From http://www.cs.cmu.edu/~quake/triangle.html:

Triangle generates exact Delaunay triangulations, constrained Delaunay triangulations, conforming Delaunay triangulations, Voronoi diagrams, and high-quality triangular meshes. The latter can be generated with no small or large angles, and are thus suitable for finite element analysis.

The original Triangle code is intended to be compiled as a standalone application. Though it is possible to compile the code as a library by using the TRILIBRARY symbol, there are a couple of problems with the approach (for example printing error messages to console and the use of exit(1)).

The main goal of this project is to turn Triangle into a re-usable library and the introduction of a simplified C API.

The Triangle repository contains the following directory structure:

src/Triangle                 Original Triangle and aCute code and new Triangle C API
src/examples/triangle-cli    Command-line interface
src/examples/triangle-test   Simple test program

The static library code is based on the following sources:

• Triangle (version 1.6), released 07/28/2005
  Copyright 1993, 1995, 1997, 1998, 2002, 2005 Jonathan Richard Shewchuk
  http://www.cs.cmu.edu/~quake/triangle.html
• aCute (version 1.0), released 06/15/2009
  Copyright Hale Erten, Alper Üngör
  https://www.cise.ufl.edu/~ungor/aCute/download.html

If you don't want to use the aCute extension, add NO_ACUTE to preprocessor definitions.

A brief porting guide for the new API is available in the wiki.

Changes to Triangle:

• Remove non-ANSI function declarations (ANSI_DECLARATORS symbol no longer used)
• Remove all non-library code (TRILIBRARY symbol no longer used)
• Remove main triangulate function (NO_TIMER symbol no longer used)
• Move structure definitions to triangle.h header
• Move configuration (#define constants) to triangle_config.h header
• Create triangle_internal.h header containing function prototypes
• Move robust predicates to separate source file
• Move file I/O routines to separate source file
• Remove most exit(1) calls and return error codes instead
• Remove unused members from mesh and behavior structs
• Add experimental support for x64 compilation
• Include aCute for quality mesh generation

Changes to aCute:

• Introduction of memory pool
• Cleanup and minor fixes

Please refer to the commit history if you need a complete changelog.

Please note that although both Triangle and aCute are freely available to researchers, they may not be sold or included in commercial products without a license. Make sure to take a look at the original README included in the Triangle source dir.