[vtkusers] How to acces to gradient data in a volume mapper

[vincent elkouby]

Hello,

some one does know how to access to gradient data in a vtkVolume Mapper?

I use a vtkFixedPointVolumeRayCastMapper. This class compute the volume gradient to render the volume. But I would like to access to the gradient data to filter it. There is to methods to get attributes from this class named: 

      unsigned short **gradNormal=volMapper->GetGradientNormal();
      unsigned char **grad       =volMapper->GetGradientMagnitude();

But it's doesn't work or I don't know how it works. The both pointers are null.

PS: My soft is working.



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