How can a diffused(frosted) glass be modelled in path tracing How can a diffused(frosted) glass be modelled in path tracing?

Currently I am able to define a window poly line as a clear glass material where it transmits or reflects the ray. I am not clear though how it should work if the sheet of glass is frosted(diffuse transmission?).
Assuming that you are familiar with the concept of BSDFs, the usual way of modelling rough dielectric surfaces (i.e. glass, water, plastics) is to use microfacet-based models like Microfacet Models for Refraction through Rough Surfaces.

To make it work efficiently in a path tracer you will need a good sampling strategy, like Importance Sampling Microfacet-Based BSDFs using the Distribution of Visible Normals.

Also keep in mind, that the mentioned BSDF model tends to get darker as you increase roughness because it neglects the light which gets inter-reflected among micro-facets. This can be compensated, but it's not a trivial thing to do.