[Gmsh] High-order quads

Martin Vymazal martin.vymazal at vki.ac.be
Wed Mar 16 00:22:08 CET 2011


Hi Geordie,

  thank you very much.

  Best regards,

   Martin


Quoting Geordie McBain <gdmcbain at freeshell.org>:

> 2011/3/16 Martin Vymazal <martin.vymazal at vki.ac.be>:
>> Hello,
>>
>>  could someone please tell me what is the local node numbering for P3
>> quadrilaterals in gmsh? Looking in the documentation, it seems that P3 quads
>> are not supported, but using "-order 3" I still can generate a mesh with
>> elements which look like this:
>>
>>           x---x---x---x
>>           |           |
>>           x   x   x   x
>>           |           |
>>           x   x   x   x
>>           |           |
>>           x---x---x---x
>>
>>  Can you please tell me what are the local node numbers?
>
> Hello.  I found this ASCII diagram in a C comment on lines 317--332 of
> Geo/MQuadrangle.h.
>
> /*
>  * MQuadrangle
>  *
>  *   3--3+3E-...--4+2E--2
>  *   |                  |    E = order - 1;
>  *   |                  |    N = total number of vertices
>  * 4+3E                3+2E
>  *   |                  |    Interior vertex numbers
>  *  ...  4+4e to N-1   ...    for edge 0 <= i <= 3: 4+i*E to 3+(i+1)*E
>  *   |                  |     in volume           : 4+4*E to N-1
>  * 3+4E                4+E
>  *   |                  |
>  *   |                  |
>  *   0---4--...---3+E---1
>  *
>  */
>
> I think it should specialize to the case you want for E=2, so that,
> for example, along the bottom we'd have 0, 4, 5, 1.
>



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