[Paraview] XDMF Set

Thu May 28 23:20:35 EDT 2015

Responses in line.

On Thu, May 14, 2015 at 4:47 AM, Chris Richardson <chris at bpi.cam.ac.uk>
wrote:

>
> I guess that leads to the following questions:
>
> 1) When will Xdmf3 be used by ParaView?
>
>
I want to deprecate Xdmf2 and make Xdmf3 the default the next release.
Because Xdmf3 adds a dependency on boost Xdmf will have to become optional
in ParaView. The Kitware binaries will have it on because we already
Superbuild in boost for the VisItBridge, but other versions could easily
drop it.

> 2) Does 2D work properly?
>
>
I don't think I tested that particular path in Xdmf3.  If you can make a
small test dataset which disproves its working, I'll likely be able to fix
it and add it to the regression test suite for Xdmf3 in VTK.

> 3) What about Attributes which are not in a "Set". The XDMF pages say
> this:-
>
> "A Grid centered Attribute might be something like "Material Type" where
> the value is constant everywhere in the grid. Edge and Face centered values
> are defined, but do not map well to many visualization systems."
>

> But how do you define Edge and Face centered values for the whole mesh,
> anyway?
>
>
Not sure I understand the question, much less the answer, but lets have a
go shall we?
Set's can have their own attributes and those attributes can be grid
centered. So if the set has all the edges, then the set's grid centered
attributes apply to all of the edges in the mesh.

> 4) Finally, is there any real need (in the case below) to go via the
> Faces? Maybe, before the standard gets more widespread, this could be
> eliminated,
>    and just go direct from Cell->Edge... OK, this is just a suggestion...
>
>
Could do. I can't think of a reason off the top of my head why vtk's
cell->GetEdge is any less well defined than cell->GetFace()->GetEdge() and
it is probably faster. Maybe that is why the "bug" is there in xdmf1/2.

> Chris Richardson
> BP Institute
> Madingley Road
> Cambridge CB3 0EZ
>
>
> On 14/05/2015 01:28, David E DeMarle wrote:
>
>> I believe in this case the intent was to get the edge'th edge out of
>> the face'th face out of the cell'th cell.
>>
>> So in your example we get four edges out.
>>
>> cell 0's 0'th face's 0'th edge,
>> cell 0's 1'st face's 1'st edge,
>> cell 1's 2'nd face's 0'th edge,
>> and
>> cell 1's 3'rd face's 2'nd edge.
>> The ordering in each case is defined by VTK.
>>
>> However, in the code (specifically vtkXdmfHeavyData.cxx:1507) it looks
>> like it does exactly as you say.
>> This appears to be a bug.
>>
>> In the Xdmf3 version  we do it properly (see
>> vtkXdmf3DataSet.cxx:2205).
>>
>> David E DeMarle
>> Kitware, Inc.
>> R&D Engineer
>> 21 Corporate Drive
>> Clifton Park, NY 12065-8662
>> Phone: 518-881-4909
>>
>> On Fri, Apr 17, 2015 at 5:39 AM, Chris Richardson
>> <chris at bpi.cam.ac.uk> wrote:
>>
>>  I would like to be able to specify data, or subsets of data in the
>>> XDMF
>>> format with Edge or Facet sets.
>>>
>>> According to the header file of XdmfSet.h:
>>>
>>> XdmfSet is a Class that handles sets of nodes,cells,faces, and
>>> edges
>>> on an XdmfGrid. They may be centered on the Node, Edge,
>>> Face, Cell. An XdmfSet can have from 1 to 3 DataItems. The
>>> last DataItem
>>> is always the "Ids" or the indexes into Nodes, Cells, etc.
>>> If SetType is
>>> "Face" or "Edge", the First DataItem defines the CellIds.
>>> If SetType is
>>> "Edge" second DataItem defines FaceIds
>>>
>>> I have two questions:
>>>
>>> 1) What is the purpose of the FaceIds for a set of Edges?
>>>
>>> From what I can tell, using ParaView, the three dataitems provide:
>>> global CellIDs, unused FaceIDs, cell-local EdgeIds
>>>
>>> e.g. in this case, the first DataItem "0 0 1 1" lists the cells,
>>> the second DataItem "0 1 2 3" is ignored, and the third
>>> DataItem "0 1 0 2"
>>> lists the cell-local Edges which have data attached?
>>>
>>> <Set SetType="Edge" Name="edgeSet">
>>> <DataItem NumberType="Int" Dimensions="4" Format="XML">
>>> 0 0 1 1
>>> </DataItem>
>>> <DataItem NumberType="Int" Dimensions="4" Format="XML">
>>> 0 1 2 3
>>> </DataItem>
>>> <DataItem NumberType="Int" Dimensions="4" Format="XML">
>>> 0 1 0 2
>>> </DataItem>
>>> <Attribute Name="Set Values" Center="Edge">
>>> <DataItem Format="XML" Dimensions="4">
>>> 100 200 400 600
>>> </DataItem>
>>> </Attribute>
>>> </Set>
>>>
>>> Is that correct?
>>>
>>> 2) How can I specify an Edge set in 2D? Nothing seems to work in
>>> this case,
>>> as ParaView complains that the cells have invalid Faces.
>>>
>>> --
>>> Chris Richardson
>>> BP Institute
>>> Madingley Road
>>> Cambridge CB3 0EZ
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>>
>>
>>
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>
> --
> Chris Richardson
> BP Institute
> Madingley Road
> Cambridge CB3 0EZ
>
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