ParaView: Mixed definition of unstructured zone by elements and by faces is not valid

[dbgarlisch]

I found this 1 year old CGNS discussion and a similar 2 year old ParaView discussion.

As best I can tell, CGNS/SIDS does NOT prohibit mixed element/face zones.

Am I correct in saying that it is the ParaView CGNS reader that is imposing this limitation?

I don't know of any reason why a reader shouldn't be able to handle mixed element/face zones. It might be a little more work/bookkeeping; but doable.

I have generated mixed element/face zones meshes that load into CGNSview and pass CGNScheck (v3.31) without objection.

I know polyhedron/polygon encoding changes in v4. Is this a restriction new to v4?

I am looking for official guidance on what a valid CGNS export should be for a mesh volume zone that contains both canonical and polyhedron elements...

Do I split out the polyhedron and canonical cells into different zones with the same VC?
Do I write all canonical cells as polyhedron?
Other?

Or is this a practical issue? Since many/most/all readers will most likely balk on a mixed element/face zone, I should play it safe and export a uniform file?

Whatever the official answer, the SIDS and related docs should be amended to make this clear.

[brtnfld]

FYI, VisIt https://wci.llnl.gov/simulation/computer-codes/visit if you want to see if it can read the file.

[dbgarlisch]

The ParaView messages for HemisphereInBox-Poly.zip:

ERROR: In vtkCGNSReader.cxx, line 2471
vtkCGNSReader (000001F4A6F9FE10): Mixed definition of unstructured zone by elements and by faces is not valid.

ERROR: In vtkCGNSReader.cxx, line 4713
vtkCGNSReader (000001F4A6F9FE10): Error Reading file

ERROR: In vtkExecutive.cxx, line 741
vtkPVCompositeDataPipeline (000001F4A694FBA0): Algorithm vtkCGNSFileSeriesReader (000001F4A6950920) returned failure for request: vtkInformation (000001F4B8765A30)
Debug: Off
Modified Time: 457447
Reference Count: 1
Registered Events: (none)
Request: REQUEST_DATA
FORWARD_DIRECTION: 0
ALGORITHM_AFTER_FORWARD: 1
FROM_OUTPUT_PORT: 0

The TET (red) and PYRAMID (yellow) cells in the transition regions between the HEX (blue) cells are converted to polyhedra when exported to the CGNS file. The hex cells with faces touching the transition pyramids are also converted to polyhedra. The resulting mesh is fully point matched (no hanging nodes).

[dbgarlisch]

I misspoke earlier. Due to recent Fluent export changes, the ParaView Extract Cells by Type filter is no longer crashing.

However, after importing a Fluent cas version of the mesh, the polyhedron cells do not display when the filter is activated.