[Paraview] Seeking advice for high-order and high-dimensional discontinuous Galerkin data

[Felipe Bordeu]

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In our lab we work with data defined in 1D,2D, to 18D or more dimension.
We have our own format file (Separated Representatioin/ Tensorial
product) to store everything, and we use a custom plugin to load
(generate) only a slice (a 3D slice) of the High dimensional data.

this is a video of our plugin (with a 6D solution)

 http://www.youtube.com/watch?v=o6Vzww_cmhA

Hope will be inspiring.
Felipe




Le 11/04/2014 08:40, Noah Reddell a écrit :
>  I am trying to setup a visualization solution for my research code
> which produces structured, nodal data, based on a discontinuous Galerkin
> solution method for fluid equations.
> 
> 
>   * The domain is either 2D, 3D, 4D, 5D, or 6D.  Yes, greater than 3D,
>     because my primary model produces kinetic data sampled in phase
>     space (3D position and 3D velocity).
>   * The domain is discretized by elements that are generalized
>     N-dimensional quadrilaterals. (quadrilaterals, hexahedrals, etc.)
>     organized in a block-structured mesh.
>   * The solution on any given element is smooth, represented by
>     arbitrary order polynomials and sampled at surface and interior node
>     locations.  I tend to use high order elements compared to typical
>     practice, i.e. 7th, 8th, 9th-order. I’d like the visualization to
>     capture some of the element’s internal solution structure rather
>     than just a linear interpolation between element vertices.
>   * The solution is multi-valued at faces where two elements are
>     adjacent and I want the visualization to well-capture the surface
>     discontinuity.
>   * My mesh and nodal data are both stored in HDF5 files, with some
>     flexibility to modify formatting.
> 
> 
> 
> I spent some time reviewing the ParaView user guide and document for
> plugin reader development and now have a few questions before I can proceed.
> 
> Obviously ParaView is focused on 2D and 3D data. The underlying VTK
> looks to only handle up to 3D vertex position vectors, for example.  My
> takeaway from this, is it is not possible to describe a 4D or higher
> mesh to ParaView directly.  That’s not surprising but seems to suggest I
> will have to write a custom reader plugin to access my 4D+data.  My
> survey of the documentation makes me think that I’ll be able to provide
> parameters to the reader plugin that control the dataset.  For example,
> specify what dimensions to slice and where to slice.  I suppose I need
> to similarly parameterize the load of the mesh.  Does this sound like a
> workable approach?
> 
> For the data discontinuities at element faces, I’ve seen discussions in
> this forum that suggest unstructured grids with duplicated/co-located
> vertices allows for assigning two different data values at the same
> physical location.  Since I am working with structured grids and data,
> I’m wondering if a different technique might work.  How about inserting
> zero-volume collapsed elements between each real element?  In this way,
> the real elements are still adjacent, but their vertices / nodes can be
> assigned different vales.  One concern I have is the hidden element
> would have zero-volume.  I’d hate to develop that design and then have
> some ParaView internal function break due to a divide by zero error or
> something similar.  Another problem area might be plotting stream tubes
> from the data set.
> 
> Lastly, for the high order visualization, I thinking the most straight
> forward approach is to interpolate my structured high order elements
>  into a new fine mesh of structured linear elements.  That should be
> good enough.  On this forum, vtkBridgeDataSet has been mentioned as a
> possible approach but requiring much development effort.  That was
> several years ago.  Has there been any progress by others with similar
> high-order or spectral data sets?
> 
> Here’s an old thread that brought up the same basic goals as
> mine: http://www.paraview.org/pipermail/paraview/2006-October/003899.html
> (The numerical scheme and element types are not exactly what I’m working
> on, but the ideas are similar.)
> 
> I really appreciate any feedback.
> 
> Best Regards,
> 
> Noah Reddell
> University of Washington
> 
> 
> 
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- -- 
Felipe Bordeu Weldt
Ingénieur de Recherche
- -------------------------------------
Tél. : 33 (0)2 40 37 16 57
Fax. : 33 (0)2 40 74 74 06
Felipe.Bordeu at ec-nantes.fr
Institut GeM - UMR CNRS 6183
École Centrale Nantes
1 Rue de La Noë, 44321 Nantes, FRANCE
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