|Regardless of light direction, the blue path is followed. Regardless of light direction, the larger of the two angles (pictured as theta) is used for the Schlick approximation.|
A sharp reader of my mini-book pointed out I have a bug related to this in my code. I was surprised at this because the picture looked right (sarcasm). The bug in my code and my initial fix is shown below.
|The old code shown in blue is replaced with the next two lines.|
|Old picture before bug fix.|
|New picture after bug fix.|
I am reminded of spherical harmonic approximation to diffuse lighting. It looks different than the "correct" lighting, but not worse. (In fact I think it looks better). What matters about hacks is their robustness. It's best to do them on purpose though...