your just going to end up with light activated motor speed controller i made i mouse robot with a circuit just like that it headed for the light worked real good the only thing defferant is the 1 k I used a variable resistor for it.
"Sketchup" will make images like that (and there is a free version). Many others will do solid modelling and raytracing. I like Truespace, we use "3ds Max" at work.