[Gwyddion-users] reproducing waviness

[Casey LaMarche]

Hi All,

I am working on reproducing the waviness calculated in the ISO function
of Gwyddion. I am looking to calculate the wavelength parameters for the
entire surface via matlab. However, I am hitting a wall correctly
reproducing the waviness calculated in Gwyddion. I have spent several
days looking at the source code and am still missing something. Anyone
have any luck doing this? I am wondering if perhaps Matlab and C++ have
different libraries for calculating the FFT?

The bulk of the source code related to the waviness calculation is in
the roughness.c file (modules/tools/roughness.c) and runs from
approximately lines 1449 - 1576, however there are a few functions
called from other files. I don't know how much detail to get into here,
but some help would be great. Of course I will share the matlab code to
calculate the wavelength features for the entire surface with the list
once this problem is solved.

Below is a comparison of the waviness calculated from Matlab and
Gwyddion for a texture line with cutoff 0.001.