13.8 Careful sample placement
A classic and effective family of techniques for variance reduction is based on the careful placement of samples in order to better capture the features of the integrand (or, more accurately, to be less likely to miss important features). These techniques are used extensively in pbrt. Indeed, one of the tasks of Samplers in Chapter 7 was to generate welldistributed samples for use by the integrators for just this reason, although at the time we offered only an intuitive sense of why this was worthwhile. Here we will justify that extra work in the context of Monte Carlo integration.
13.8.1 Stratified sampling
Stratified sampling was first introduced in Section 7.3, and we now have the tools to motivate its use. Stratified ...