Lecture 13: Global Illumination & Path Tracing (36)

Based on this slide and the previous slide, is transport the opposite of reflection?


They're not the opposites per se, they're like two steps in a "bounce." It's important that there's two different surfaces, and that light bounces off one first, and then to the other.

Reflection: takes incoming light on the first surface and gives you the outgoing light on the first surface. So reflects off the first surface.

Transport: takes outgoing light on the first surface and gives you the incoming light on the second surface (the result of the first outgoing light). So it "transports" the outgoing light of the first surface to the incoming light of the second surface.

After both of these steps, you get a "bounce": you start with light entering the first surface, and you end with light entering the second surface, like a full step ahead. This is what the KK operator means a few slides down.


I was confused by this slide at first because it seems like transport is related to reflection (especially with the -w_0 term; seems like some sort of angle reflection/bouncing), but now I see that transport literally refers to the process of "transporting" light from one surface to another surface, and the negative is there just because an "incoming" direction for one surface is the negative, "outcoming" direction for the other surface.

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