[Gmsh] Where's Node 1

[Christophe Geuzaine]

Joe Koski wrote:

> When I enter the following geometry description on GMSH 1.52.1 under Mac OS
> X 10.3.4
> 
> lc = 0.015;
> Point(1) = {0,0,0,lc};
> Point(2) = {1,0,0,lc};
> Point(3) = {0,1,0,lc};
> Point(4) = {-1,0,0,lc};
> Point(5) = {0,-1,0,lc};
> Point(6) = {0.9492,0,0,lc};
> Point(7) = {0,0.9492,0,lc};
> Point(8) = {-0.9492,0,0,lc};
> Point(9) = {0,-0.9492,0,lc};
> Circle(1) = {2,1,3};
> Circle(2) = {3,1,4};
> Circle(3) = {4,1,5};
> Circle(4) = {5,1,2};
> Circle(5) = {6,1,7};
> Circle(6) = {7,1,8};
> Circle(7) = {8,1,9};
> Circle(8) = {9,1,6};
> Line Loop(9) = {2,3,4,1};
> Line Loop(10) = {5,6,7,8};
> Plane Surface(11) = {9,10};
> Physical Line(12) = {1};
> Physical Line(13) = {4};
> Physical Surface(14) = {11};
> Recombine Surface {11} = 85;
> 
> And then do a 2d mesh of the geometry, I get a successful mesh, but there is
> no Node 1 in the .msh file. The node numbering scheme starts with 2. Is this
> something that I'm doing? The start of the .msh file looks like this
> 
> $MeshFormat
> 2 0 8
> $EndMeshFormat
> $Nodes
> 1849
> 2 1 0 0
> 3 0 1 0
> 4 -1 0 0
> 5 0 -1 0
> 6 0.9492 0 0
> 7 0 0.9492 0
> 8 -0.9492 0 0
> 9 0 -0.9492 0
> 10 0.9998859396174979 0.01510323658138523 0
> 11 0.9995437844895334 0.03020302780088747 0
> ...
> 

And there's nothing wrong with that ;-)

Check the documentation: the node/element lists in the .msh format are
*not* supposed to be dense. (Besides, we keep the geometrical point
numbers intact the mesh file, and point 1 clearly does not belong to the
mesh).

Best,

Christophe

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