# gf_mesh¶

**Synopsis**

```
M = gf_mesh('empty', int dim)
M = gf_mesh('cartesian', vec X[, vec Y[, vec Z,..]])
M = gf_mesh('pyramidal', vec X[, vec Y[, vec Z,..]])
M = gf_mesh('cartesian Q1', vec X, vec Y[, vec Z,..])
M = gf_mesh('triangles grid', vec X, vec Y)
M = gf_mesh('regular simplices', vec X[, vec Y[, vec Z,...]]['degree', int k]['noised'])
M = gf_mesh('curved', mesh m, vec F)
M = gf_mesh('prismatic', mesh m, int nl[, int degree])
M = gf_mesh('pt2D', mat P, imat T[, int n])
M = gf_mesh('ptND', mat P, imat T)
M = gf_mesh('load', string filename)
M = gf_mesh('from string', string s)
M = gf_mesh('import', string format, string filename)
M = gf_mesh('clone', mesh m2)
M = gf_mesh('generate', mesher_object mo, scalar h[, int K = 1[, mat vertices]])
```

**Description :**

General constructor for mesh objects.

This object is able to store any element in any dimension even if you mix elements with different dimensions.

Note that for recent (> 6.0) versions of matlab, you should replace the calls to ‘gf_mesh’ with ‘gfMesh’ (this will instruct Matlab to consider the getfem mesh as a regular matlab object that can be manipulated with get() and set() methods).

**Command list :**

`M = gf_mesh('empty', int dim)`

Create a new empty mesh.

`M = gf_mesh('cartesian', vec X[, vec Y[, vec Z,..]])`

Build quickly a regular mesh of quadrangles, cubes, etc.

`M = gf_mesh('pyramidal', vec X[, vec Y[, vec Z,..]])`

Build quickly a regular mesh of pyramids, etc.

`M = gf_mesh('cartesian Q1', vec X, vec Y[, vec Z,..])`

Build quickly a regular mesh of quadrangles, cubes, etc. with Q1 elements.

`M = gf_mesh('triangles grid', vec X, vec Y)`

Build quickly a regular mesh of triangles.

This is a very limited and somehow deprecated function (See also

`gf_mesh('ptND')`

,`gf_mesh('regular simplices')`

and`gf_mesh('cartesian')`

).

`M = gf_mesh('regular simplices', vec X[, vec Y[, vec Z,...]]['degree', int k]['noised'])`

Mesh a n-dimensional parallelepiped with simplices (triangles, tetrahedrons etc) .

The optional degree may be used to build meshes with non linear geometric transformations.

`M = gf_mesh('curved', mesh m, vec F)`

Build a curved (n+1)-dimensions mesh from a n-dimensions mesh m.

The points of the new mesh have one additional coordinate, given by the vector F. This can be used to obtain meshes for shells. m may be a mesh_fem object, in that case its linked mesh will be used.

`M = gf_mesh('prismatic', mesh m, int nl[, int degree])`

Extrude a prismatic mesh M from a mesh m.

In the additional dimension there are nl layers of elements distributed from

`0`

to`1`

. If the optional parameter degree is provided with a value greater than the default value of`1`

, a non-linear transformation of corresponding degree is considered in the extrusion direction.

`M = gf_mesh('pt2D', mat P, imat T[, int n])`

Build a mesh from a 2D triangulation.

Each column of P contains a point coordinate, and each column of T contains the point indices of a triangle. n is optional and is a zone number. If n is specified then only the zone number n is converted (in that case, T is expected to have 4 rows, the fourth containing these zone numbers).

Can be used to Convert a “pdetool” triangulation exported in variables P and T into a GETFEM mesh.

`M = gf_mesh('ptND', mat P, imat T)`

Build a mesh from a n-dimensional “triangulation”.

Similar function to ‘pt2D’, for building simplexes meshes from a triangulation given in T, and a list of points given in P. The dimension of the mesh will be the number of rows of P, and the dimension of the simplexes will be the number of rows of T.

`M = gf_mesh('load', string filename)`

Load a mesh from a getfem++ ascii mesh file.

See also

`gf_mesh_get(mesh M, 'save', string filename)`

.

`M = gf_mesh('from string', string s)`

Load a mesh from a string description.

For example, a string returned by

`gf_mesh_get(mesh M, 'char')`

.

`M = gf_mesh('import', string format, string filename)`

Import a mesh.

format may be:

- ‘gmsh’ for a mesh created with Gmsh
- ‘gid’ for a mesh created with GiD
- ‘cdb’ for a mesh created with ANSYS
- ‘am_fmt’ for a mesh created with EMC2

`M = gf_mesh('clone', mesh m2)`

Create a copy of a mesh.

`M = gf_mesh('generate', mesher_object mo, scalar h[, int K = 1[, mat vertices]])`

Call the experimental mesher of Getfem on the geometry represented by mo. please control the conformity of the produced mesh. You can help the mesher by adding a priori vertices in the array vertices which should be of size`n x m`

where`n`

n is the dimension of the mesh and`m`

the number of points. h is approximate diameter of the elements. K is the degree of the mesh ( > 1 for curved boundaries). The mesher try to optimize the quality of the elements. This operation may be time consuming. Note that if the mesh generation fails, because of some random procedure used, it can be run again since it will not give necessarily the same result due to random procedures used. The messages send to the console by the mesh generation can be deactivated using gf_util(‘trace level’, 2). More information can be obtained by gf_util(‘trace level’, 4). See`gf_mesher_object`

to manipulate geometric primitives in order to describe the geometry.