[Gmsh] problem meshing extruded ellipse

[Christophe Geuzaine]

Mark Stock wrote:

> Hello!
> 
> I just installed the gmsh RPM, version gmsh-1.52.1-1, and I seem
> to have a problem with making a triangulated surface mesh of a
> rotationally extruded ellipse. The code is simple:
> 

Yep, our implementation for ellipses is still a little bit shaky. I'm
adding your file to our bug directory and will have a look later.

Best,

Christophe


> [doofus:gmsh]>mo ufo.geo
> Point (1) = {0.,0.,0.,0.01};
> Point (2) = {0.,0.,0.05,0.01};
> Point (3) = {0.,0.5,0.,0.01};
> Point (4) = {0.5,0.,0.,0.01};
> Ellipse (1) = {2, 1, 3, 4};
> Extrude Line {1, {0.,0.,1.}, {0.,0.,1.}, 2.*Pi/3.};
> 
> The 1-D meshing works fine:
> 
> [doofus:gmsh]>gmsh ufo.geo -1
> Gmsh 1.52.1, started Sat May 29 16:54:37 2004
> Command line : gmsh ufo.geo -1
> Info : Parsing file 'ufo.geo'
> Info : Parsed file 'ufo.geo'
> Mesh 1D...
> Meshing Curve 1
> Meshing Curve 2
> Meshing Curve 3
> Mesh 1D complete (-8.3348e-19 s)
> Info : Writing mesh file 'ufo.msh'
> Info : Saving all elements (discarding physical groups)
> Info : 50 nodes
> Info : 50 elements
> Info : Wrote mesh file 'ufo.msh'
> 
> But, the 2D meshing command given an error and proceeds to
> create weird geometry:
> 
> [doofus:gmsh]>gmsh ufo.geo -2
> Gmsh 1.52.1, started Sat May 29 14:42:14 2004
> Command line : gmsh ufo.geo -2
> Info : Parsing file 'ufo.geo'
> Info : Parsed file 'ufo.geo'
> Mesh 1D...
> Meshing Curve 1
> Meshing Curve 2
> Meshing Curve 3
> Mesh 1D complete (-4.1674e-19 s)
> Mesh 2D...
> Meshing Surface 4
> Error : Ellipse -2 is wrong
> Error : Ellipse -1 is wrong
> Error : Ellipse 1 is wrong
> Error : Circle or ellipse arc 1 greater than/equal to Pi (angle=6.28319)
>       : (If you understand what this implies, you can disable this error
>       : message by setting Geometry.CircleWarning to 0. Otherwise, please
>       : subdivide the arc in smaller pieces)
> Error : Ellipse 2 is wrong
> Error : Circle or ellipse arc 2 greater than/equal to Pi (angle=6.28319)
>       : (If you understand what this implies, you can disable this error
>       : message by setting Geometry.CircleWarning to 0. Otherwise, please
>       : subdivide the arc in smaller pieces)
> Info : Relaxation factor = 0.75
> Info : Relaxation factor = 0.5625
> Info : Relaxation factor = 0.421875
> Info : Relaxation factor = 0.316406
> Info : Relaxation factor = 0.237305
> Info : Relaxation factor = 0.177979
> Info : Relaxation factor = 0.133484
> Info : Relaxation factor = 0.100113
> [it continues this forever, restarting at 0.75 every 20-30
> cycles]
> 
> I can open the .geo file in the GUI and everything looks
> fine. When I mesh in the GUI, the same thing happens.
> Has anyone seen this before? Is there a problem in the RPM
> or my input file?
> 
> I ultimately wish to create a triangulated surface mesh for a
> 10:10:1 ellipse. This is merely 1/6th of the final surface.
> 
> Mark
> _______________________________________________
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> gmsh at geuz.org
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> 
> 


-- 
Christophe Geuzaine
Applied and Computational Mathematics, Caltech
geuzaine at acm.caltech.edu - http://geuz.org