Interactive selection of cells based on ParaView generated parameters

praneeth · October 18, 2023, 1:02pm

Hi all,

I am still new to ParaView and this issue I have did not appear in previous threads so I thought to raise a new one.

A few days ago I asked a question about using ParaView GUI to identify faces of a given geometry and got suggested this beautiful solution by @Kenneth_Moreland: Accessing points associated to a cell from the Programmable Filter or Python Shell - #5 by Kenneth_Moreland

Based on the method of @Kenneth_Moreland, I was able to access individual faces by a property RegionId, which is created from the Connectivity filter.

I am now trying to select the individual faces based on this RegionId. I can already do this using the Find Data panel, as shown in the image below:

Using the Extract option in Find Data gives me the selected surface (All cells with RegionId=7).

Is it also possible to do the same selection of the surface (i.e., all cells with RegionId=7) via GUI? Perhaps there is an option within selecting within Views that is not obvious to a newbie like me? (Relevant docs page: 6. Selecting Data — ParaView Documentation 5.11.0 documentation).

A relevant ParaView state file for the star geometry in the image above is attached to this post.

Many thanks in advance for your help and advice!
Praneeth

Attachment:
star.pvsm (532.3 KB)

Kenneth_Moreland · October 18, 2023, 2:07pm

You cannot do it directly. But what you can do is convert the single mesh with RegionID into a partitioned structure that the ParaView GUI will understand.

There is no direct filter to do it, but it has been discussed before: How to create a collection of blocks (multi block) based on connectivity. The instructions there are a bit out of date, so here is an update.

Create a Programmable Filter. Set the output data type to vtkPartitionedDataSet. Set the script to the following:

import vtk
inp = self.GetInputDataObject(0, 0)
out = self.GetOutput()

outData = vtk.vtkPartitionedDataSet()

rangeID = inputs[0].CellData.GetArray('RegionId').GetRange()
outData.SetNumberOfPartitions(int(rangeID[1]) + 1)

for ic in range(int(rangeID[0]), int(rangeID[1]) + 1):
    thresh = vtk.vtkThreshold()
    thresh.SetInputData(inp)
    thresh.SetInputArrayToProcess(0,0,0,
        vtk.vtkDataObject.FIELD_ASSOCIATION_CELLS,'RegionId')
    
    thresh.SetLowerThreshold(ic-0.5)
    thresh.SetUpperThreshold(ic+0.5)
    thresh.Update()
    tooutData = thresh.GetOutputDataObject(0)
    outData.SetPartition(ic, tooutData)

out.DeepCopy(outData)

This will run internally run the threshold filter on all region ids and then collect them into a vtkPartitionedDataSet.

Once you have a vtkPartitionedDataSet, you can use select block (or just hit b) in the view and click on a face to select it.

star-blocks.pvsm (670.2 KB)

praneeth · October 24, 2023, 9:52am

Hi @Kenneth_Moreland, I had the chance to try this solution out today, and it works really well!

I initially had some issues, I could not get a python package pygments to work on the Programmable Filter; and our ParaView installation is made through Spack (which has a separate python installation for ParaView) so it would not have been straightforward to fix. But when I reset the ParaView and tried running the Programmable Filter, I no longer had the issue.

For other readers of this thread, I also get this error when running the Programmable Filter:

( 174.785s) [paraview ]vtkDemandDrivenPipeline:776 ERR| vtkCompositeDataPipeline (0xce96a00): Input for connection index 0 on input port index 0 for algorithm vtkExtractBlockUsingDataAssembly (0x130e4180) is of type vtkPartitionedDataSet, but a vtkPartitionedDataSetCollection is required.
( 174.786s) [paraview ]vtkDataAssemblyUtilitie:815 ERR| GetSelectorForCompositeId is only supported on a data-assembly representation a hierarchy.
( 174.787s) [paraview ]vtkDataAssemblyUtilitie:815 ERR| GetSelectorForCompositeId is only supported on a data-assembly representation a hierarchy.
( 194.500s) [paraview ]vtkDataAssemblyUtilitie:815 ERR| GetSelectorForCompositeId is only supported on a data-assembly representation a hierarchy.

But this error had no effect on the selection of the “blocks”. After the programmable filter. I was able to use and Extract Selection to get the faces that I wanted.

Thanks again for the quick and effective advice!

Praneeth

mwestphal · October 24, 2023, 11:26am

Alternatively you can use the selection by point/cell data directly:

Open your dataset
Connectivity, Apply
ColorBy regionId, cell or point
Select by cell/point data: