[Dune] Element transformation/renumbering in GridFactory

[Simon Praetorius]

Hi Christian,

Does this include the local numbering of ther vertices in an element? Yes, I can get the insertion index of an element or a vertex index, but how to extract from this the changed local numbering of an element. (Do I mix something up here?)


Example: AlbertaGrid has to make sure that the numbering of the element vertices is such that the refinement-edge is numbered first. If this is not given by the mesh-file, the local numbering is updated in all elements until this property is fulfilled globally (works only in 2d, ALUGrid implements a different strategy also with renumbering the elements). So, the vertex and element indices are not relevant here (might be the same as the insertion-index). Just how these indices are ordered in the element locally matters for me. It might be that the orientation of an element is flipped or the element is just "rotated" in the sense that the first corner is changed to another corner and thus the local coordinate-system of the element is changed.


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Dr. Simon Praetorius
Institut für Wissenschaftliches Rechnen
Fakultät Mathematik
Technische Universität Dresden
Tel.: TUD-34432
Mail: simon.praetorius at tu-dresden.de<mailto:simon.praetorius at tu-dresden.de>
Web: www.math.tu-dresden.de/~spraetor<http://www.math.tu-dresden.de/~spraetor>
________________________________
Von: Christian Engwer <christian.engwer at uni-muenster.de>
Gesendet: Montag, 13. April 2020 10:57
An: dune at lists.dune-project.org; Praetorius, Simon; dune at lists.dune-project.org
Betreff: Re: [Dune] Element transformation/renumbering in GridFactory

Dear Simon, this information is available via the grid factory using the insertion index methods. These allow to map cells and vertices to their respective index on the mesh file.

Best
Christian

Am 13. April 2020 01:10:20 MESZ schrieb Simon Praetorius <simon.praetorius at tu-dresden.de>:

Hi Dune community,

I have a question regarding the elements constructed by a grid factory. When inserting elements, it seems not required that the order of the vertices is preserved by the grid, i.e. inserting an element with vertices 0,1,2 might result in an element that has corners 2,0,1. An example is the ALUGrid GridFactory. How can I get this reordering (from a grid-factory), without comparing coordinates? Or better: how can I get the local geometry transformation to get the coordinates transformed from the real grid element coordinates, to coordinates in the original element inserted into the grid-factory?

I need this to construct an element-parametrization in a grid reader. The information the reader has is just its own vertex numbering and from this a parametrization can be constructed. But if the vertex numbering changes, also the local coordinates change and thus this parametrization can not be used anymore.

Best regards,
Simon
________________________________
Dr. Simon Praetorius
Institut für Wissenschaftliches Rechnen
Fakultät Mathematik
Technische Universität Dresden
Tel.: TUD-34432
Mail: simon.praetorius at tu-dresden.de
Web: www.math.tu-dresden.de/~spraetor
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