[dune-pdelab] Visualization of Gauss point data

[Christian Engwer]

Hi Christian,

I know that Markus asked you to write to the pdelab list, but actually
this a problem of VTK. VTK can only handle point and cell
data. Visualization at quadraturepoints is not possible using VTK and
thus not possible using vtkwriter. What you can do is, use your data
and visualize "just" as pointdata ist using vtkwriter. This will give
you the values in cell vertices. If you have discontinuous data you
can pass the corresponding parameter to the vtkwriter. If you have
higher order data you can use the subsampling vtk writer.

How do you represent your stresses? Why do you compute these at the
gauss points? I suggest you first decide on the functions space for
your stresses and the use the appropriate discrete grid function. You
can now write an adapter which computes the stresses in a given point
and map the results to the discrete grid function using "interpolate".

Christian

On Wed, Jul 20, 2011 at 02:45:10PM +0200, Christian Simon wrote:
>    Dear all,
> 
>    I moved this question from the dune mailing list to the dune-pdelab
>    mailing list.
> 
>    Here is the problem:
>    I computed stresses at the Gauss points resulting from the deformation
>    gradients in my local operator. Now I wonder, how I can visualize these
>    stresses via vtkwriter directly from the local operator, which is on
>    element basis, without a second calculation of the variable in the driver
>    *_Q2.hh or somewhere else? Or is there a way to assign these stress values
>    to a vector container and visualize it in the driver *_Q2.hh?
> 
>    Maybe it is possible to extrapolate these values to the nodes within the
>    operator and assign the values to a vector container, which in turn can be
>    visualized by the vtkwriter?
> 
>    Is this there a solution for this problem?
> 
>    Thank you in advance,
>    Christian Simon

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