[vtk-developers] Volume rendering implementation

[Julien Finet]

Hi Sason,

VTK has CPU and GPU implementations for raycasting volume rendering. For
more information about the GPU ray cast mapper, you can read July 2008
edition of The Source:
http://www.kitware.com/products/archive/kitware_quarterly0708.pdf (the
mapper was previously in VTKEdge but is now in VTK).

Some doxygen doc:
http://www.vtk.org/doc/nightly/html/classvtkFixedPointVolumeRayCastMapper.html
http://www.vtk.org/doc/nightly/html/classvtkGPUVolumeRayCastMapper.html
http://www.vtk.org/doc/nightly/html/classvtkSmartVolumeMapper.html

Hope this helps,
Julien.

On Mon, May 9, 2011 at 9:31 AM, Sason Ohanian Saki <sason at kth.se> wrote:

> Hi!
>
> I am wondering If anyone knows how volume rendering with ray casting is
> implemented in VTK? Is it a software implementation or hardware-accelerated
> with shaders?
>
> Thanks!
>
> /Sason
>
> 7 maj 2011 kl. 23.25 skrev David Gobbi:
>
> > The only way that I know of is to get the range directly from the
> scalars,
> >
> > double range[2];
> > data->GetPointData()->GetScalars()->GetRange(range, component);
> >
> > Personally, I would not be opposed to changing vtkDataSet::ComputeRange()
> > so that it computed the range over all components.
> >
> >  David
> >
> >
> > On Sat, May 7, 2011 at 1:37 PM, Nicolas Rannou
> > <Nicolas_Rannou at hms.harvard.edu> wrote:
> >> Hi David,
> >>
> >> Thanks for the clarification.
> >> Which is the best practice to get the scalar range of each component
> then?
> >>
> >>
> >> On May 6, 2011, at 5:53 PM, David Gobbi wrote:
> >>
> >>> Hi Nicolas,
> >>>
> >>> The GetScalarRange() method computes the scalar range of the first
> component.
> >>>
> >>> - David
> >>>
> >>>
> >>> On Fri, May 6, 2011 at 3:00 PM, Nicolas Rannou
> >>> <nicolas_rannou at hms.harvard.edu> wrote:
> >>>> Hello,
> >>>>
> >>>> I'm experiencing a strange behavior in VTK which might be a bug.
> >>>> It took me a while to locate the issue:
> >>>>
> >>>> if I create a LUT with a NULL red component:
> >>>>   iRed = 0;
> >>>>   iGreen = 255;
> >>>>   iBlue = 255;
> >>>>   iAlpha = 255;
> >>>>   double iRange[2] = {0, 255};
> >>>>
> >>>>   vtkSmartPointer<vtkLookupTable> lut =
> >>>>       vtkSmartPointer<vtkLookupTable>::New();
> >>>>   double* HSV = vtkMath::RGBToHSV(iRed,iGreen,iBlue);
> >>>>   lut->SetAlpha(iAlpha);
> >>>>   lut->SetHueRange(HSV[0], HSV[0]);
> >>>>   lut->SetSaturationRange(1, 1);
> >>>>   lut->SetValueRange(0, 1);
> >>>>   lut->SetRange(iRange);
> >>>>   lut->Build();
> >>>>
> >>>> I color my image with this LUT:
> >>>>
> >>>>   vtkSmartPointer<vtkImageMapToColors> coloredImage =
> >>>>       vtkSmartPointer<vtkImageMapToColors>::New();
> >>>>   coloredImage->SetLookupTable(iLUT);
> >>>>   coloredImage->SetInput( iImage );
> >>>>   coloredImage->PassAlphaToOutputOff();
> >>>>   coloredImage->SetOutputFormatToRGB();
> >>>>   coloredImage->Update();
> >>>>
> >>>> then:
> >>>>   double* range = coloredImage->GetOutput()->GetScalarRange();
> >>>> returns [0,0].
> >>>> then everything I do with this image is messed up...
> >>>>
> >>>> If iRed != 0, the scalar range of the "coloredImage" will be correct
> then my
> >>>> pipeline is working.
> >>>>
> >>>> Am I doing something wrong?
> >>>>
> >>>> Thanks,
> >>>>
> >>>> Nicolas
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