[Gmsh] Error in MED format output

Yvan FOURNIER yvan.fournier at edf.fr
Tue Sep 22 11:50:40 CEST 2009


Hello,

I would like to report 2 issues with MED output format (in Gmsh 2.4.2 and 
all older versions I have tested)

- elements are not oriented correctly, meaning they probably do not follow 
the MED element numbering conventions.

- Families in MED files do not contain groups or attributes (attributes 
should be deprecated soon, so groups are best).

In GModel_IO_MED.cpp, we have  of the following form:

if(MEDfamCr(fid, meshName, (char*)familyName.c_str(), 
            (med_int)num, 0, 0, 0, 0, (char*)groupName.c_str(),
            (med_int)entities[i]->physicals.size()) < 0)

The last argument of MEDfamCr should be the number of associated groups, 
which is always 1
if families are mapped 1-to-1 with physical entities, so I beleive the 
call should be :

if(MEDfamCr(fid, meshName, (char*)familyName.c_str(), 
            (med_int)num, 0, 0, 0, 0, (char*)groupName.c_str(),
            (med_int)entities[i]->physicals.size()) > 0)


(i.e. the sign is wrong in the test for the original version).

Normally, even if entities[i]->physicals.size() == 0, Families should 
contain a group, so
maybe another wy of defining the group should be sued in this case, and 
the call
would simply be :

if(MEDfamCr(fid, meshName, (char*)familyName.c_str(), 
            (med_int)num, 0, 0, 0, 0, (char*)groupName.c_str(), 1)

I have not tested the patch or built a complete GMSH compilation 
environment,
but I beleive this could fix the second bug (i.e. missing group 
definitons) with MED output.

I may try to look into element node numbering for the first bug in the 
future, but
this may have to wait a bit.

Best regards,

        Yvan Fournier
        EDF R&D
        Fluid Dynamcis, Power Generation, and Environment
        6 quai Watier - BP 49
        78401 Chatou Cedex
        FRANCE






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