Light Textures...

I've scanned the memories, but maybe I'm just missing it. I'd ask the wonderful Miss teh_indy how to do it, but she has a policy against asking how to get such-and-such effect. Anyway. How would one make a light texture? Not how to use it, but how to make one? From scratch, on your own. I've seen how to use an image [blur it, screen it, yeah], but that's not what I want.

I'm sorry to be a pest. The answer is probably blatantly obvious, but humour me on this one, ok?


Thank you!