Deriving Lambertian BRDF from first principles

Started by JeGX, October 25, 2019, 01:06:00 PM

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This is a short exercise on integration. We will derive the Lambertian BRDF from first principles to understand the origin of PI in it.

We start by stating that the Lambertian BRDF is R/PI, where R (albedo) is the measure of diffuse reflection. It is the proportion of incident light that is reflected from a surface and is used to denote how bright a surface is (not to be confused with how reflective a surface is). Albedo maps are used ubiquitously in lighting, and look like this.