Trying to generate sun rays falling into a room

Hi - I’m trying to generate sun rays falling onto the inside of my models Room faces.

I have this so far:

But really stuck now and not sure if I’m even on the right track. I’ve tried looking at other blogs - and nothing seems to tie what I’m after together…any help woudl be really appreciated - if only putting me on the right track.

Sun Rays.dyn (12.5 KB)