# Question on your demo file

Makky S. Jaya jaya at iag.uni-stuttgart.de
Tue Mar 21 10:59:59 CET 2000

```Dear Christope,

I am learning and probing now the demo files for GMSH.
Unfortunately, I have still two questions concerning
the utilization of defining physical {surface,line or
point}.

1.
As an example I take the file 'ex04.geo'. Herewith are
two planes created. After using 'mesh-1d->>2d' I have
the mesh. All surfaces in which the boundary points were
defined are meshed, including the surface (22). In fact,
one would supress the creating mesh from surface (22),
in order to have a hole.

Q: How can I supress a mesh created on a certain surface?

| Line Loop(21) = {17,-15,18,19,-20,16};
| Plane Surface(22) = {21};
|
| /* README: This surface is made of two line loops, i.e. has one hole */
|
| Line Loop(23) = {11,-12,13,14,1,2,-3,4,5,6,7,-8,9,10};
| Plane Surface(24) = {23,21};

2.
Still consider 'ex04.geo'. Until the last line above, two
planar surfaces were created. After defining boundary lines with
'physical->add->line' for these two surfaces, I would define
physical surface with 'physical->add->surface' in order to close
the meshing procedure. At this stage, I was not succeeded.
The result was that I do not have the definition of (triangle)
element if I save the last procedure above. Only element type 1
(line) was saved by the program.

Q: How can I use the function 'physical->add->surface'?

Thank's a lot for the answer.

My best regards,
Makky

```