[aspect-devel] Duplicate Vertices

[Wolfgang Bangerth]

> The easiest thing I can think of is to post process the files to be
> more suitable for visualization.  Another option is to have a flag in
> the output file classes to disallow discontinuous values, or write
> only one of the stored values at a vertex.  Any thoughts?

My reluctance to address this is not based on perceived lack of need but 
instead on knowing what it would entail. Let me explain how this is 
currently implemented:
   when you call DataOut::build_patches, the data in the finite element
      fields is transformed into an internal representation; this
      internal representation is cell-based, i.e., it already has the
      duplicate vertices and represents all fields as discontinuous
      (even if one of the fields that are to be output is, in fact,
      continuous).
   when you call something like DataOutBase::write_vtk, all it does is
      take this intermediate representation and output it in one
      particular format; there are other producers of this intermediate
      format in deal.II apart from DataOut -- e.g., MatrixOut. But the
      beauty of an intermediate format is that you can separate the
      N different ways to generate intermediate format from the output
      in M different file formats -- the effort becomes N+M, not N*M.

What I mean to say by this is that changing the ways this currently 
works is not an easy task. Presumably, if one wanted to address this 
issue, the way to go would be to work in the output writer (e.g., 
DataOutBase::write_vtu) to reconstruct some of the information such as 
which vertex is where and which other vertices it equals. It is 
certainly also possible to augment the intermediate format by 
information that output writers may or may not use. But in any case, 
it's not going to be a quick exercise :-(

Best
  W.


-- 
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Wolfgang Bangerth               email:            bangerth at math.tamu.edu
                                 www: http://www.math.tamu.edu/~bangerth/