# [Gmsh] All-quad unstructured 2D - possible?

Christophe Geuzaine cgeuzaine at ulg.ac.be
Wed Mar 17 21:13:53 CET 2010

```On 17/03/10 19:04, Umut Tabak wrote:
> Hugh Blackburn wrote:
>> Maybe I'm missing the point here (as a total noob I would not be
>> surprised if this were the case) but if I just mesh what you sent in
>> Mesh/2D I get a mixture of quads and tris. Screen grab attached. If I
>> look in the file you sent it says
>>
>> Mesh.SubdivisionAlgorithm=2;
> This thread also was interesting for me.
>
> If you check the file there are some comments, actually the 2 option is
> for all hexas as mentioned there, if you use option 1 that is what you
> want to get even if there are some error messages.
>

lc = 0.1;
lca = 0.01;
Point(1) = {0, -1.0, 0, lc} ;
Point(2) = {-1.0, 0, 0, lc} ;
Point(3) = {0, 1.0, 0, lc} ;
Point(4) = {1.0, 0, 0, lc} ;
Point(5) = {0, 0, 0, lca} ;
Point(6) = {0.25, 0.01, 0, lca} ;
Point(7) = {0.5, 0, 0, lca} ;
Point(8) = {0.325, 0.075, 0, lca} ;
Circle (303) = {1, 5, 2 };
Circle (304) = {2, 5, 3 };
Circle (305) = {3, 5, 4 };
Circle (306) = {4, 5, 1 };
Spline(101) = {6, 7, 8, 5, 6};
Line Loop(5) = {303,304,305,306} ;
Line Loop(6) = {101} ;
Plane Surface(9) = {5,6} ;
Recombine Surface{9};
Mesh.SubdivisionAlgorithm=1;

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--
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine

```