Neat! Parallelizing a single frame across multiple machines was something I'd wanted to try back when I was working on RenderMan. It used to be able to do it back in the REYES days via netrender, but was something we lost with the move to pathtracing on the RIS architecture.

Could you go into a bit more detail on how the work is distributed? Is it per tile (or some other screen-space division like macro-tiles or scan-lines)? Per sample pass? (Surely it's not scene distribution like the old Kilauea renderer from Square!) Dynamic or static scheduling? Sorry, so many questions. :-)