-clients are described in the following subsections.
[LEILA: DECIDERE COME METTERE LA QUESTIONE MODULI IMPLEMENTATI E NON]
Subsections