[Paraview] Odd problem slicing/cutting complex polyhedron

[Andrew Parker]

Hi,

I have attached two files.  One is a single-cell complex polyhedron which I wish to be able to use and visualise (as is, without tessellation and tetrahedralization).  Using 5.5.0 this fails to slice/cut in paraview in any major plane.  Paraview complains about non-manifold (under-connected) edges.  To debug I wrote out as a vtkPolyData containing all the faces of this single cell polyhedron.  This polyData Slices/cuts just fine.  All faces added to the vtp file as VTK_POLYGON, likewise are added as a face-stream when added as a VTK_POLYHEDRON to the vtu file.  To be clear, I write the faces out to the vtp in the same loop I build the faces for the single cell vtu mesh, so they are carbon copies of the faces, including numbering, ordering etc.  I am aware there are more vertices in the file than need be (27 rather than 19), but it was easier...

My working assumption is that there is no problem visualising and working with cells of this type (non-convex) in paraview (real use cases includes a mesh with many of these types of cells).  Clarity on this point would also be good…

I believe paraview should work for concave cells and I suspect it’s a bug (either in paraview or my face-data) because if I use 5.4.1 (or indeed 5.2.0) I can clip the singleCell in the x-plane (with inside-out flag on/off) and I get the expected results. However, in the y and z planes I do not get the expected results and those versions either return an empty result or the whole cell.  I get no results in 5.5.0 regardless of plane.  Finally, I get no results in 5.5.1 either.  So it sort of used to work in earlier versions depending on the plane of slicing, but now does not. 

I’m not sure what I’m doing wrong, can somebody shed some light or spot an error in the attached file?  This may be linked to:

https://gitlab.kitware.com/paraview/paraview/issues/18003

Thanks again,
Andy

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