# [Gmsh] Quadrangular mesh with flat faces from ruled surface

Felix Salazar felix.a.salazar at gmail.com
Fri Jul 8 17:53:58 CEST 2016

```I don't have a gmsh installation to test. But there is a 2D meshing
algorithm for quads. Delaunay Quad. And you might have to set the recombine
option in the geometry script, before actually meshing anything.

I've done what you need but with transfinite mesh for a structured pattern.

I'll try to get ahold of a GMsh install and run some test.

Good luck
On Jul 8, 2016 5:05 AM, "Julien ERCOLANELLI" <
julien.ercolanelli at ensta-bretagne.org> wrote:

Hi Felix,

Yes a ruled surface that is not flat.

I did what you explained. Recombine + 1 st order

But Gmsh gives non-flat quadrangular mesh elements since the four points of
an element are not in a same plane. All the elements are composed of two
triangles with different normals (see attached file).

Is Gmsh is able to do what I want?

or Do I need a trick to get quadrangular mesh with flat faces? I though
transform my ruled curved surfaces into multiple plane surfaces
approximating my real geometry but it might not be so simple.

------------------------------
*De :* Felix Salazar <felix.a.salazar at gmail.com>
*Envoyé :* jeudi 7 juillet 2016 20:13:38
*À :* Julien ERCOLANELLI
*Cc :* gmsh at onelab.info
*Objet :* Re: [Gmsh] Quadrangular mesh with flat faces from ruled surface

You mean a ruled surface that isn't flat itself?

Recombine the mesh for that surface to get the quads. And pay attention to
specify 1st order elements in the mesh options. If you want structured
quads, check the documentation and the tutorials to get the transfinite
lines and surfaces.

You should get a non-planar surface with flat first order elements.

Hope this helps
On Jul 7, 2016 7:32 AM, "Julien ERCOLANELLI" <
julien.ercolanelli at ensta-bretagne.org> wrote:

Dear Gmsh users,

I am working with ruled surfaces and at the end I would like to get a
quadrangular mesh with only flat faces.

Is there a way to mesh a ruled surface with flat quadrangular faces?

Thanks,

Julien

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