if you want to test with your own meshes,
you before must ensure that the mesh contains :
. only triangular 3dfaces,
. with p13=p10 ,
. that in each 3dface there are no more than 1 segment (p13 p10) of zero length,
. and that the direction of the list of points is always counterclockwise,
. i.e. that the zeta component of the normal to the face is positive