[Paraview] VTK parallel unstructured grid and halo elements

[Louie Cardone-Noott]

Hi again list,

Inspired by David Ortley's recent success (see "Smooth seams in SILO
files") I wonder if perhaps the way I'm doing it is correct, but Paraview
is incorrectly considering the values at hidden nodes when calculating data
ranges.

Essentially my "option 3" (writing a vtkGhostLevels array) appears to work
as it should, and the "seams" are hidden in my parallel data. But, if I
then Extract Surface and look at the Data Arrays -> Data Ranges I see
values which can only be from non-surface nodes. I suspect they are
probably from nodes on the (hidden) interior surfaces. This is obviously a
bug.

I could probably provide a minimal example if useful.

Best wishes,
Louie


On 17 January 2015 at 16:26, Louie Cardone-Noott <
louie.cardone-noott at linacre.ox.ac.uk> wrote:

> Hi Paraview list,
>
> I use a finite element code that generates VTK output, but I'm having
> trouble dealing with halo (ghost) nodes/elements correctly.
>
> We currently partition meshes node-wise, and each process writes all its
> owned nodes and one level of halo nodes to a chunk. Once all the chunks are
> loaded there is a "double layer" of internal boundaries between processes.
> I'd really like to be able to use the Extract Surface filter correctly but
> as you would expect it also finds all the internal surfaces. From searching
> I've tried:
>
> * Clean To Grid, but this removes both sides of the double layer leaving
> unsightly gaps.
> * Writing a vtkGhostPoints array (on nodes) but this seems not to be used
> by this filter (or Paraview at all?)
> * Writing a vtkGhostLevels array (on elements). This correctly hides all
> the ghost elements at the internal boundaries (great!) but still doesn't
> let me do everything I want to. For example, the extracted surface looks
> right, but the array limits still seem to be based on the max/min of the
> external AND internal surfaces, so I suspect the internal ones are just
> "hidden from view".
>
> What's the right way to deal with this?
>
> Thanks in advance.
>
> Louie
>
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