@shamanix Comparing it to Schlick on dielectrics I didn’t find the delta relevant. But on conductors, unless the dip around the 80 degrees is prominent it doesn’t do a great job at them, and for commonly authored metals it doesn’t do as well as Schlick. It doesn’t do much better on chromium which is a material Schlick is known to not reproduce well, it does better on aluminum (probably why it was shown), but on other conductors it isn’t much better and can be worse like on gold or silver.

@pzurita @shamanix Hi, I'm the author. The fact that the approximation only depends on f0 and not a complex valued IOR (which also shapes the curve in different ways for equal f0s) makes it impossible to get a better match on chromium and will also mean it will be worse on other metals. At least for the example metal selection I randomly chose it has a lower error on average. For dielectrics it's indeed essentially the same approximation.