[Paraview] VTK XML binary file format

[Peter Bastian]

Olivier Magotte schrieb:
> Peter Bastian wrote:
> 
>> Hi all,
>>
>> I am trying to write VTK XML unstructured grid files (.vtu) by myself
>> (i.e. without using vtkXMLUnstructuredGridWriter). Ascii works fine but
>> binary makes problems. I followed the instructions given previously on
>> this list, i.e. I use inline DataArrays, put the size of the data in
>> front of the block and encode everything base64.
>>
>> Now there are two problems:
>>
>> 1) The "offsets" array causes an error when reading:
>>
>> peter at cray:~/FE/dune-dd$ paraview
>> ErrorMessage
>> # Error or warning: There was a VTK Error in file:
>> /home/amy/ParaViewReleaseRoot/paraview-2.4.1/VTK/IO/vtkXMLUnstructuredDataReader.cxx
>>
>> (592)
>> vtkXMLUnstructuredGridReader (0x8dfacb0): Cannot read cell connectivity
>> from Cells in piece 0 because the "offsets" array is not monotonically
>> increasing or starts with a value less than 1.
>> ErrorMessage end
>>
>> When I write only the offsets array in ascii, the file is read without
>> error message. This is curious because all the writing is done by one
>> class in my code. I also checked the encoded binary data and it looks OK.
>>
>> 2) Loading the file with all in binary except the "offsets" array, the
>> point data as well as the cell data and the point positions are not
>> correct.
>>
>> Now my question:
>>
>> Is there some further undocumented magic (like the size in bytes at the
>> beginning) that I have to consider?
>>
>> I would prefer to write VTK files without linking in VTK itself.
>> In the attachment I append binary and ascii versions of my file.
>>
>> Thanks for any response.
>>
>> -- Peter
>> ------------------------------------------------------------------
>> Peter Bastian, IWR,Uni Heidelberg, INF 348,R 020, 69120 Heidelberg
>> email: Peter.Bastian at iwr.uni-heidelberg.de   Tel: +49 6221 54 4984
>> WWW: http://www.iwr.uni-heidelberg.de/~Peter.Bastian Fax: ... 8860
>>  
>>
> I suggest to encode the data array size (4 bytes) first and then encode
> the array (two '=' character must appear after the first 6 characters).
> It works for me.
> 
> Useful information can also be found here:
> http://public.kitware.com/pipermail/paraview/2005-April/001391.html
> 
> Olivier
> 
Strange. This does not work at all. Does not give an error message, but
the mesh then has 0 cells and 0 vertices. Also, it is in contrast to the
reference you have sent. I use uncompressed data.

Thanks anyway.

-- Peter
------------------------------------------------------------------
Peter Bastian, IWR,Uni Heidelberg, INF 348,R 020, 69120 Heidelberg
email: Peter.Bastian at iwr.uni-heidelberg.de   Tel: +49 6221 54 4984
WWW: http://www.iwr.uni-heidelberg.de/~Peter.Bastian Fax: ... 8860