[dune-pdelab] Writing subtree of a CompositeGridFunctionSpace to VTK

[Oliver Sander]

Am 23.06.2015 um 12:27 schrieb Christian Engwer:
> Hi Oli,
> 
>> There is one problem, though: The first subtree my space is a displacement field.
>> When using my original code, that subtree appeared in ParaView as one data set 'displacement',
>> and I could use the warp-by-vector filter, for example.
> 
> this was a special trick that PDELab could use, as the GFS contains
> the VectorGridFunctionSpace in the tree.
> 
>> When using the code snippet you
>> propose, the three components of the displacement appear as separate scalar fields 'displacement0',
>> 'displacement1', 'displacement2'.  How can I keep them as a single data set?
> 
> As the SubTree is now an object on its own and doesn't exhibit the
> VectorGridFunctionSpace tag anymore the transformation doesn't detect
> the vector type of your GFS anymore.

Hmm, why should that tag disappear?  On first sight this sounds like a bug to me,
but I'm sure in a second you will tell me that there is a good reason for it :-)


> You would have to abjust the
> transformations employed when constructing the SubGFS. I'm not sure
> how difficult it is. As a work-around you can merge them again in
> paraview, using the calculator:
> 
> Result = iHat * displacement0 + jHat * displacement1 + kHat * displacement2

I'd dislike doing this, but it seems like I have to:  in 3d my overall space has
8 components, and the VTKWriter flat-out refuses to write that.

Cheers,
Oliver

> 
> 
> Christian
> 


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