[vtkusers] Possible Bug in vtkXMLReader when reading timeseries

[Cory Quammen]

Simon,

Thanks for your sleuthing and bug report. I don't believe your use case was
known when merge request !488 was merged.

TJ,

Can you have a look at Simon's issue?

Thanks,
Cory

On Fri, Sep 23, 2016 at 12:07 PM, Simon Praetorius <
Simon.Praetorius at tu-dresden.de> wrote:

> I have found an old issue in the mantis bug-tracker addressing this topic:
> #15723
>
> The answer was: "VTK file format does not support saving several time
> steps in a file" and a reference to the file-format description was given.
> This description (version 4.2.) is definitely not complete, thus it can not
> be an indicator for a support of writing timeseries or not.
>
> Although the file-format description does not show support for timeseries,
> at least in older vtk versions (before 6.3) it was supported. The source
> code of the XMLreader shows all the necessary parts to read the
> time-series, all the corresponding attributes are interpreted. The only
> problem is a change in the handling of duplicate names. This was done about
> a year ago in merge request !488. Since there is no test that reads back
> the files generated by `IO/XML/Testing/Cxx/TestXMLCInterface.c` no error
> could be detected. The corresponding test to create the file was removed in
> June 2016.
>
> Thus, the questions are:
> - Is this feature quietly removed from VTK, or removed by accident since
> only few people use it?
> - Is the documentation of the file-format incomplete or the implementation
> simply not cleaned up?
> - Should the test for duplicate array names be rewritten in order to allow
> timeseries again?
> - There should be at least a comment in the file-format description that
> duplicate array names are not allowed!
>
> Maybe this issue could be forwarded to the developer mailing list.
>
> Simon
>
>
> Zitat von Simon Praetorius <Simon.Praetorius at tu-dresden.de>:
>
>
> Hi,
>>
>> When reading a VTK XML-file that includes timesteps, the
>> `vtkXMLDataReader:282` throws an error that multiple arrays with the same
>> name are present in the file. In general this is a valid test and the error
>> is correct, except for the case that multiple timesteps are written in the
>> file. An example file can be created by the test
>> `IO/XML/Testing/Cxx/TestXMLCInterface.c`:
>>
>> ```xml
>> <Piece NumberOfPoints="8" NumberOfCells="1">
>>   <PointData Scalars="example data">
>>     <DataArray type="Float32" Name="example data" TimeStep="0"
>> format="appended" RangeMin="0" RangeMax="0" offset="0" />
>>     <DataArray type="Float32" Name="example data" TimeStep="1"
>> format="appended" RangeMin="1" RangeMax="1" offset="240" />
>>     <!-- ... -->
>>   </PointData>
>> </Piece>
>> ```
>> Here all DataArrays refer to the same dataset at different timesteps.
>>
>> Reading back this file, using a `VTLXMLUnstructuredGridReader` (e.g.
>> `Examples/IO/Cxx/DumpXMLFile.cxx`), produced the error above:
>>
>> ```
>> vtkXMLDataReader.cxx, line 282: Duplicate array names.
>> ```
>>
>> Writing TimeSteps seems to be supported by the XMLReader and the
>> XMLWriter. Maybe the `vtkXMLWriterC` is not valid/compatible any more? Is
>> the structure of the vtk format changed when writing timeseries, compared
>> to the xml-code shown above?
>> (I'm referring to the VTK version 7.0.0, when naming line-numbers.)
>>
>>
>> This issue refers to an old ParaView issue #5542 (
>> http://www.paraview.org/Bug/view.php?id=5542). The file was readable
>> with at least vtk-5.2 and paraview-3.6.2.
>>
>> Simon
>>
>> --
>> Dr. Simon Praetorius
>> Institut für Wissenschaftliches Rechnen
>> Fachrichtung Mathematik
>> Technische Universität Dresden
>> Tel.: TUD-42377
>> Mail: simon.praetorius at tu-dresden.de
>> Web: www.math.tu-dresden.de/~spraetor
>>
>
>
>
> --
> Dr. Simon Praetorius
> Institut für Wissenschaftliches Rechnen
> Fachrichtung Mathematik
> Technische Universität Dresden
> Tel.: TUD-42377
> Mail: simon.praetorius at tu-dresden.de
> Web: www.math.tu-dresden.de/~spraetor
>
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-- 
Cory Quammen
Staff R&D Engineer
Kitware, Inc.
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