[vtkusers] vtkImageFFT Magnitude

[Randall Hand]

I have a 3D 128^3 volume of data, containing a velocity vector. I use a 
vtkArrayCalculator to extract a single component of the velocity (X in this 
case), and use the vtkImageFFT to compute a Fourier Transform of the data.

The original data is of the range -0.02 to 0.02, but computing the magnitude 
of the resulting FFT dataset yields a minimum value of 6*10^20, and a 
Maximum of over *10^24. Can anyone explain what might be happening here? 
Parseval's theorem states that the resulting FFT should be of similar 
magnitude to the input data.

-- 
Randall Hand
Visualization Scientist
ERDC-MSRC Vicksburg, MS
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