[Gmsh] [Freefempp] Import a 2D mesh

[Geordie McBain]

On Thu, Sep 3, 2009 at 5:56 AM, Christophe Geuzaine<cgeuzaine at ulg.ac.be> wrote:
> Indeed, that should be easy. Currently we only save "Triangles",
> "Quadrilaterals" and "Tetrahedra" in the MESH format. Is the format for the
> edges similar? (What is the label?)

>From Frey (2001, p. 33, Section 7.2.1 `The mesh format', which I take
to be the specification), the Edges block does look very much like the
Vertices, Triangles, Quadrilaterals, and Tetrahedra blocks, viz.:

%<---
Edges
<n>
<e11> <e21> <ref1>
<e12> <e22> <ref2>
...
<e1n> <e2n> <refn>
%<---

where <n> is the number of edges, <e1i> and <e2i> are the identifiers
of the terminal vertices of the i-th edge, and refi is its reference
label.  (I suppose ultimately the latter should be the identifier of
the Physical Line, but for present consistency with the triangles it
should probably be the identifier of the elementary geometric identity
- this was discussed 31 July  - 17 Aug. on the Gmsh list in the thread
`New Mesh.BdfElementPID Option'.)

Reference:

Frey, P. J. (2001). MEDIT: An interactive mesh visualization software.
Technical Report 253, INRIA, Rocquencourt.
(PDF freely available from http://hal.inria.fr/inria-00069921/fr.)