Being confused about the example of Combining Stratified Sampling and Importance Sampling in Advanced Global Illumination (P72,P73).

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I know how to do importance sampling and stratified sampling. But I can't understand this example and the code.

Is this example to calculate $S$ stochastically or to get a random number $u$?

What is the $u$ for?

What's the meaning of "Sample the $i$th term of the sum $N_i$ times"?

  • 1
    $\begingroup$ Can you clarify your question? Just saying "I'm confused" doesn't give us much to go on. What do you understand already, what don't you understand, what specific questions do you have? $\endgroup$ Aug 8, 2017 at 22:22
  • $\begingroup$ I don't understand what the question is. $\endgroup$ Aug 9, 2017 at 1:11
  • $\begingroup$ @NathanReed Question updated. $\endgroup$
    – chaosink
    Aug 9, 2017 at 13:46
  • 1
    $\begingroup$ @JulienGuertault Question updated. $\endgroup$
    – chaosink
    Aug 9, 2017 at 13:48


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