[Gmsh] Normal vector orientation?

[Christophe Geuzaine]

Kaveh Ghayour wrote:
> Hi,
> 
> I have a convex plane curve, defined by its vertices
> in counter-clockwise order. I extrude this plane
> surface (translate it along some given directon) and
> obtain a volume.  When I try to surface mesh the
> resulting volume, my normals on the original surface
> point outwards, but on the lower surface and the side
> surfaces point inwards.
> 
> I do not get any error or warning messages.  Is this a
> bug or am I doing something wrong? 

Hi Kaveh - It's not a bug and you're not doing anything wrong :-) It's
just a choice that the extrusion routine makes (a surface can belong to 
two extruded entities, so the orientation has to be inwards for
one extruded entity and outwards for the other).

We should probably use outward orientations by default when there is
only one extruded entity, though. I might change it in a future release.

Best,

Christophe

-- 
Christophe Geuzaine
Applied and Computational Mathematics, Caltech
geuzaine at acm.caltech.edu - http://geuz.org