Optics Experiments on the Cheap

This video shows a simple way to test your optics for solar reflectors before you make them. I tried (and failed) to find software to do this.
Perhaps it is a good thing that I failed!
You can find info about compound parabolics at
http://www.fossilfreedom.com/increase-output.html
and at
http://www.appropedia.org/Understanding_Solar_Concentrators
and perhaps you could test out some of the designs they show with this simple technique!
Brian White