# [Gmsh] Structured mesh

Christophe Geuzaine geuzaine at acm.caltech.edu
Thu Apr 24 17:13:39 CEST 2003

```paul.carrico at free.fr wrote:
> Hi,
>
>
> I would like to make a 3D structured mesh with a simplest object : a cube !
> Following the t6.geo tutorial file, I realised :
>
> 1- a square
> 2- a surface
> 3- an extrusion of the surface
> 4- a volume
> … (basically ! ! !)
>
> 5- Transfinite the lines
> 6- Transfinite the surfaces (and click onto vertices)
> 7- Transfinite the volume (same number as item 4 .. and click onto vertices)
> 8- Then Recombine surface
>
> (… see the result below) !
>
> I only have quadrangle onto the surface but not any hexahedra … what I’m doing
> wrong ? … It’s probably a very basic question but I don’t understand
>
> Just a remark : I’m learning both GMSH and Code ASTER (FEA software) … both GPL
> softwares ! the relationship between the 2 softwares shows that GMSH becomes
> more and more powerfull ! Thank to the GMSH group for it !
>
>
> PC
>
> #################
> #    File cube.geo     #
> #################
> Point(1) = {0,0,0,0.1};
> Point(2) = {1,0,0,0.1};
> Point(3) = {1,1,0,0.1};
> Point(4) = {0,1,0,0.1};
> Line(1) = {2,3};
> Line(2) = {3,4};
> Line(3) = {4,1};
> Line(4) = {1,2};
> Line Loop(5) = {2,3,4,1};
> Plane Surface(6) = {5};
> Extrude Surface {6, {0,0,1}};
> Surface Loop(29) = {15,6,19,23,27,28};
> Volume(30) = {29};
>
> Transfinite Line {9,10,11,8,13,18,22,4,1,3,2,14} = 10;
> Transfinite Surface {19} = {1,10,6,4};
> Transfinite Surface {23} = {14,2,1,10};
> Transfinite Surface {27} = {14,2,3,5};
> Transfinite Surface {15} = {3,5,6,4};
> Transfinite Surface {28} = {6,5,14,10};
> Transfinite Surface {6} = {2,3,4,1};
> Transfinite Volume{30} = {4,6,3,5,1,2,10,14};

The points have to be given in a certain order, so that the elements
inside can be oriented (you cannot generate a "butterfly" pattern; cf.
"Gmsh node ordering" in the doc.)

-> Transfinite Volume{30} = {10,14,5,6,1,2,3,4};

Christophe

--
Christophe Geuzaine

Tel: (626) 395-4552    http://www.geuz.org
Fax: (626) 578-0124    mailto:geuzaine at acm.caltech.edu

```