[vtkusers] MIP & CT-data handling

[Markus Heller]

Dear list members,

I'm trying to use the maximum intensity projection features
of VTK to simulate an X-ray image based on CT-data. 

I tried to modify e.g. the volSimple.tcl example in
the graphics/examplesTcl/ directory, i.e. I changed the
reader from the SLCreader to a vtkImageReader. 
The ImageReader is set to read a few slices from the
Visible Human frozen CT-data set:

vtkImageReader Ireader        
        Ireader SetHeaderSize 3416
    	Ireader SetDataExtent 0 511 0 511 1720  1820 
    	[Ireader GetOutput] SetOrigin 0.0 0.0 0.0
    	Ireader SetDataByteOrderToBigEndian
    	Ireader SetFilePrefix "./VisibleHuman/FrozenCT/c_vm"
        Ireader SetFilePattern "%s%d.fro"
    	Ireader SetDataSpacing 0.9375 0.9375 1.0        
        Ireader Update

It seems that the output from the image reader has not the
data type that the "vtkVolumeRayCastMapper" can handle, since
the following error message is issued:

"The scalar data type: 4 [seems to be vtk short] is not
supported when volume rendering. Please convert the data
to unsigned char or unsigned short."

Now, how could I perform this conversion ??? 


In addition that question, I'd like to know what approaches
other list members use to save modified ct data. There seem
to be some "misalignments" in the VH frozen CT data set. I'd like
to adjust the data for that and save it in the aligned form for
further processing or select and save a volume of interest.


Greetings,


Markus