“Light makes right.”
In Chapter 9 we discussed the theory of physically based materials, and how to evaluate them with punctual light sources. With this content we can perform shading computations by simulating how lights interact with surfaces, in order to measure how much radiance is sent in a given direction to our virtual camera. This spectral radiance is the scene-referred pixel color that will be converted (Section 8.2) to the display-referred color a given pixel will have in the final image.
In reality, the interactions that we need to consider are never punctual. We have seen in Section 9.13.1 how, in order to correctly evaluate shading, we have to solve the integral of the surface BRDF ...