Guilin Sun
Ansys Employee

The explanation for this script can be found here

Basically it assumes a normal distribution, characterized by rms and corrlation lengths,first in the Fourier space and then transformed into real space. you van refer this example


I would encourage you to try. Once you created the rough surface it is one sample and you can do one simulation. Then you can quantify the reflection and transmission for such assuming periodic rough surface. DIfferent seed can create difference sample. Depending on how do you process the results, you may do a serious of simulations (different samples) and then you can get statistical reuslt.