How to save boundary triangle and its attributs

Dear sir:
The mesh saved by mmg3d doesn’t include infors about boundary . How to save boundary triangle and its attributes.


Mmg saves informations related to “boundary” triangles. For Mmg, a triangle is boundary if:

  • it belongs to 1 tetra only (which means that this triangle is along the external boundary of the mesh);
  • it belongs to 2 tetra with different references (= color). (so the triangle is at the interface of 2 different domains);

But for now, Mmg doesn’t save the whole list of triangles defined by the tetrahedra connectivity (internal triangles): is it what you needs?



Hello, just chiming in here, that explains my problem-confusion as well. I’ve had great success with Mmg (thanks!) but was confused couldn’t find the internal boundaries triangles.

I too would very much like to ask if this can be done or will be possible in the future. It’s critical to my workflow.

Thanks and best,


I have recently added in the develop branch the possiblity to get the internal edges of a 2D mesh using the following API functions in mmg2d:

int MMG2D_Get_numberOfNonBdyEdges(MMG5_pMesh mesh, int* nb_edges)
int MMG2D_Get_nonBdyEdge(MMG5_pMesh mesh, int* e0, int* e1, int* ref, int idx) 
// e0 = index of "left" point of the edge
// e1 = index of "right" point of the edge
// ref = color/tag/reference of the edge,
// idx = index of the edge (between 1 and nb_edges)

I will try to add similar APIs for MMG3D before the next release (Decembre), but it will very probably be a ß-feature because I will not have time to test more than very basic tests.


Fantastic thank you. I have a related question but will open a new thread for that.


I don’t see this new thread: did you delete it?