How can I render redirection of metal blinds with radiance

Recently I was reading “daylight simulation with photon map” wrote by Roland Schregle, and found a rendering picture of Y glass’ redirection as following,


I also want to render the redirection of metal blinds referring to the example, is there anyone who have the example files of Y glass’ redirection rendering or could provide some suggestions?

I tried to model the incident beam using a spotlight but I can never get the beam as shown in the picture.

Thank you!