Hi,

On Linux I can install eigen with various backends, including FFTW.

On MacOS (Sierra), after installing the same latest FFTW software in the same default directory ("/usr/local"), cmake can't find FFTW: "Could NOT find FFTW (missing: FFTW_LIBRARIES)"

In general, even on Linux I can't setup custom locations (using env variables as shown in "FindFFT.cmake" file), it works only with default locations.

Any help will be appreciated.

You need to define the cmake FFTW_LIBRARY and FFTW_INCLUDE_DIR variables:

cmake . -DFFTW_INCLUDE_DIR=... -DFFTW_LIBRARY=...

those are not environment variables.