[vtkusers] vtkUnstructuredGridWriter only stores 6 digits?

[Nishad Sohoni]

Hi Nico,

I can confirm that I see the same behavior. I added the following lines 
to the end of your script:

'''
rdr = vtk.vtkUnstructuredGridReader()
rdr.SetFileName('test.vtk')
rdr.Update()
loc = rdr.GetOutput()
pts = numpy_support.vtk_to_numpy( loc.GetPoints().GetData() )
print pts
print pts.dtype
'''
and regardless of whether I called writer.SetFileTypeToASCII(), the 
dtype was always float64, but there was a loss in precision.

If you can get away with writing a binary file, might I suggest using 
vtkXMLUnstructuredGridWriter? With the above code, python printed with 
the correct precision and dtype (obviously changing to 
vtkXMLUnstructuredGridReader).

Cheers,
Nishad.


On 17/12/2015 10:40, Nico Schlömer wrote:
> This smells very much like the vtk_array data being interpreted as 
> single precision even though
> ```
>   Data type: double
> ```
> Cheers,
> Nico
>
> On Thu, Dec 17, 2015 at 2:23 AM Nico Schlömer 
> <nico.schloemer at gmail.com <mailto:nico.schloemer at gmail.com>> wrote:
>
>     Hi everyone,
>
>     with
>     ```
>     import numpy
>     import vtk
>     from vtk.util import numpy_support
>
>     mesh = vtk.vtkUnstructuredGrid()
>
>     # add points to mesh
>     points = numpy.array([
>         [0.123456789, 3.14159265, 0.0]
>         ])
>     vtk_points = vtk.vtkPoints()
>     vtk_array = numpy_support.numpy_to_vtk(points)
>     vtk_points.SetData(vtk_array)
>     mesh.SetPoints(vtk_points)
>
>     # write to VTK
>     writer = vtk.vtkUnstructuredGridWriter()
>     writer.SetFileTypeToASCII()
>     writer.SetFileName('test.vtk')
>     writer.SetInputData(mesh)
>     writer.Write()
>     ```
>     I noticed that, although the `point` is given with some precision,
>     the output `test.vtk` file only contains 6 digits of accuracy,
>     ```
>     0.123457 3.14159 0
>     ```
>     The numpy data type hosts 8 digits.
>
>     Is this a bug or expected? How to mitigate?
>
>     Cheers,
>     Nico
>
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
>
> Search the list archives at: http://markmail.org/search/?q=vtkusers
>
> Follow this link to subscribe/unsubscribe:
> http://public.kitware.com/mailman/listinfo/vtkusers
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://public.kitware.com/pipermail/vtkusers/attachments/20151217/1c4218ce/attachment.html>