[Gmsh] Extrude command and element numbering

[Christophe Geuzaine]

Kuldeep Amarnath wrote:
> 
> Hi
>    The syntax for the 'Extrude' supposedly allows for user numbering of the
> elements created. Eg. (from tutorial 't3.geo':
> 
> Extrude Surface { 6, {0,0,h} } {
>   Layers { {8,4,2,1}, {9000:9003}, {0.25,0.5,0.75,1} } ;
> } ;
> 
> The above command should number the four new volume elements from 9000 to
> 9003. However in practice this does not seem to happen! The new elements are
> numbered arbitrarily by Gmsh irrespective of what I specify. Is this a bug?
> or am I doing something wrong?

The numbers specified in the extrusion command refer to number of the
geometrical volumes (not the elements: there can be many elements in one
volume) that the extrusion creates. In the case of an unstructured mesh,
you would define these volumes by hand, with the 'Surface Loop' and the
'Volume' commands. 

In your example, you can use the numbers of the "automatically created"
volumes 9000, 9001, 9002 and 9003 in any subsequent Physical Volume
definition, as in "Physical Volume(101) = {9000:9004};".

Actually, in Gmsh, you can never control the individual numbering of
nodes or elements. You can only control the numbering of the entities
(elementary of physical) to which they belong.


Christophe

-- 
Christophe Geuzaine

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