Discussion Forum

Dear all,

Playing with my mphtxt exporter, I am asking myself if I came to the right conclusion about the orientation of tetrahedrons.

In order to avoid the "Two elements connect to the same side of the shared element face." error, I started computing volumes (determinants), since the COMSOL_MeshImportExportGuide.pdf file, isn't so stratightforward to me as to define an orientation.

Basically, are all tetrahedrons required to have the same determinant sign?

By that, I mean this: given a tetrahedron t = {v0, v1, v3, v4}, I need all tetrahedrons in the mesh to abide by the sign of

det(t) = Det[{v0 - v1, v0 - v2, v0 - v3}],

with v_i = {p0_i, p1_i, p2_i, p3_i}, pj_i being a point in the 3-dimensional euclidean space. Hence, in case signs differ I will just swap two vertices in a tet and COMSOL will be happy.

Sorry for being so pedantic, I am trying to figure which constraints I must satisfy in order to import meshes into COMSOL.

Thanks for your help! Franco

PS. For reference I am attaching an example mesh and a Mathematica output.