Clip from polygonal mesh?

[caladoa (Andre Calado)]

Greetings,

I have a bit of a tricky problem to tackle with Paraview in terms of filtering / clipping.

I have a cell var (phi) which for phi=0 defines an an interface (surface). I would like to isolate each of these separately as if they were “bubbles” (see image below). Basically there is a large surface, and a bunch of smaller bubbles above (actually droplets) and below the large surface. If I use the connectivity filter, I am able to split these into separate surface meshes, which is what I want. Plus, if I order the regions by ascending cell count, the last region ID (largest) will give me the large surface (from which I can do other operations).
However, now I want to isolate exclusively the ones which lie below (lower Z value) the large surface. Any ideas on how I can do this ??

Some ideas I still have to try:

1. If I can somehow extract the Z coordinate of the large surface, I could try to filter based on bubbles that have z < z surface ??
2. If there is a way to “clip” the stuff just in 1 direction (negative Z) from the large surface , this would give me the bubbles that lie underneath.

Any other ideas?

Thanks!

[mwestphal (Mathieu Westphal (Kitware))]

@caladoa

if there is a way to “clip” the stuff just in 1 direction (negative Z) from the large surface , this would give me the bubbles that lie underneath.

Use the Clip filter ?

[caladoa (Andre Calado)]

But what if it is not a plane / sphere/ etc ? If the Clip filter would allow me to select an arbitrary poly mesh to clip from, this might work.

[mwestphal (Mathieu Westphal (Kitware))]

That is not directly possible but this approach should work:

Slice/Clip with a surface

It is possible to slice and clip a volume with a surface by using a Phyton Programmable Filter. This relies on the vtkImplicitPolyDataDistance, so the result is an approximation, not an actual boolean operation. Steps for clip: Open a volume, apply Open a surface, apply In the pipeline browser, click on the volume, then press Ctrl, then click on the surface Add a Programmable Filter Set the output type to vtkUnstructuredGrid Set the script to import paraview.modules.vtkPVVTKExtensionsFilte…

[caladoa (Andre Calado)]

Thanks. I was trying, however not sure how to get the ‘Volume’ representation. I only have unstructured grid and polygonal meshes in my data. How can I create a suitable volume??

[caladoa (Andre Calado)]

bump

[utkarsh.ayachit]

@caladoa

Thanks. I was trying, however not sure how to get the ‘Volume’ representation

You can’t volume render surface mesh. Once you have applied the Contour filter, you have converted that the volumetric data into a surface mesh and hence can’t volume render anymore. You can turn on visibility of the “CellDataToPointData1” filter and the volume render that – not sure if that what you’re intending to do, however. What exactly do you want to volume render in your viz?

[caladoa (Andre Calado)]

I was just trying to follow the steps from @mwestphal . It does complain about the fact that I am giving it a vtk Unstructured Grid and not vtkPolyData…