AdamB,
No, the calculation that I'm doing is in the reversed direction. I do not want to raytrace the whole model and see what I hit,
I want to select a face (or a few faces) and say how much of it is lit. (i.e. out of the set of rays that should hit it, how many actually hit it first)
This is working great, as already stated, for non-grouped/componented selections...