[Paraview] Volume rendering RGBA data in Paraview

[David Pont]

I would like to volume render RGBA data derived from digital photographs of serial slices through an object. I found reference on the vtkusers list of this being supported in vtk (vtkFixedPointVolumeRayCastMapper or vtkVolumeTextureMapper3D). I created a legacy vtk file with data represented as STRUCTURED_POINTS. Here is the top of the file:

# vtk DataFile Version 2.0
TreeVol
ASCII
DATASET STRUCTURED_POINTS
DIMENSIONS 1023 1023 10
SPACING    1 1 10
ORIGIN     0 0 0
POINT_DATA 10465290
SCALARS DiscRGBA unsigned_char 4
LOOKUP_TABLE default
255 254 236 0
255 254 236 0
255 254 236 0
255 254 236 0
255 254 236 0
255 254 236 0
255 254 236 0
255 254 236 0
255 254 236 0
255 254 236 0

The file loads without errors, selecting Representation = Slice, Map Scalars = Off shows a single slice in correct RGBA.
But when I select Representation = Volume I get the following error:

Cannot volume render since no point (or cell) data available.

What am I doing wrong? Is volume rendering of RGBA not supported in Paraview? Although I see the Volume Mapper box (greyed out) says Fixed point which indicates vtkFixedPointVolumeRayCastMapper which I understood would handle RGBA. Or is my file format wrong?

regards, Dave

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