How do I get a Programmable Source to display in Volume representation?
I am following along the example in the ParaView Reference Manual, Section 5.2.4. Reading binary 2D image. The script I am using is basically the same as the example given in the Reference Manual. Why is Volume representation is not available as an option (but Reference Manual Fig. 5.31 shows this same example in Volume representation)?
Output Datatype: vtkImageData
# Code for 'Script'
import numpy as np
# read raw binary data.
# ensure 'dtype' is set properly.
data = np.fromfile("/Users/eckart/Desktop/Paraview/HeadMRVolume.raw", dtype=np.uint8)
dims = [48, 62, 42]
assert data.shape[0] == dims[0]*dims[1]*dims[2], "dimension mismatch"
output.SetExtent(0, dims[0]-1, 0, dims[1]-1, 0, dims[2]-1)
output.PointData.append(data, "scalars")
output.PointData.SetActiveScalars("scalars")
# Code for 'RequestInformation Script'.
executive = self.GetExecutive()
outInfo = executive.GetOutputInformation(0)
# we assume the dimensions are (48, 62, 42).
outInfo.Set(executive.WHOLE_EXTENT(), 0, 47, 0, 61, 0, 41)
outInfo.Set(vtk.vtkDataObject.SPACING(), 1, 1, 1)
One thing that can happen with a Programmable Source is this: if you first click the Apply button with the Output Data Set Type set to something other than vtkImageData, ParaView will evaluate the filter and create a representation (or display) appropriate for that data type. The default output type is vtkPolyData, which does not have a “Volume” representation option.
Now, if you realize your mistake and then change the Output Data Set TypetovtkImageData, you’ll see that your script runs fine, but you won’t be able to find the “Volume” representation. ParaView does not create a new representation for your vtkImageData, but uses the one originally created (this is a deficiency in ParaView, BTW).
The key is to set the correct output dataset type before you click Apply for the first time. Then the representation for vtkImageData with the “Volume” option will be created, and all should work fine.
I had Auto-Apply set in my preferences which seems to cause this issue “automatically”. As soon the Programmable Source is inserted with default output data type vtkPolyData, an Apply is automatically sent which removes the Volume representation permanently.
With Auto-Apply unset, re-inserting the Programmable Source, and changing the output data type to vtkImageData before pressing Apply, Volume representation is now available and working as expected.
