Hi all, After a deep research, I found the projetct CGAL, wich provides geometrical algorithm : voronoi diagram, convex hull, triangulation, etc. http://www.cgal.org/ They provide python bindings too ( http://cgal-python.gforge.inria.fr/ ) Do you think this could be used in qgis ? Or do you think the grass tools a sufficent ? Kimaidou