[Paraview] Writing XML VTK Binary files from C++

[Stegmeier, Nicholas]

Hello,


Thank you both for your advice. I will be sure to pursue both options and see if I can get them working.


Thank you again,

Nicholas Stegmeier

________________________________
From: David E DeMarle <dave.demarle at kitware.com>
Sent: Friday, December 1, 2017 8:35:45 AM
To: Mark Olesen
Cc: Stegmeier, Nicholas; paraview at paraview.org
Subject: Re: [Paraview] Writing XML VTK Binary files from C++

Another approach is to use VTK itself to write the files.

Since VTK 6 it is straightforward to configure a VTK build consisting
of only the IO/ParallelXML module and its required dependencies. To do
so, in cmake, turn of testing, all groups and turn on
Module_vtkIOParallelXML, and you should be set.

David E DeMarle
Kitware, Inc.
Principal Engineer
21 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-881-4909


On Fri, Dec 1, 2017 at 2:34 AM, Mark Olesen <Mark.Olesen at esi-group.com> wrote:
> When you say "writing binary", you need to distinguish between three
> possibilities.
> 1) writing binary "inline" (actually base64 encoded)
> 2) writing binary "append" (actually base64 encoded)
> 3) writing raw binary "append" (really raw binary)
>
> Since you already have ASCII writing working and its content is "inline", it
> won't take much more to get binary inline working.
> By "inline", I mean when the output is placed between the <xxx> </xxx>
> markers. Eg,
>     <DataArray ...>
>         content
>     </DataArray>
>
> For the binary case, the content is written as base64-encoded data, which
> means that your output writer for these sections needs to pass the content
> through a base64 layer to do the encoding for you.
>
> If it helps as reference, we have the same thing in OpenFOAM, except that we
> only write vtu and vtp files (we don't have rectilinear meshes).
>
> In the repo https://develop.openfoam.com/Development/OpenFOAM-plus
> we have a foamVtkBase64Formatter and a foamVtkBase64Layer (both under
> src/fileFormats/vtk/format/) that add a base64Layer to encode and output as
> base64 (src/OpenFOAM/db/IOstreams/hashes/base64Layer.[CH]).
>
> You'll see that the foamVtkBase64Layer and base64Layer are quite low level
> means of adding an tiny encoding buffer (3 chars size) to intercept output
> prior to sending through to a std::ostream. It take very little effort to
> adopt for your output and thus quite easy to drop in instead of your current
> ASCII outputter.  For it too work easily, however, you should make sure that
> you need to generate your output content with a write() method instead of
> using '<<'. This allows somewhat easy switching between something like a
> foamVtkAsciiFormatter and the binary version, but more importantly it makes
> it easier to track the output state.
>
> When browsing through the code, you may also notice that we have support for
> writing in appended format (raw and base64). However, I would not advise you
> to tackle that immediately. There are a few more things to watch out for
> here, but more importantly it will change many more things on the calling
> side.
>
> I hope this information helps you.
> /mark
>
> --
> Dr Mark OLESEN
> Principal Engineer, ESI-OpenCFD
> ESI GmbH | Einsteinring 24 | 85609 Munich | GERMANY
> www.openfoam.com<http://www.openfoam.com> | www.esi-group.com<http://www.esi-group.com> | mark.olesen at esi-group.com
>
>
> On 11/30/17 18:00, Stegmeier, Nicholas wrote:
>>
>> Hello,
>>
>> I am new to Paraview and C++ coming from a mostly mathematics background.
>> I am emailing to get resources or help on writing binary XML VTK files from
>> C++.
>>
>> I have finally succeeded in using the ASCII XML VTK format for a 2D
>> rectilinear CFD application. My ".pvtr" file is shown below.
>>
>> How can I write this file and my other XML VTK files in binary from C++?
>> Do I need a special C++ library?
>
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