The maintainer of COG has left the WIAS. In the consequence, the WIAS is not able to give any support or to proceed any requests concerning COG. A mesh generation tool which is actively maintained and supported by WIAS is TetGen by Hang Si.
COG 2.1 is a 2D and 3D Delaunay grid generation package with local anisotropic refinement, based on a geometry interface which allows almost arbitrary geometries (solid modelling with boolean operations, funtional definition, pixmaps).
The tutorial contains working test code for the following and many other examples:
The public domain version can be downloaded.
Some general purpose C++ classes used in COG 2.1 have been separated into the C++ library WZ 1.1.
Interface differences with version 2.0: Coordinate transformation management changed, operations run, use renamed - use now cog resp. coguse.