Stuart:

Stuart:
> Something has changed in the environment manager which means that clouds
> generateion is now inconsistent. I'm still tracking it down, as my recent
> changes shouldn't have affected this.

Well, the cause was a bug in my code, but it didn't expose itself until we moved
to multiple cameras. The attached patch fixes the problem.

I've also put in a new heuristic to improve the frame-rate. Clouds that are already sorted
are likely to still be sorted in subsequent frames. Therefore I've put in a back-off
mechanism for the bubble-sort pass. This should mean that if you stay completely
stationary, once the clouds become sorted they will eventually only perform a
bubble sort pass every 128 frames.