[Paraview] Field Divergence: vtkImageDivergence and XML

[Simone Crippa]

Hi,

some time ago I tried vtkImageDivergence to compute the vorticity out of a
velocity field. This was before the wiki-page on vtkCellDerivatives was
written.

I am not sure what is wrong with vtkImageDivergence in your case, but I
think you should be able to construct your required field out of the 9
velocity derivatives (du/dx, du/dy, ...) that you get out of the
vtkCellDerivatives filter.

Maybe I am missing something of your requirements, or maybe you didn't
notice the drop-down selection of the vtkCellDerivatives filter. (in your
case the "ComputeGradient" option).


Regards, Simone


> I'm looking for a way to color isosurfaces by the divergence of a
> velocity vector field. It looks like the vtkImageDivergence class is
> the one I need.[1] Please correct me if I'm wrong about that.
>
> To add the vtkImageDivergence class to the ParaView GUI, I tried to
> modify the XML files from the vtkCellDerivatives example in the Wiki.
> [2] My XML files (GUI and SM) are below. They do give me a
> "Divergence" entry in my Filters menu, and the filter will allow me
> to choose an input and Accept. But there is no apparent output from
> the filter. Is this just a syntax error in my XML, or is there
> another problem?
>
> Thanks,
> ccg
>
> [1] http://www.vtk.org/doc/release/5.0/html/a01515.html
> [2] http://www.paraview.org/Wiki/ParaView:Extend
>
> ---- vtkImageDivergence.xml ----
>
> <ModuleInterfaces>
>    <ServerManagerFile name="vtkImageDivergence.pvsm" />
>
>    <Module name="ImageDivergence"
>            menu_name="Divergence"
>            root_name="Divergence"
>            module_type="Filter"
>            long_help="Compute divergence of a field."
>            short_help="Compute divergence of a field.">
>      <Filter class="vtkImageDivergence">
>        <Input name="Input"
>               class="vtkDataObject"/>
>      </Filter>
>      <InputMenu trace_name="Input" label="Input" property="Input"
>                 help="Set the input to this filter."
>                 input_name="Input"/>
>      <Documentation>
> Compute the divergence of a field.
>      </Documentation>
>    </Module>
> </ModuleInterfaces>
>
> ---- vtkImageDivergence.pvsm ----
>
> <?xml version="1.0"?>
> <ServerManagerConfiguration>
>    <ProxyGroup name="filters">
>     <SourceProxy name="ImageDivergence" class="vtkImageDivergence">
>       <InputProperty
>          name="Input"
>          command="SetInput">
>            <ProxyGroupDomain name="groups">
>              <Group name="sources"/>
>              <Group name="filters"/>
>            </ProxyGroupDomain>
>            <DataTypeDomain name="input_type">
>              <DataType value="vtkDataObject"/>
>            </DataTypeDomain>
>       </InputProperty>
>     <!-- End ImageDivergence -->
>     </SourceProxy>
>    </ProxyGroup>
> </ServerManagerConfiguration>
>
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-- 
Simone Crippa
Research assistant, Dipl.-Ing.
Royal Institute of Technology (KTH)
Aeronautical and Vehicle Engineering
Division of Aerodynamics
Teknikringen 8
SE-10044 Stockholm, Sweden
+46 (0)8 790 6465