I'm looking for a subroutine of Fortran90 about "Fast Fourier
Transform of a Step-function in 3-dimonsional."
I read the related subroutines in Numerical Recipes Book, but I
couldn't match it for a 3D step function.
Whould you please let me to have access to a subroutine for mentioned
goal? I don't know how I should match this subroutine between 3D step
function and FFT.

I'm anxiously looking forward your reply.

Kind Regards,
Fatemeh

Fatemeh wrote:

The Fourier transform is separable in rectangular coordinates.

Does that help?

-- glen

On Jun 23, 2:26 am, glen herrmannsfeldt ugcs.caltech.edu> wrote:

This is more a question for a numerical analysis newsgroup such as
sci.math.num-analysis since it's not Fortran-specific. (In fact, the
latest edition of Numerical Recipes abandons Fortran altogether in
favor of C++).