[Gmsh] normals (again)

[Christophe Geuzaine]

John Borchardt wrote:
> Hi, please see attached screenshot.  The geometry normal is in red and
> the mesh normals are in green -- and they are pointing in opposite
> directions as far as I can tell.
> 
> The .geo file that produced this is:
> 
> Point(1) = {0,0,0,0.1};
> Point(2) = {1,0,0,0.1};
> Point(3) = {0,1,0,0.1};
> Line(1) = {1,2};
> Line(2) = {2,3};
> Line(3) = {3,1};
> Line Loop(4) = {1,2,3};
> Plane Surface(5) = {4};
> 
> The console output is:
> 
> Info    : -------------------------------------------------------
> Info    : Gmsh version   : 2.0.8
> Info    : Build OS       : Linux
> Info    : Build options  : GSL NETGEN JPEG PNG ZLIB MATHEVAL ANN
> Info    : Build date     : Sat Aug 11 17:09:17 GMT 2007
> Info    : Build host     : yellow
> Info    : Packager       : buildd
> Info    : Home directory : /home/john/
> Info    : Launch date    : Fri Feb 15 11:54:09 2008
> Info    : Command line   : gmsh plate.geo
> Info    : -------------------------------------------------------
> Info    : Reading 'plate.geo'
> Info    : Read 'plate.geo'
> Info    : Meshing 1D...
> Info    : Meshing curve 1
> Info    : Meshing curve 2
> Info    : Meshing curve 3
> Info    : Mesh 1D complete (0 s)
> Info    : Mesh
> Info    : Meshing 2D...
> Info    : Meshing surface 5 (Plane, MeshAdapt+Delaunay)
> Info    : Mesh 2D complete (0.004 s)
> Info    : Mesh
> Info    : 21 vertices 40 elements
> Info    : Meshing 3D...
> Info    : Mesh 3D complete (0 s)
> Info    : Mesh
> Info    : 21 vertices 40 elements
> Info    : Reading 'plate.geo'
> Info    : Read 'plate.geo'
> Info    : Meshing 1D...
> Info    : Meshing curve 1
> Info    : Meshing curve 2
> Info    : Meshing curve 3
> Info    : Mesh 1D complete (0.004001 s)
> Info    : Mesh
> Info    : Meshing 2D...
> Info    : Meshing surface 5 (Plane, MeshAdapt+Delaunay)
> Info    : Mesh 2D complete (0 s)
> Info    : Mesh
> Info    : 22 vertices 42 elements
> 
> 
> Any ideas what's going wrong?  I am using Ubuntu 7.10 x86-64 and I


You wouldn't have the "Reverse all normals" option checked in 
Tools->Options->Mesh->Light, by any chance?







> installed via apt-get I believe.  Thanks!
> 
> 
> --John
> 
> 
> 
> 
> 
> 
> On Fri, Feb 15, 2008 at 11:32 AM, Christophe Geuzaine
> <cgeuzaine at ulg.ac.be> wrote:
>> John Borchardt wrote:
>>  > Sorry I am looking in the manual and list archives and I still don't
>>  > understand...
>>  >
>>  > Can you tell me if the default behaviour of gmsh is such that mesh
>>  > element normals are opposite of the surface normals?  Am using version
>>  > 2.0.8.
>>  >
>>  > E.g., when I mesh the following .geo, the element normals are opposite
>>  > of the surface normal...
>>
>>
>>  I cannot reproduce this on my machine...
>>
>>
>>
>>  >
>>  >
>>  > Point(1) = {0,0,0,0.1};
>>  > Point(2) = {1,0,0,0.1};
>>  > Point(3) = {0,1,0,0.1};
>>  > Line(1) = {1,2};
>>  > Line(2) = {2,3};
>>  > Line(3) = {3,1};
>>  > Line Loop(4) = {1,2,3};
>>  > Plane Surface(5) = {4};
>>  >
>>  >
>>  >
>>  > Thanks,
>>  >
>>  >
>>  > --John
>>  >
>>  > _______________________________________________
>>  > gmsh mailing list
>>  > gmsh at geuz.org
>>  > http://www.geuz.org/mailman/listinfo/gmsh
>>  >
>>  >
>>
>>
>>  --
>>  Prof. Christophe Geuzaine
>>  University of Liege, Electrical Engineering and Computer Science
>>  http://www.montefiore.ulg.ac.be/~geuzaine
>>
>>
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>>
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine