Originally Posted by
Lo Zeno
Regardless of the approach, I don't think they should choose the MAX value, and instead keep doing additive light, because light... IS additive, as pindercarl said. Two lamps make a room brighter than just one. In real life, you can even see the same effect as the pictures posted by kevininrussia, the only difference will be that the edges won't be as clear-cut because of the scattering caused by particles in the atmosphere, other diffused lights and lack of "perfect" darkness around.
I'd rather see some approximation of light diffusion, to make the gradient of the overlapping light "smoother", than not have additive light.