[Gmsh] Problem to define correctly triangular facets to make a volume

[Jerier Jean-François]

Hi all,

 I have a triangular mesh (facets) performed from the matlab function "tri".
I export this facets on Gmsh via my Matlab routine in order to define a volume.

It seems that some facets are not correctly defined or well oriented because I cannot make my volume.
I look at a simple geo file from Gmsh and I don't understand the principle or the logic to well oriented the facets.

Usually, the facet is defined in relation to its normal vector (i.e., clockwise or counter-clockwise). 
>From the following figure, can you explain me how do I must define each facet or triangle ?


3------6------9
| \ T2 | \ T4  |
|   \     |   \     |
|     \   |     \   |
| T1 \ | T3 \ |
2------5------8
| \ T6 | \ T7  |
|   \     |   \     |
|     \   |     \   |
| T5 \ | T8 \ |
1------4------7

1 - 2 - ... - 9 = nodes
T1 - T2 - .... - T8 = triangles


In matlab, each facet is defined in the counter-clockwise. In Gmsh, I didn't manage to define a rule.

Please, can you give me more explanations on this subject ?


Regards
JF