Benchmark scenes?

[Kresimir Tkalcec]

With very simple scenes, you won't get much speedup with more cores as not all parts of the code and 100% multithreaded so there are areas where cores have to sychronise and wait for the slowest one to complete.
However, with more and more voxels the speed gain will be more noticeable.
There is also a memory bandwidth bottleneck where all cores have to read/write from the memory and there isn't many math operations between those read/writes.