I'll catch up here in just a bit to discuss this further, but my updated grid based Line of Sight can do pretty much exactly that right now. Problem is the whole concept conflicts with the Shadow-Casting system I created in this recent demo. That's why it might be good to give the option to play either way. You might note that the mini-map now correctly updates only as you explore areas, and that areas you have already been remain viewable on it. That will be true no matter which way I end up doing the sight lines and shading.