MMG3D face and edge definitions

#1

Hi all, I am trying to use the MMG3D library, but cannot find the definitions of face and edge of a tet.
i.e. the node numbering for the faces and edges in a tet cell.
where can I find them?
Thx.

Jay

#2

Hi Jay,

Thank you for trying Mmg.

The numbering convention of Mmg is hidden in the Doxygen documentation of the libmmgtypes.h file of the project (the file that contains the description of the Mmg data structures). Normally, you don’t need this information: it is sufficient to give to Mmg the tetra connectivity only (indices of the tetra vertices).

In any case, I will describe first how to use the Doxygen documentation, then I will detail the tetra numbering (so you are not forced to really build the documentation :wink: ).

Doxygen documentation

  1. To build the documentation:
cd mmg
mkdir build
cd build
cmake ..
make doc
  1. to open the mmg3d doc:
firefox doc/mmg3d/html/index.html

Then you will have to navigate to find the libmmgtypes.h doc.

Tetra numbering in Mmg

  • edges are numbered in the order of their extremities indices:

    • edge 0 is the edge with vertices 0 - 1
    • edge 1 is the edge with vertices 0 - 2
    • edge 2 is the edge with vertices 0 - 3
    • edge 3 is the edge with vertices 1 - 2
    • edge 4 is the edge with vertices 1 - 3
    • edge 5 is the edge with vertices 2 - 3

  • A face is numbered with the index of its opposite vertex:

    • face 0 is the face 1 - 2 - 3
    • face 1 is the face 0 - 3 - 2
    • face 2 is the face 0 - 1 - 3
    • face 3 is the face 0 - 2 - 1
  1. illustration
    num
    num.png1670×610 40.8 KB

Regards,

Algiane

1 Like
#3

Hi Algiane, Thanks for your answer, it helps.
BTW, The forum seems down for a half month. but now it is back to normal~good

#4

Hi Jay,

Thank you for this feedback: the discourse server has been upgraded at the beginning of august, I am glad that it is back to normal now!

Regards,
Algiane