Modelling angle-dependent, spectrally selective glazing

Hi everyone!

I need to model a special coating that changes colour depending on the angle of incident light, in both transmittance and reflectance. Beside this, the system is largely specular. The main goal is to show a realistic appearance of such glazing system under different light and architectural settings.

My first thought was to do some tests with BRTDfunc and the function, as I found some info on that on the forum. I get some odd effects in the resulting images though, like a circular aliasing effect (see image below).

This is the material description I used:

void BRTDfunc film
rrefl grefl brefl
rtrns gtrns btrns
0 0 0
15 0 0 0
0 0 0
0 0 0
4 1.5
1.6 .52 .59 .68

My questions are, am I doing something wrong with modelling a dichroic glass? Once I go ahead with modelling my specific coating, is BRTDfunc the best way to go or are there better alternatives?

Any help is really appreciated! Thank you, Eleonora