|Substance Rain System.
NOTE: You must have Substance Player or the free Substance plugin for 3dsmax, to play with: https://www.allegorithmic.com/buy/download.
My first version of the rain system.
You must have a side with standard glass and the wet side with the rainy glass as in the example below.
As it is a PBR system, you must have roughness checked in both reflection and refraction slots.