it's raining outside now, i can hear it. i don't need to simulate every raindrop to give me a high fidelity impression that this is what is happening. i can even get my ass up and put on my coat and go outside, and i still wouldn't need to simulate everything. npcs are no different to us in this simulation, it is simply what is pressing wasdf that changes. the camera frustum, or more broadly the frustum of observation that either a player character or non-player character are the same. most of the time the npcs don't even need to be rendered, just some low level book-keeping logic for ones that are within an actual players realm of cognition. like i see the lady at the sandwich shop occasionally and expect her to remain relatively stable. i don't need to know if she exists once i leave the shop. for the most part an almost infinitesimal region of the open world simulation actually needs to be ticked at any particular moment. stuff that i see, or stuff that drives the plot.
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