[Gmsh] Entity numbering

[Christophe Geuzaine]

David Andrs wrote:
> Hi!
> 
> We are using gmsh for post-processing purposes in our hp-FEM code hermes3d.
> 
> We number all mesh entities (elements, vertices, edges, faces) from zero 
> and we have the following problem with gmsh:
> 
> - We list the vertices in the $Nodes section, starting from 0, but the 
> vertex with the zeroth index is shown as 1.
> 
> - The same behavior with elements and $Elements section. If we use more 
> $Elements sections, than the zeroth entity is display with two, three, 
> etc. So it seems that the 0 has some special meaning (some sort of auto 
> increment?)
> 
> The file with the mesh for testing can be found on 
> http://spilka.math.unr.edu/~andrsd/ref.msh
> 
> Is there a possibility to turn off this auto-increment option and have 
> the entities numbered from 0? If not, could you consider implementing 
> such a feature?

Unfortunately, no: we use "0" as a special index. Cf. the documentation:

@var{node-number} is the number (index) of the @var{n}-th node in the 
mesh; @var{node-number} must be a postive (non-zero) integer. Note that 
the @var{node-number}s do not necessarily have to form a dense nor an 
ordered sequence.




> 
> The gmsh we are using is 2.2.5.
> 
> Thanks,
> --
> David Andrs
> 
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> 


-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine