[Gmsh] Periodic Surface

[Christophe Geuzaine]

On 28 Dec 2011, at 05:40, Mikhail Artemiev wrote:

> Hi all!
> I try to mesh a cube in such a manner that the opposite
> faces have identical mesh.
> For this purpose I try to use 'Periodic Surface'.
> This is my script:
> 
> // --- the cube ---
> cl = 0.2;
> Point(1) = {0, 0, 0, cl};
> Point(2) = {1, 0, 0, cl};
> Line(1) = {1, 2};
> outSurf[] = Extrude{0, 1, 0}{Line{1};};
> outVol[] = Extrude{0, 0, 1}{Surface{outSurf[1]};};
> 
> // --- the periodicity ---
> // only x = 0 and x = 1 faces for example
> surfMaster = outVol[5]; // x = 0
> surfSlave = outVol[3]; // x = 1
> boundMaster[] = Boundary{Surface{surfMaster};};
> boundSlave[] = Boundary{Surface{surfSlave};};
> Periodic Surface surfSlave { boundSlave[] } = surfMaster { boundMaster[] };
> 
> If one will look at (x=1)face in +X view and at (x=0)face in -X view, the meshes will identical.
> But I think that it is incorrect.
> Because one should look at one, say +X, view.
> To look the mesh on the (x=0)face in +X view, I used a clipping (A=-1, B=C=0).
> In this case the meshes was not identical, but they was not really different too.
> It seemed that (x=1)face was a mirror reflection of the (x=0)face.
> Then I printed boundMaster and boundSlave arrays, and I realized that in +X view
> boundMaster had the edges in clockwise, boundSlave - in counterclockwise.
> After that I changed these arrays by hand:
> 
> boundMaster[] = {3, 21, 10, -12}; // counterclockwise
> boundSlave[] = {4, 17, -8, -13}; // counterclockwise
> 
> After that Gmsh built an ugly mesh.
> I tried with 2.5.0 and 2.5.1 (from nightly sources) versions with the same result.
> OS - Windows.
> 
> Is still 'Periodic Surface' an experimental feature?
> Or I use it incorrectly?
> 

Hi Mikhail - The feature is still buggy. We are working on improving it.

Christophe
 

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