Mesh generation¶

This section presents tutorials for using mmg2d for mesh generation from a set of points or a set of edges.

Mesh generation from a set of edges¶

This first example shows how to generate a mesh from a set of edges. The input data (acdcBdy.mesh) is displayed below:

../_images/acdcEdg.png — Initial set of edges¶

To generate a mesh containing these edges, run mmg2d with the input mesh name as a argument. In order to prevent the font from being smoothed out, specify a sharp angle detection of 10 degrees using the -ar option. Sharp angles will be considered as a geometric property of the mesh and hence will be preserved:

mmg2d_O3 -ar 10 acdcBdy.mesh

The output mesh acdcBdy.o.mesh is displayed below:

../_images/acdcNoHmax.png — Generated mesh with a sharp angle detection of 10 degrees¶

Note that mmg creates a mesh for all the internal subdomains created by the edges, including the holes in the letters A and D. By default, all subdomains are saved in the output mesh file. It is possible to choose to keep only one subdomain using the -nsd option. For instance, the following command will only keep the letter D (domain number 6) as the output mesh:

mmg2d_O3 -ar 10 -nsd 6 acdcBdy.mesh

../_images/acdc-nsd.png — Generated mesh with only one sub-domain¶

Finer mesh generation¶

To generate a finer mesh, it is possible to specify a maximal edge size value using the -hmax option. In this example, since the bounding box size of the mesh is 500x200, we can impose a maximal edge size of 10 by running the following command:

mmg2d_O3 -ar 10 -hmax 10 acdcBdy.mesh

../_images/acdcMesh.png — Generated mesh for a maximal edge size of 10 (without unwanted subdomains)¶

Mesh generation from a set of points¶

In this example, let us take a look at mesh generation from a set of points. The initial mesh (square.mesh) is represented below.

../_images/initPoints.png — Initial set of points¶

To generate a mesh of the convex hull of these points, run mmg2d:

mmg2d_O3 square.mesh

The output mesh square.o.mesh is represented below:

../_images/squareDefault.png — Generated mesh from a set of points¶

In this execution of mmg, a mesh containing all the initial vertices has been created first. Then, the mesh has been optimized by a standard adaptation procedure. Since no option or size map have been provided, mmg attempts to produce a high-quality mesh with a minimal number of vertices.

Preservation of the initial points¶

To keep the initial points, run mmg using the -noinsert, -noswap and -nomove options in order to deactivate all remeshing operations and only perform the mesh generation phase:

mmg2d_O3 square.mesh -noinsert -nomove -noswap

../_images/squareNoinsert.png — Generation of a mesh with preservation of initial points¶