[vtkusers] [try again]Volume Rendering with RGB values from PPM files

[Naoko TAKAYA]

Dear Vtkusers

I'm trying to reconstruct a 3D volume from PPM files, which 
are slice images of human brain.
I want each resulting voxels to have RGB values from those
PPM files and render the volume using volume raycasting.

I understand that to do volume rendering you use;
vtkPiecewiseFunction  - for opacity
vtkColorTransferFunction  - for volume colors
vtkVolumeProperty  - for setting volume propeties from the two
functions above
vtkVolumeRayCastCompositeFunction
vtkVolumeRayCastMapper
vtkVolume

How do you sepcify colors using vtkColorTransferFunction 
from PPM files read ?
Is this possible using VTK?
If so please tell me how to do it.

I'm using VTK4.0 and Microsoft Visual C++ 6.0.
The brief code is followed.

Any advice is appreciated ;)
Thank you in advance.

Naoko Takaya 
takaya at cv.cs.ritsumei.ac.jp

	vtkPNMReader *vPPM = vtkPNMReader::New();
	vPPM -> SetDataByteOrderToLittleEndian();
	vPPM -> SetFilePrefix("filename.ppm");
	vPPM -> SetFilePattern("filename.ppm.%d");
	vPPM -> SetDataExtent(0,167,0,190,000,100);
	vPPM -> SetDataSpacing(1,1,1);
	vPPM -> SetDataScalarTypeToUnsignedShort();
	vPPM -> Update();
	vtkPiecewiseFunction *vOTFun = vtkPiecewiseFunction::New();
	vOTFun -> AddSegment(0,0,255,1);

	vtkVolumeProperty *vVolProp = vtkVolumeProperty::New();
	
	vtkColorTransferFunction *vClrFun = vtkColorTransferFunction::New();
	vClrFun -> ????????

	vVolProp -> SetColor(vClrFun);
	vVolProp -> SetScalarOpacity(vOTFun);
	vVolProp -> SetInterpolationTypeToLinear();
	vVolProp -> ShadeOn();
	
	vtkVolumeRayCastCompositeFunction *vCFunction =    		vtkVolumeRayCastCompositeFunction::New();
	
	vtkVolumeRayCastMapper *vVolMapper =vtkVolumeRayCastMapper::New();
	vVolMapper -> SetInput(vPPM->GetOutput());
	vVolMapper -> SetVolumeRayCastFunction(vCFunction);
	vVolMapper -> SetSampleDistance(1);

    vtkVolume *vVolActor = vtkVolume::New();
	vVolActor -> SetMapper(vVolMapper);
	vVolActor -> SetProperty(vVolProp);
	vRenderer -> AddProp(vVolActor);