[Gmsh] problem meshing extruded ellipse

Mark Stock mstock at umich.edu
Sat May 29 23:14:33 CEST 2004


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:

[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