Because we’re often trying to simulate small wet transparent things we rely pretty heavily on stochastic raytracing. We can handle transparency, large light sources, depth of field, light scattering, etc. all at the same time. It’s a general purpose setup that works well for a broad range of “soft” phenomenon. Brazil is pretty fast, but there are limits to our patience, especially since the sampling isn’t reusable. Once you make any change at all to the scene, you essentially have to start over. So we try to get a lot of revisions done to refine a look and still keep the speeds good so we can get those revisions turned around quickly.

When you reduce the number of samples, you get a large increase in speed, but the downside is aliasing, which generally looks like noise, since it is stochastic.

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