If you go lower than 4, things can get pretty patchy. This can be good for debugging, though. Must be no more than 10, since that is the size of the array allocated. The default value is 6. This feature is not yet implemented.
Valid values are one and two.
The default value is 1. This will make everything maximally patchy, so you'll be able to see the borders between patches. There will have been a radiosity calculation at the center of most patches. As a bonus, this is quick to run. This will get better values, and more of them, then interpolate among more of them on the last pass.