Brightness decays quadratically, but I'm not so sure about luminance (which is supposedly what the author is referring to.) Edit: actually, luminance depends o

Brightness decays quadratically, but I'm not so sure about luminance (which is supposedly what the author is referring to.) Edit: actually, luminance depends only on angles. But since the perceived brightness of a reflected source is not a point-light source, I still don't know how it all ties together.