Sampling and Quality Control
Final Render (In Maya 2013)
The sequence of images below display the development towards Maya's immitation of 'final gather' Final gather is essentially bouncing light. The way light will hit, say, a white work surface and then bounce off and be reflected on nearby objects. Its is seen everywhere in the natural world, but it takes a few settings to recreate within Maya.
The three images above show the differences when adjusting the accuracy, point density and point interpolation. As can be seen it progressively mottles the render.