[Paraview] Increase number of slices for volume rendering ...

[Alvaro Sanchez]

Hi Niklas,

unfortunately sampling distance is currently not exposed as a UI setting.
You could make the
following changes in order to decrease the sampling distance,

VTK/Rendering/VolumeOpenGL2/vtkSmartVolumeMapper.cxx
ln. 91 -- comment
<https://gitlab.kitware.com/vtk/vtk/blob/master/Rendering/VolumeOpenGL2/vtkSmartVolumeMapper.cxx#L91>
//  this->GPUMapper->LockSampleDistanceToInputSpacingOn();

/ParaViewCore/ClientServerCore/Rendering/vtkImageVolumeRepresentation.cxx
ln. 350 -- add
<https://gitlab.kitware.com/paraview/paraview/blob/master/ParaViewCore/ClientServerCore/Rendering/vtkImageVolumeRepresentation.cxx#L350>
  this->VolumeMapper->SetAutoAdjustSampleDistances(0);
  this->VolumeMapper->SetInteractiveAdjustSampleDistances(0);
  const float dist = 1.0;
  this->VolumeMapper->SetSampleDistance(dist);  //<-- smaller dist for
higher quality / worse performance

This is a hack, but it should improve the rendering quality.  Be careful
however to not make 'dist'
too small as this hack has the disadvantage that the specified sampling
distance would be also
used during interaction (you might notice some performance issues).

If you are trying to increase the sampling rate in order to reduce "wood
grain" artifacts, you
could instead try enabling jittering, this might also help (without major
performance concerns),

VTK/Rendering/VolumeOpenGL2/vtkSmartVolumeMapper.cxx

ln. 92 -- add
<https://gitlab.kitware.com/vtk/vtk/blob/master/Rendering/VolumeOpenGL2/vtkSmartVolumeMapper.cxx#L92>
  this->GPUMapper->UseJitteringOn();

We are planning to expose both settings in the future so that they can be
controlled through
the UI in ParaView.

Hope that helps,
Álvaro


On Tue, Jan 17, 2017 at 11:58 AM, Niklas Röber <roeber at dkrz.de> wrote:

> Hi,
>
> for GPU based volume rendering, is there a way to increase the number of
> slices to enhance the overall quality of the rendering? If this can not
> directly be done in the GUI, would it be possible to adjust a scaling
> factor in the code?
>
> Thanks and Cheers,
> Niklas
>
>
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-- 
Alvaro Sanchez
Kitware, Inc.
Senior R&D Engineer
21 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-881-4901
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