[Gmsh] FW: from hexahedrons to tetrahedrons

[julien hoessler]

I think it is supposed to be 6 tets: 3 successive rectangle to  
triangle mappings
see the attached mesh:
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Regards
Julien
On 20 May 2011, at 13:39, Smith, Mark wrote:

> I think 5 tets in a cube see attached.
> mark
>
> -----Original Message-----
> From: gmsh-bounces at ace20.montefiore.ulg.ac.be [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be 
> ] On Behalf Of Geordie McBain
> Sent: 20 May 2011 03:05
> To: Michel Dupront
> Cc: gmsh at geuz.org
> Subject: Re: [Gmsh] from hexahedrons to tetrahedrons
>
>> I have a structured mesh with hexahedrons and I would like to split
>> each hexahedrons into tetrahedrons.
>> Is it possible ?
>
> Hello.  Someone asked me this the other day.  At first I thought it  
> should be easy, but then I found I didn't know how to do it, in Gmsh  
> or otherwise.  I had thought that one should be able to simply split  
> each hexahedron, but then reading the documentation for how it's  
> done in the VTK library:
>
>  http://www.vtk.org/doc/nightly/html/ 
> classvtkDataSetTriangleFilter.html
>
> I saw that one must meet `the issue of face compatibility across  
> quadrilateral faces (which way to orient the diagonal?)'.
>
> I figure then that it should be possible to export a hexahedral mesh  
> as VTK, use this VTK function to split to tetrahedra and save as  
> VTK, then reread the VTK.  I haven't actually gone on to try this.
>
> I would be interested to hear of a pure Gmsh solution, if anyone has  
> one.
>
>> if yes into how many tetrahedrons ?
>
> I think the answer for this should be six, since the volume of a  
> tetrahedron with three mutually perpendicular edges of unit length  
> is 1/6.
>
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Julien Hoessler
PhD Student
Department of Aeronautics
Imperial College London

Phone: +44 (0) 20759 45042
Mobile: +44 (0) 78343 80977
Email:   julien.hoessler06 at imperial.ac.uk