I'm an italian architect, very happy to help you yo improve this wonderful tool for archicad. In BIM process rendering are a big part of it and the possibilities to use it in the native software it's amazing.
This is a small project for a dentist studio, but a lot it's modeled. I use Archicad to develop the project from the beginning till the building site managment. You will find a lot of documentation in wich you can see all the process.
I hope this file will help you to understand the complexity of the object we need.
In you want more complex o bigger scene tell me, i hope to help you!
I've upload the .pla file on dropbox