[vtkusers] Color a point in a 3D volume

Valerie Coffman valerie.coffman at nist.gov
Mon Jul 13 10:32:34 EDT 2009


We've done something similar to what you describe in our software.  We 
need to be able to tint voxels if the user has selected them.  We also 
make voxels transparent if the user has set them to be "inactive".  We 
derived a class from SimpleImageToImageFilter called ResampleImage which 
accomplishes this. 

The objects returned by "GetBitmap" and its methods are specific to our 
project -- they just store which voxels to resample and the color 

The relevant code is :

template <class T>
void ResampleImageExecute(ResampleImage *self, vtkImageData *inData,
              vtkImageData *outData, int extent[6], T* inPtr, T* outPtr)
  int idxX, idxY, idxZ, C=4;
  CColor tint = self->GetBitmap()->getFG();
  double alpha1 = self->GetBitmap()->getTintAlpha();
  double alpha2 = self->GetBitmap()->getVoxelAlpha();
  ICoord temp;
  for (idxZ = extent[4]; idxZ <= extent[5]; idxZ++){
    for (idxY = extent[2]; idxY <= extent[3]; idxY++){
      for (idxX = extent[0]; idxX <= extent[1]; idxX++){
    temp = ICoord(idxX,idxY,idxZ);
    if(self->GetBitmap()->get(&temp)) {
      outPtr[0] = (unsigned 
      outPtr[1] = (unsigned 
      outPtr[2] = (unsigned 
      outPtr[3] = (unsigned char)(255*log(101-100*alpha2)/log(101));
    else {
      outPtr[0] = inPtr[0];
      outPtr[1] = inPtr[1];
      outPtr[2] = inPtr[2];
      outPtr[3] = inPtr[3];

Hope that helps.


VJay wrote:
> I am a newbie to VTK and I am working on volume rendering of DICOM data sets.
> I have successfully volume rendered the input dataset which consisted of
> slices of image data. I wanted to know if I could render a different color
> to each point (x,y,z) in the volume (color it according to my own algorithm)
> and also in the same time set the opacity for each point in the volume i.e.,
> I should be able to access a particular point inside the volume and color it
> (for example lets say red) and also fix the level of opacity for it (say
> 0.3).
> Could you please help me at the earliest ? Thanks a lot.
> Thanks,
> VJ 

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