GTS stands for the GNU Triangulated Surface Library. It is an Open Source Free Software Library intended to provide a set of useful functions to deal with 3D surfaces meshed with interconnected triangles. The source code is available free of charge under the Free Software LGPL license.
The code is written entirely in C with an object-oriented approach based mostly on the design of GTK+. Careful attention is paid to performance related issues as the initial goal of GTS is to provide a simple and efficient library to scientists dealing with 3D computational surface meshes.
The major features of GTS are:
- Object oriented structure
- Delaunay triangulations
- Robust geometric predicates
- Wide variety of surface operations
- Multiresolution models
- Continuous level of detail
- Collision/Intersection capability
- Graph operations
- Metric operations
- Fast rendering
Via GTS@Sourceforge (Hat tip to Jordan Miller)
I think this is a great alternative to .stl format