Hi All,
I guess last time I posted this question the image file did not attach
correctly. I apologize for re-posting so late. I have not see a response, so I
am re-posting the question. 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 texture line is 512 elements long so
their shouldn't be any interpolation.
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 0.004. The cut-off value was set so only the FFT of
the first and second frequencies are not set to zero. The first frequency
corresponds to the mean and therefore after inverting the fft back, only the
second frequency should result in the waviness. What is interesting is that
Gwyddion is showing a smaller frequency than matlab, but I don't understand how
this is possible. Any suggestions? Maybe the x trace used to calculate the fft
for the texture line is different internally than what can be exported through
the gwyddion gui?
--
Casey LaMarche
Postdoctoral Researcher
Hrenya and Weimer Research Groups
UCB 596
D1B28/D1B50
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