I'm not sure Sean has ever spelled this out exactly. If memory serves, he used the phrase, "10% of the planets will be a utopia", as in, the grassy life-filled planets they've demoed. That's not to say that 90% will be uninhabitable rocks. I don't think they've been clear enough to say for sure.
Right, most planets will likely have at least some POIs. From crashed ships, to supply caches, to alien installations, or even just element-rich deposits ready to be mined. Those could end up being on even the most barren of rocks. I doubt we'll find many entirely barren planets, even if they're devoid of "natural" life.
What Hello's art team is doing is building only the base models. NMS' procedural code then takes those base forms and changes various elements to make the kinds of variants you see in that image. So, there could be base models that look like a deer, a badger, a t-rex, alien slug, etc., and from each of those an infinite amount of variants are generated. I assume something similar is done for the vegetation. Given that there will be hundreds of base forms, I'm not too worried about things getting repetitive.
I think the number of base forms is the biggest question when it comes to the diversity of the wildlife. It's hard to imagine this small team being able to crank out so many different base models, considering each one needs to be rigged and have basic animations applied to it (which obviously get tweaked by the algorithms). But I would love to be wrong about this and to keep discovering new weird and wonderful forms of life for hundreds of hours.
What is probably persistent locally:
* Planets, including all life on them. Another player would see the same mountain you did. They will not see that you blew a hole in it.
* Galactic map, which is probably generated from the same seed value
What is probably stored in the cloud:
* AI-controlled ships. Sean has said blowing up a space station will be persistent for everyone. I'd also think the economic system is probably centralized in the servers, though Sean says you can play offline so I'm not sure how that would work.
* Factional areas, if these are hand-picked by Hello. Otherwise they're probably generated procedurally like the map is
* Your discoveries
Other than maybe a few easter eggs, I doubt Hello games will be hand-picking the placement of anything in this universe. The Universe they've created is just too massive. To put it in perspective: If this game is wildly, wildly successful, and sells 10 million copies,
every single player could still have over 100 BILLION planets all to themselves. Now in reality the chances of finding other players discoveries (or other players) will go up dramatically as we approach the center, and 99.99999% of those planets will never be discovered, but that just represents the scale of the universe we're dealing with. Factions will absolutely be procedurally generated, though they will probably (hopefully) cover a wider swath of space than individual systems.
What is stored on the Atlas database is likely stuff that is easy (and quick) to store. Names, coordinates, and whether it exists or not is a very small amount of data to store about each discovery. Remember, when there isn't a player present at a location, nothing at that location "exists".
Think of it like a sea of math, and we're traveling through it in a bubble. As we travel through this sea, everything that enters the bubble springs up into existence, and then reverts back to raw, static math when we leave. It's highly likely the placement of spaceships and animals will be based on
when we arrive at that location. So if we arrive in a system at a certain time, that might be when a fleet is "scheduled" to warp in. But if we arrive an hour later, that fleet might be long gone. If we manage to destroy said fleet, then that fleet would stop existing for other players, and a competing local faction might occupy that system. It is potentially possible that they're doing some sort of limited simulation of conflicts between factions
once they are discovered, but it would probably be a pretty rudimentary simulation (who won/lost a particular battle/sector). One thing I'm particularly curious about, and I don't think anyone has asked Sean about: I wonder if it is even possible to hunt a certain faction to extinction? Makes me wonder how many different procedurally-generated factions will be in the game.
Things like economies can be simulated pretty easily on the fly based on what resources are available in the local region. It's possible they may have a more complex, active economic model driving things under the hood, but that remains to be seen.
The big question about saving local content will be "how", and "how much". Individual dead animals are easy to track, because again, just location, and status (plus the saved configuration of parts that make up that animal). However if we're to believe we can actually cause the extinction of a particular species, then the quantity and locations of animals on a particular planet would need to be created by the procedural algorithm and stored/tracked. Depending on how many animals are on each planet, that could be a lot of data to keep track of.
Storing terrain deformation information is an even bigger issue, because saves sizes can get out of hand quickly if you save
everything. It's possible they could be storing deformation data programmatically (ie recording explosion information to be redrawn later), which would be cheaper to store, but would have the potential problem of having to be "drawn in" when you get near it. If the deformation is extensive, it might create some nasty pop-in as the game has to recreate the huge network of craters you left on a location.
The questions about how this game works "under the hood" are the most interesting to me. Hopefully we get a few more answers before release.