# [Gmsh] Query on GMSH

David Colignon David.Colignon at ulg.ac.be
Fri Jul 16 13:47:24 CEST 2010

```Hi,

from the manual:

http://www.geuz.org/gmsh/doc/texinfo/gmsh.html#Mesh

...
...
In this process, the mesh of an entity is only constrained by the mesh of its boundary. For example, in three
dimensions, the triangles discretizing a surface will be forced to be faces of tetrahedra in the final 3D mesh only if
the surface is part of the boundary of a volume; the line elements discretizing a curve will be forced to be edges of
tetrahedra in the final 3D mesh only if the curve is part of the boundary of a surface, itself part of the boundary of a
volume; a single node discretizing a point in the middle of a volume will be forced to be a vertex of one of the
tetrahedra in the final 3D mesh only if this point is connected to a curve, itself part of the boundary of a surface,
itself part of the boundary of a volume. This automatically assures the conformity of the mesh when, for example, two
surfaces share a common line. But this also implies that the discretization of an “isolated” (n-1)-th dimensional entity
inside an n-th dimensional entity does not constrain the n-th dimensional mesh—unless it is explicitly told to do so
(see Miscellaneous mesh commands). Every meshing step is constrained by the characteristic length field, which can be
uniform, specified by characteristic lengths associated with points in the geometry, or defined by general “fields” (a
scalar field defined on another mesh using post-processing view, threshold fields associated with point or line
“attractors”, etc.).
...
...

http://www.geuz.org/gmsh/doc/texinfo/gmsh.html#Miscellaneous-mesh-commands

Point | Line { expression-list } In Surface { expression };
Embed the point(s) or line(s) in the given surface. The surface mesh will conform to the mesh of the point(s) or
lines(s). Note that embedded lines only work with the MeshAdapt 2-D algorithm.

and from the archive of the mailing list:

http://www.geuz.org/pipermail/gmsh/2009/004912.html

Regards,

Dave

--
David Colignon, Ph.D.
Collaborateur Logistique du F.R.S.-FNRS
CÉCI - Consortium des Équipements de Calcul Intensif
ACE - Applied & Computational Electromagnetics
Sart-Tilman B28
Université de Liège
4000 Liège - BELGIQUE
Tél: +32 (0)4 366 37 32
Fax: +32 (0)4 366 29 10
WWW:    http://hpc.montefiore.ulg.ac.be/

On 16/07/10 11:36, Sanyal Sebanti wrote:
> Hi,
> We are using GMSH software for developing our finite element models.
>
> We are working with 3D geometries ( e.g. a cylinder).
> In a .geo file , I specified the cylinder geometry and some arbitrary points inside this cylinder.
> When I created the tetrahedral mesh, I found  that these arbitrary points are not the vertices of the tetrahedra.
> Is there a way that I can force these points to become the vertices of the tetrahedra?