Dynamic Light Occluded?

[Piranhi]

A quick question, if I was to have a dynamic light light up a whole level, for example, would meshes that were out of sight still use resources? Or would it only be what was available at the time?

I ask, because I'm trying to make a lightning type effect and I was going to use a toggleable directional light to simulate the lightning flash and shadows.

[sueds]

edit :

I didn't read your question properly. So you want to occluded shadow that arent in the screen. I think using modulate shadow will do the tric since shadow fade when you are away.