Simulating "rough" waveguides

[beniroquai]

This is an awesome project! Thanks a lot for taking so much effort to make it open-source!
I was wondering about two things which may be closely related:

1. Is it possible to introduce "custom" objects like a waveguide with a rough/scattering surface that is a bit more complex by side-loading a numpy matrix of refractive indices
2. What is the easiest way to "export" the refractive indices as a rendered matrix (e.g. 2D numpy array with spatially varying refractive indices)

From what I understand, one has to define the object e.g. waveguide by placing geometrical primitives (e.g. rectangular), but maybe I missed a detail here.

Thanks a lot!