# [Gmsh] 2D meshing pecularities

**Christophe Geuzaine**
geuzaine at acm.caltech.edu

*Tue Mar 5 01:27:43 CET 2002*

Christophe Geuzaine wrote:
>*
*>* "Pascal A. Dupuis" wrote:
*>* >
*>* > Hello,
*>* >
*>* > I am trying to nail down a 2D meshing problem; here is a minimal test case.
*>* > I have a geometry mostly done of half cyliders. To verify the design coherency,
*>* > I regulary generate a 2D meshing: in this case, most are 'ruled surface'
*>* > delimited by two lines and two half circles. As it appears, the intermediate
*>* > points generated on the ruled surface are incorrect and seems to fall outside
*>* > the surface. The following commands illustrate this behaviour:
*>*
*>* Yes, this is normal (!). You cannot define surfaces for which the plane
*>* projection is degenerate (cf. FAQ 5.2). In your case, you should not use
*>* half circles, but only arcs having an angle smaller than 2*Pi.
* ^^^^^^^^^^^^^^^^^
You should read "smaller than Pi", of course.
Christophe
--
Christophe Geuzaine
Tel: (626) 395-4552 http://www.geuz.org
Fax: (626) 578-0124 mailto:geuzaine at acm.caltech.edu