[vtkusers] Re: Texture mapping on a 3D surface.

[Jens Ivar Jørdre]

Hi Goodwin.

I think this is the way to go, although I have some difficulty getting 
the coloring right. The problem I face comes about when I want to 
prepare the MR image volume as the source for vtkProbeFilter.

When I fill an instance of vtkImageData (called fTextureData) with MR 
voxel values I guess I should this info as cell attributes, right? I 
mean the voxel data corresponds to attributes of cells in vtkImage. 
Hence I fill an instance of vtkFloatArray (called textureArray) with 
voxel values and call
fTextureData->GetCellData()->SetScalars(textureArray);

However, the entities whose color I want to determine are points. 
Therfoe I try to use vtkCellDataToPointData in order to determine the 
point attributes in fTextureData. The output from this filter I then 
pipe into vtkProbeFilter. This part of the pipe line looks like this:

vtkCellDataToPointData* ctp = vtkCellDataToPointData::New();
   ctp->SetInput(fTextureData);
   ctp->PassCellDataOn();

vtkProbeFilter* probe = vtkProbeFilter::New();
   probe->SetInput(fPolyData);   // My instance of vtkPolyData
   probe->SetSource(ctp->GetPolyDataOutput());

The result of this is that probe complains about the source being empty. 
  Does anyone see what I'm doing wrong? It kind of looks as if I don't 
use the vtkCellDataToPointData filter properly.

Kind regards
Jens Ivar Jørdre

Goodwin Lawlor skrev:
> Hi Jens,
> 
> Use vtkProbeFilter with your (vtkPolyData) tessellated surface as the input
> and your (vtkImageData) MR image volume as the source. The output will be
> the same vtkPolyData as the input with some point scalar values sampled from
> the source.
> 
> hth,
> 
> Goodwin
> 
> 
> "Jens Ivar Jørdre" <jensivar at fmri.no> wrote in message
> news:42A6ADF7.60600 at fmri.no...
> Howdy.
> 
> Here comes a question from someone who quite recently started using VTK
> 4.2 on Windows XP. So far I've used VTK to visualize a tessellated
> surface of the brain  reconstructed from MR images.
> 
> I then want to move on to color the surface in grey tones according to
> voxel intensities of the surface points. I first tried to use vtkTexture
> to load a (3D) vtkImageData filled with voxel intensities from the MR
> image volume. However, since vtkTexture only supports 2D texture maps I
> had to give up this effort.
> 
> Then I've tried to assign texture coordinates to the points that define
> the tessellated surface, but I see no effect on the surface rendered.
> Does anyone have some example for me to look at? I don't find relevant
> suggestions in the examples shipped with VTK.
> 
> Kind regards
> Jens Ivar Jørdre
> 
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