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<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">I'm afraid there is no guarantee. This has nothing directly to do with dgf but with the general<br>
structure of the dune grid interface. A grid manager could require a specific orientation - so I think<br>
alu originally required triangles to be oriented counter clock wise (but alu was originally only for<br>
the flat case); another grid manager could require clock wise <br>
The documentation for dgf is merely stating that you do not need to know what the grid manager requires
<br>
but can use any orientation. <br>
That also means that the question if orientation is preserved must depend on the grid manager used.<br>
Afaik alugrid and alberta will preserve the orientation you use in the dgf file - as grids supporting surface<br>
clockwise or counter clockwise does not really make a lot of sense any more...<br>
Andreas<br>
<br>
<br>
<br>
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<div style="direction: ltr;" id="divRpF145197"><font color="#000000" face="Tahoma" size="2"><b>From:</b> dune-bounces+a.s.dedner=warwick.ac.uk@dune-project.org [dune-bounces+a.s.dedner=warwick.ac.uk@dune-project.org] on behalf of Sacconi, Andrea [a.sacconi11@imperial.ac.uk]<br>
<b>Sent:</b> 27 September 2012 17:10<br>
<b>To:</b> dune@dune-project.org<br>
<b>Subject:</b> [Dune] DGF format and local ordering of vertices<br>
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<div style="direction:ltr; font-family:Tahoma; color:#000000; font-size:10pt">Hi everyone,<br>
<br>
I'd like to ask you a question about the Dune Grid Format (DGF) and the ordering of the corners in an element of the mesh.<br>
<br>
Suppose I put my vertices and my simplices in a dgf file, and then I use it to feed the grid constructor (Alberta, ALUGRID, whatever).<br>
In the online documentation about the DGF, under the field "Simplex", I read that "no ordering of local vertices is required".<br>
In my particular case, however, I do need a special ordering, since I'm dealing with hypersurfaces. To set an example: if you have the unit cube as initial geometry, I need that, looking from outside, all the triangles have corners counter-clockwise oriented
s.t. the unit normal points outward. I do need that this ordering (used in .dgf file) is preserved!<br>
<br>
Is there any way of knowing whether this important information is preserved? Otherwise, the computation of the normal to each triangle could lead to weird results (strong nonsymmetric time-dependent behaviour for initial symmetric configurations).<br>
<br>
Thanks for your help!<br>
<br>
Andrea<br>
<div>__________________________________________________________<br>
<div style="font-family:Tahoma; font-size:13px"><br>
Andrea Sacconi<br>
PhD student, Applied Mathematics<br>
AMMP Section, Department of Mathematics, Imperial College London,<br>
London SW7 2AZ, UK<br>
a.sacconi11@imperial.ac.uk<br>
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