[aspect-devel] [deal.II] Duplicate Vertices

[Eric Heien]

Hi all,

It's been a while since this thread was active, so I'll put up a quick refresher.  Originally I noticed the deal.ii output has redundant vertices which causes large files and potential trouble with visualization algorithms (this is covered in the deal.ii FAQ).  I asked about changing the code to support a slimmer format and several people discussed how it was difficult given the current structure of deal.ii.

I won't have time to implement this for a while, but here's what I'm thinking of doing:

- Create a class named "DataOutFilter" to hold vertices, cells, and data values associated with an output file.  This will have flags regarding whether to remove or average duplicate values on the same vertex, merge vertices within certain distances, etc.

- Other output classes (VtkStream, HDF5MemStream, etc) can be rewritten to utilize this for internal storage, but for now I'll just alter HDF5MemStream since that's what I'm using for large data sets.  I imagine some output formats aren't commonly used for large results (e.g. gnuplot) so there's little reason to change them.

In this way, deal.ii can still allow many different output formats and each format shouldn't require too much modification to handle duplicate vertices.  I realize the idea of storing and processing values before output isn't in line with the "*Stream" name given to output classes.  Is there a particular reason why these are named streams, or is it just a convention to go along with the C concept of streams?

Does anyone see any problems with this approach, or suggestions for how to improve it?

Thanks,

-Eric

On Dec 14, 2012, at 12:24 AM, Guido Kanschat wrote:

> Dear Eric,
> 
> it might be worth looking at the output functions for OpenDX (write_dx()). There, at least connectivity between patches is recovered, such that streamlines could be computed on non-adaptive meshes.
> 
> Unfortunately, nobody cared for OpenDX anymore, and it was never extended to adaptive meshes.
> 
> As for discontinuous functions: averaging.
> 
> Best,
> Guido
> 
> 
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