## Section: Software

### CGAL and Ipe

Participant : Sébastien Loriot.

In collaboration with L. Rineau and S. Pion, Geometrica . Work started by Nicolas Carrez, summer intern, 2005. http://www.cgal.org

cgal is a C++ library of geometric algorithms initially developed within two European projects (project ESPRIT IV LTR CGAL December 97 - June 98, project ESPRIT IV LTR GALIA november 99 - august 00) by a consortium of eight research teams from the following institutes: Universiteit Utrecht, Max-Planck Institut Saarbrücken, INRIA Sophia Antipolis, ETH Zürich, Tel Aviv University, Freie Universität Berlin, Universität Halle, RISC Linz. The goal of cgal is to make the solutions offered by the computational geometry community available to the industrial world and applied domains.

The IPE editor, see http://tclab.kaist.ac.kr/ipe , is a graphical editor which combines xfig like facilities together with standard Computational Geometry algorithms. It is intensively used by the computational geometry community for making presentations as well as illustrating papers.

Based on the 2D algorithms present in the CGAL library, we developed in C++ a set of plugins, so as to make the following algorithms available from ipe : triangulations (Delaunay, constrained Delaunay, regular) as well as their duals, a convex hull algorithm, polygon partitioning algorithms, polygon offset, arrangements of linear and degree two primitives. These plugins are available under the Open Source LGPL license, and are subject to the constraints of the underlying CGAL packages. They can be downloaded from http://cgal-ipelets.gforge.inria.fr .