[Paraview] VTK parallel unstructured grid and halo elements

[Berk Geveci]

Hi Louie,

Ghost/halo nodes are considered valid (but duplicated) so they are taken
into account when calculating ranges, statistics etc. What you need is to
mark them as invalid, it sounds like? We are making slow progress towards
having an infrastructure that supports this but currently it is only
partially support for structured grids and AMR meshes and a subset of
filters.

Best,
-berk

On Wed, Feb 25, 2015 at 11:06 AM, Louie Cardone-Noott <
louie.cardone-noott at linacre.ox.ac.uk> wrote:

> 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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