Indigo Renderer features a world-class implementation of Metropolis Light Transport (MLT), a sophisticated algorithm capable of meeting the exceptional demands of pure unbiased rendering.
Pushing the limits of unbiased rendering
MLT helps most in scenes with complex illumination, where unbiased rendering traditionally struggles to capture important illumination effects. Instead of spreading computational power evenly, MLT concentrates effort where it gives the greatest contribution to the final image. This powerful approach lets you apply the unparalleled accuracy of unbiased rendering to real-world scenes.
To illustrate the difference MLT can make we have rendered an underwater submarine (model courtesy of Anders Lejczak) using sub-surface scattering, which produces realistic shafts of light that illuminate the scene.
Both images rendered for 2 hours on an Intel Q6600 quadcore CPU; the above image was rendered with MLT enabled, the image below without MLT. The difference is striking, and it would take much longer without MLT to match the result obtained with MLT.
It's not rocket science (to use)
This sophisticated technology is available in Indigo Renderer as a single toggle-able option.