No multiple importance sampling. Notice how the surface plate is still somewhat noisy and there these annoying black specks.
With multiple importance sampling, the noise situation is much better. But the underside of the spheres is a little dark.
Irradiance caching, with an error threshold of 0.2. The lighting is better, but there are artifacts caused by the irradiance cache interpolation.
Irradiance caching, with an error threshold of 0.05. The artifacts are much reduced. I stopped here to avoid unnecessarily long render times.
