[Gmsh] Meshing an ellipse with quadrilaterals - forces program to quit

[Christophe Geuzaine]

On 13 Dec 2013, at 07:48, Arne Muecke <arne.muecke at gmail.com> wrote:

> Hello
> first of all, I am new to GMSH and still in the beginnings of my learning process.
> What I want to do is creating an ellipse (2d) and mesh it with quadrilaterals (4 nodes). 
> 
> I had success creating the ellipse geometry as followed:
> -------------------------------------------------------------------- beginning of the file -------------------------------------
> //mesh characteristic length
> cl = 0.5;
> 
> Point(1) = {0,0,0,cl};
> 
> Point(2) = {10,0,0,cl};
> 
> Point(3) = {-1.4142,0,0,cl};
> 
> Point(4) = {1.4142,0,0,cl};
> 
> Point(10) = {0,0.7071,0,cl};
> 
> Point(20) = {0,-0.7071,0,cl};
> 
> Ellipsis(5) = {10,1,2,3};
> 
> Ellipsis(6) = {4,1,2,10};
> 
> Ellipsis(7) = {20,1,2,3};
> 
> Ellipsis(8) = {4,1,2,20};
> 
> Line Loop(9)={5,6,7,8};
> 
> Plane Surface(11)={9};
> 

As the error message says: line loop 9 is wrong. You need to change it to:

Line Loop(9) = {5, -7, -8, 6};
Plane Surface(11) = {9};




> //Boundaries
> Physical Line(12)={5};
> Physical Line(13)={6};
> Physical Line(14)={7};
> Physical Line(15)={8};
> 
> Physical Surface(21)={11};
> 
> -------------------------------------------------------------end of file--------------------------
> 
> So with this .geo file, I start GMSH. When I am trying to create the 2D Mesh, the program just crashes. For reference, I attached the log file. <log.rtf>
> 
> When I set the value "cl" to 1 in the File, GMSH will create one element. It doesn't matter if I am using Triangles or Quadrilaterals. 
> 
> I would really appreciate if somebody could help me and tell what I am doing wrong.
> 
> Thank you and regards
> Arne
> 
> 
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine