Add cgal.

CGAL is a collaborative effort of several sites in Europe and Israel. The goal
is to make the most important of the solutions and methods developed in
computational geometry available to users in industry and academia in a C++
library. The goal is to provide easy access to useful, reliable geometric
algorithms.

The CGAL library contains:

• the Kernel with geometric primitives such as points, vectors, lines, predicates for testing things such as relative positions of points, and operations such as intersections and distance calculation.
• the Basic Library which is a collection of standard data structures and geometric algorithms, such as convex hull in 2D/3D, (Delaunay) triangulation in 2D/3D, planar map, polyhedron, smallest enclosing circle, and multidimensional query structures.
• the Support Library which offers interfaces to other packages, e.g., for visualisation, and I/O, and other support facilities.

WWW: http://www.cgal.org/