[Dune] Usage of "BoundaryDomain" or "BoundarySegment" for surface meshes

[Sacconi, Andrea]

Hi DUNErs,

I would like to ask you a quick question about how to specify the boundary of your mesh in a DGF file.
I'm dealing with surface meshes, so for example a collection of triangles in R^3. I tried to prescribe the boundaries using BOUNDARYDOMAIN or BOUNDARYSEGMENT, as I always do, but now it doesn't work.
I always get the boundaryId equal to 1, the default value. Why?
The file I am using sounds like the following. It's a sort of "pyramid", without the flat base. So four elements and five vertices, with 2 and 3 as boundary labels. Where am I wrong?

DGF
% Elements = 4  |  Vertices = 5

VERTEX

-1.0 -1.0 0.0
1.0 -1.0 0.0
1.0 1.0 0.0
-1.0 1.0 0.0
-0.975 0.0 2.0
#

SIMPLEX
0 1 4
1 4 2
2 4 3
3 4 0
#

BOUNDARYSEGMENTS
2        0 1
2        2 3
3        1 2
3        0 3
#

GRIDPARAMETER
#

__________________________________________________________

Andrea Sacconi
PhD student, Applied Mathematics
AMMP Section, Department of Mathematics, Imperial College London,
London SW7 2AZ, UK
a.sacconi11 at imperial.ac.uk