# [Gmsh] Transfinite Surfaces

**Christophe Geuzaine**
cag32 at case.edu

*Fri Nov 3 04:40:57 CET 2006*

Laurent CHAMPANEY wrote:
>* Hi,
*>*
*>* I want to use Transfinite Surfaces on faces of NON Transfinite Volumes
*>* in order to prescribe the geometry of the mesh on faces that will be
*>* later connected to other meshes.
*>*
*>* The 2D mesh is correct, but in some situations, some nodes are added on
*>* the transfinite surface (which is not transfinite any more...) during
*>* the construction of the 3D mesh. Is this possible or is it a bug in gmsh?
*>*
*
It's a known (mathematical) limitation of the 3D Delaunay algorithm. You
could use the Delaunay+Frontal approach of the Netgen algorithm to solve
this problem.
(Beware that in version 1.65 using the Netgen algorithm is a bit
tedious, as you need to make sure, by hand, that all the surfaces in a
"surface loop" are oriented with their normals pointing outside of the
volume they bound. Gmsh 2.0 will fix this problem: all the orientations
in the new version are performed automatically.)
>* Thanks
*>* Laurent
*>*
*
--
Christophe Geuzaine
Assistant Professor, Case Western Reserve University, Mathematics
http://www.case.edu/artsci/math/geuzaine