Lecture 13: Global Illumination & Path Tracing (81)
ekwkk

How are we choosing the probability prrp_{rr}? Are there any choices of prrp_{rr} that might make Russian Roulette unfavorable over just using N bounces?

rollororo

Is prrp_{rr} a fixed probability for all possible paths? By doing that, it would introduce some bias right?

HJQ2000

I think the point of probability prr here is to cut off the infinite recursion. It is not a fixed value, should be determined from efficiency consideration. My understanding is that prr is small if brdf for the next bounce direction is low, but not sure if there is a mathematical relationship between the two.

herojelly

How do we know this algorithm is guaranteed to terminate? Isn't it possible (though unlikely) our algorithm will keep rolling numbers under prrp_{rr} and thus never return 0 for XrrX_{rr}?

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