Hi
Sorry for the delay, I was a little bussy with some homework.
Apparently deal.ii needs the cell vertices given in anticlockwise
sense. The points define the vertices but the lines and line loops
define the sense. So, for example consider the next cell:
p1 ----------- p2
| |
| |
| |
| |
p4 ------------ p3
I could define the lines as (in gmsh format):
l01 = newl; Line(l01) = {p01,p02}
l02 = newl; Line(l01) = {p02,p03}
l03 = newl; Line(l01) = {p03,p04}
l04 = newl; Line(l01) = {p04,p01}
So, the lines sense would be:
p1 ----------> p2
^ |
| |
| |
| v
p4 <----------- p3
If I a line loop with this lines:
ll01 = newll; Line Loop(ll01) = {l01,l02,l03,l04}
and then I define a surface I would receive the error message when I try
to import the cell into deal.ii.
To correct the error I can redefine the lines:
l01 = newl; Line(l01) = {p04,p03}
l02 = newl; Line(l01) = {p03,p02}
l03 = newl; Line(l01) = {p02,p01}
l04 = newl; Line(l01) = {p01,p04}
or redefine the line loop:
ll01 = newll; Line Loop(ll01) = {-l01,-l02,-l03,-l04}
In this way I obtain a cell in anticlockwise sense:
p1 <---------- p2
| ^
| |
| |
v |
p4 -----------> p3
And then deal.ii accept the cell.
The problem was that I defined randomly the sense of lines and line
loops because I wasn't aware of this requirement. So, after a couple of
hours fixing the lines deal.ii accepted my mesh.
Of course you need to do this with all the line loops and surfaces in
your grid.
I hope you find this helpful.
Best regards
Javier Muñoz
El lun, 26-09-2011 a las 15:04 +0100, Ted Kord escribió:
> Hi,
>
>
> Could you possibly let me know how you re-ordered the vertices in the
> gmsh file?
>
>
> Regards,
>
>
> Ted
>
>
> On 25 September 2011 23:55, Javier Muñoz <[email protected]>
> wrote:
> Thank you for your answer. You are right, it was an error in
> the
> vertices order. I reorder them again and I was able to import
> the mesh
> into deal.ii.
>
> Regards
> Javier Muñoz
>
>
>
> El dom, 25-09-2011 a las 16:10 -0500, Wolfgang Bangerth
> escribió:
>
> > > Then, when I tried to import the mesh into deal.ii and it
> gave the
> > > error:
> > >
> > > terminate called after throwing an instance of
> > > 'dealii::StandardExceptions::ExcInternalError'
> > > what():
> --------------------------------------------------------
> > > An error occurred in line <642> of file
> > > </home/zerpiko/FEM/deal.II/source/grid/grid_reordering.cc>
> in function
> > > static void dealii::GridReordering<dim,
> > > spacedim>::invert_all_cells_of_negative_grid(const
> > > std::vector<dealii::Point<spacedim> >&,
> > > std::vector<dealii::CellData<dim> >&) [with int dim = 2,
> int spacedim =
> > > 2]
> > > The violated condition was:
> > > n_negative_cells==0 || n_negative_cells==cells.size()
> > > The name and call sequence of the exception was:
> > > ExcInternalError()
> > > Additional Information:
> > > (none)
> > > --------------------------------------------------------
> > >
> > > I think is something related with reordering cells. There
> are any other
> > > restrictions that a mesh must fulfill? Tnks.
> >
> > It's hard to tell without a concrete input file. I believe
> what the error
> > message is trying to tell you is that the code found that
> some of your cells
> > have negative volume since the vertices are specified in the
> wrong order or
> > the cell is degenerate, but that not *all* cells have
> negative volume (in
> > which case one could simply flip all cells).
> >
> > You'll have to take a look at the input file to find out
> whether it's an error
> > in the code or whether it's a problem in the input mesh.
> >
> > Best
> > W.
> >
> >
>
> -------------------------------------------------------------------------
> > Wolfgang Bangerth email:
> [email protected]
> > www:
> http://www.math.tamu.edu/~bangerth/
>
>
> _______________________________________________
> dealii mailing list
> http://poisson.dealii.org/mailman/listinfo/dealii
>
>
>
>
>
> --
> Best regards,
>
>
> Theodore
>
>
>
>
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