[Gmsh] To mesh or not to mesh.

Christophe Geuzaine cgeuzaine at ulg.ac.be
Thu Mar 8 10:54:50 CET 2007

Cécile Giorla wrote:
> Hi,
> My problem is a little more complicated in fact. The small hole volume 
> has to be once defined, since I define it with the extrude command (see 
> the geo file). Maybe I do not well define the volume. Since I extrude 
> the volume, I don't well know the number of the faces created, so I can 
> not define a surface loop. I could do it by clicking with the mouse on 
> them, but I need to be able to do it a automatic way because at the end, 
> I want to generate he geo file with an exterior script.
> Thank you.

Solution 1: just delete the volume, i.e.,

tmp[] = Extrude {0,0,1} {
Delete { Volume{tmp[1]}; }

// tmp[0] contains the id of the new "top" extruded surface
// tmp[1] contains the id of the new extruded volume

Solution 2: like Jacques said, mesh everything, but only save the parts 
you need using physical groups.

> Cecile Giorla.
> Christophe Geuzaine a écrit :
>> Cécile Giorla wrote:
>>> Hi!
>>> I have defined a volume as beeing a big volume with an volume's hole 
>>> inside, this is OK. Next, I want to mesh only this volume, and not 
>>> the hole inside. But as my hole is defined as a volume, it seems to 
>>> be meshed anyway. Is there an option to tell GMSH not to mesh this 
>>> hole volume?
>>> Thank you.
>> Hi Cecile - just don't define the small volume inside: the definition 
>> of the big volume outside only relies on a "surface loop" for the 
>> hole--not the definition of a volume. See the attached example.

Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science