3.1.3 Mesh Generation Software

In this section, a selection of volumetric mesh generation software tools is presented. An overview is given in Table 3.1.

Table 3.1: Overview of the meshing software presented in this work

	License	Element Types	Input Geometry
CGAL	GPL,LGPL	Tri,Tet	oracle$^\star$
CUBIT	commercial	Tri,Tet,Quad,Hex	IGES,STEP,STL
Gmsh	GPL	Tri,Tet	IGES,STEP,STL
MeshGems	commercial	Tri,Tet,Quad,Hex,Mixed	IGES,STEP,STL
Netgen	LGPL	Tri,Tet	CSG,STEP,STL
Pointwise	commercial	Tri,Tet,Quad,Hex,Mixed	CSG,IGES,STEP,STL
Tetgen	X11/MIT	Tet	PLC
Triangle	commercial,GPL-like	Tri	PLC
ViennaMesh	GPL	Tri,Tet	CSG,PLC,STEP,STL

The GNU general public license (GPL) [6], the GNU lesser general public license (LGPL) [6], and the X11/MIT license [16] are free open source licenses. The listed element types are triangles (Tri), tetrahedrons (Tet), quadrilaterals (Quad), hexahedrons (Hex), and mixed element types (Mixed). More information on the input geometry formats can be found in Section 2.1. $^\star$ CGAL itself is a software library rather than a software tool and uses a generic mechanism called oracle to specify the geometry. Oracle implementations for polyhedrons, implicit functions and 3D images are provided by CGAL.

The Computational Geometry Algorithms Library (CGAL) [2] is a free open source library. Among the rich set of provided geometric algorithms, CGAL offers incremental Delaunay meshing algorithms for two- and three-dimensional geometries. A peculiarity of CGAL is the generic software design which significantly increases flexibility [36].

CUBIT [15] is a commercial mesh generation tool developed at the Sandia National Laboratories. It supports a wide range of different mesh generation algorithms with a focus on quadrilateral and hexahedral mesh generation.

Gmsh [5][35] is a free open source meshing framework providing a couple of meshing algorithms such as structured and unstructured mesh generation of two- and three-dimensional meshes. Gmsh uses other free open source meshing tools and combines these with pre- and post-processing steps. Unlike other meshing applications, Gmsh also includes a scripting language for controlling the meshing process.

MeshGems [7] is a commercial mesh generation software which supports triangular and quadrilateral surface mesh generation as well as tetrahedral, hexahedral, and mixed volumetric mesh generation. Additionally, the tool offers multiple algorithms for CAD geometry enhancement and error cleaning.

Netgen [9][130] is a free open source tetrahedral advancing front mesh generation tool with support for CSG and triangular hull mesh input geometries. Additional post-processing steps ensure the Delaunay property of the resulting meshes.

Pointwise [10] is a commercial mesh generation software supporting a wide range of CAD input geometries. It is capable of generating simplex, quadrilateral, hexahedral, and mixed element meshes.

Tetgen [14][53] is a free open source 3D incremental Delaunay mesh generation software with support for multiple regions. The tool uses PLCs as input geometries and is related to Triangle as the algorithms, the concepts, and the programming interface are very similar.

Triangle [17][64] is a very popular and widespread free open source 2D incremental Delaunay mesh generation software tool.

ViennaMesh [19][49] is a flexible free open source meshing framework based on a module approach. Besides providing a unified interface to several external meshing tools, it also provides additional mesh adaptation algorithms via an extensible platform.