Hi Drew!
I have download this tutorial and tried this effect in my [test level], I have used different models. now
I have seen that the models that locate near to the center, (where the two green lines in WED are crossed) then the model comes illuminated or if the model locates on the Y+ line or Y- then comes illuminated only from the side that has turned toward the center, while the part of behind is completely black! if I move the model on the X line or I remove it from the center then is seen all black!

from what does it depend? I have an ATI Radeon 9000 graphiccard 64 MB
However very nice work!
Greet
Salva