A simple way to visualize what is happening is with UCSF ChimeraX. You can use
the gaussian filter function to select either the frown or the smile from the
“hidden_frown.map”, and then you can visualize the FFT structure factor
magnitudes for each one – here are the commands to do it -
open hi
Hi James! I’m not sure exactly what cpp4, coot and phenix do for their FFT’s,
but I’m assuming they must mask off the ‘corners’ of the 3D FFT data cube
transform (where the frequency is greater than the Nyquist) during the forwards
transform.
If you take your Cheshire map and do the FFT in mat
