[vtkusers] Questions about unsigned char scalars

Mario Biondini Mario_Biondini at ndsu.nodak.edu
Fri Oct 13 11:59:48 EDT 2000

I am running a program designed for volume rendering. Within the program
I have this code:

  // Create a structure point dataset

  vtkStructuredPoints *vol = vtkStructuredPoints::New();
      sp = 1.0;
      vol->SetSpacing(sp, sp, sp);

// Creat a scalar and read the scalar data from file

  vtkScalars *scalars = vtkScalars::New();
  for (k=0; k<45; k++)
     kOffset = k * 76 * 49;
     for (j=0; j<49; j++)
        jOffset = j * 76;
        for (i=0; i<76; i++)
          in1 >> s;
          offset = i + jOffset + kOffset;

// Input the scalar data into the Structure Point Data Set


  // Create the volume mapper and set the ray function and scalar input

  vtkVolumeRayCastMapper *volumeMapper = vtkVolumeRayCastMapper::New();

At execution time I get the following error

ERROR: In vtkVolumeRayCastMapper.cxx, line 921
vtkVolumeRayCastMapper (0x82b3ab0): The scalar data type: 10 is not
supported when volume rendering. Please convert the  data to unsigned
char or unsigned short.

Reading Schroeder, Martin and Lorensen book the Visualization Toolkit
(2nd Edition) I noticed than in version 2.0 of VTK there was a function
called vtkUnsignedCharScalars to creat scalars of the type unsigned
char. This function however is not availabe in verson 3.1.

Question: is there an error in my code? and how do I create scalars that
are if type unsigned char?

Mario Biondini, Ph.D.
Department of Animal and Range Sciences
North Dakota State University
Fargo, ND 58103
Phone: (701) 231-8208
Fax: (701) 231-7590
e-mail: Mario_Biondini at ndsu.nodak.edu

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