My attempt at mapping shader code to radiometric units:
Coutput
= Clight I Radiant Intensity I W/sr
/ pow(distance, 2) I * sr Radiant Power F W
* dot(N, L) F / area Irradiance E W/m²
* Calbedo E * BRDF Radiance L W/m²/sr
Radiance Coutput is PI times greater than it should be
we can ignore this for video games ...