Merging simulation data from vtk and vtu files

I would like to merge two simulation data sets, one based on a structured and one on an unstructured mesh together and validate my model against another one by computing absolute value differences of certain quantities.

I saw that some people ran into the same issues after grouping, getting an appendix (Partial) to all their scalar fields and not being able to compute a new scalar field computed from both, quantities of dataset 1 and 2. They were advised to try the AppendAttributes filter.

I did all that. Still, after applying the AppendAttributes filter, the quantities are still (partial). And I can plot quantities of either dataset 1 or 2, but as soon as I use the calculator to computer something like abs(q1-q2) I always get “Syntax error: Operator expected;” and the calculator result gets appended by (?).

If I understand it correctly, I do not have to interpolate both datasets onto a single mesh as this is done implicitly. Am I wrong about that? Or is it maybe not possible to combine data from structured/unstructured meshes?

Thanks a lot for your help!

AppendAttributes would only make sense if both your inputs have the same number of cells and points.

If that is not the case, you want to use ResampleWithDataset.

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Thank you for that information.

When I apply the filter ResampleWithDatasets, I am asked to specify either a source or an input - but only one, I cannot select both sources/inputs. I tried applying the filter on the already grouped together datasets and also tried to apply it on dataset 1 and specify dataset 2 as a source/input in the filter. But both approaches don’t work. I get an error ‘Algorithm vtkPResampleWithDataSet(0x14feb7ba0) returned failure for request’.


  • Click on the dataset containing data arrays you want to resample
  • Add a ResampleWithDataSet filter
  • In the input window, click on the “Destination Mesh” radio box
  • In the input window, click on the dataset you want to use the geometry as output
  • Click on OK
  • Check PassPointData and PassCellData arrays,
  • Apply
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Thank you so much for your reply!

I just realized, on our cluster an older Paraview 5.6 version is installed, why I couldn’t find the “Destination Mesh” radio box nor the PassPointData and PassCellData options. Repeating your steps with “Source” instead of “Destination Mesh” in Paraview 5.6 still results in an error once I use the calculator after sampling and subsequent grouping: “Syntax error: expecting a variable name.”

So I will try this again with Paraview 5.8. Thanks again.

Indeed, the naming were changed a few months ago to avoid confusion. Let me know.