CCP4's CMPLFT routine

Nick Blom nick at BCH.UMontreal.CA
Thu Apr 28 13:04:59 EST 1994

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Dear Netters,

I would like to do an FFT on a 3D grid. Since I don't want to be
dependent on base 2 gridsizes I decided to use the CMPLFT routine
supplied by CCP4.

One easy test for any FFT routine is to apply the FFT twice: apart
from a normalization the original function should be returned. 
The CMPLFT returns the original function almost but not completely.
In 3D, each XY plane is inverted in XY and shifted one cell in X 
and one cell in Y; in 2D the same, and in 1D inverted in X and 
shifted one cell.

Now knowing this, one could correct for it after the second FFT, but
because of the application I am working on I like to correct for
it in the Fourier domain. Before I get deep into the source code,
does anyone of you have come across the same problem and has found 
a solution for it? If so, please let me know (a source would be
much appreciated).

Any comments, suggestions and/or different solutions are welcome.


Dr. Nick Blom			    Tel  : +1-514-3436111 ext 5352
Departement de Biochimie	    Fax  : +1-514-3432210
Universite de Montreal		    Email: nick at bch.umontreal.ca
C.P. 6128, Station Centre-Ville
Montreal, PQ, H3C 3J7

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