The idea is that there is always a relatively low number of entities in the high simulation set - like, less than 500, less than 1000, something like this. Those are always processed. Then, however many low entities there are (a million, ten million, we don't care), we will simply process n of them a frame where n is however many we can afford to process. Say that is 10000. Then each frame we process 10000 low entities, which means each low entity gets updated once every n/1000 frames, which for 1000000 low entities would be once every 1000 frames, about once every 30 seconds.
Ideally we will be able to "process" a rather large number of low entities per frame, because a lot of them will not have anything to do (they are things like trees, which just sit there most of the time).
- Casey