Surprisingly, IGN actually did a decent series of pre-release videos with a lot of direct interviews. There was one that covered, loosely, how creatures are generated. I'll try to dig it up, but the gist was this:
e:
Here we go.They start by having the artist design base forms for different creature types. Their algorithms extrapolate those into different species by changing all their physical features in different ways. Those extrapolations then undergo the same process to create
more species, diverging in different and more radical ways each cycle. So you're going to have batches of creatures which loosely resemble each other, but you're also going to have ones which are radically different.
IIRC the behaviors and such are not directly connected to the physical form (though really bizarre stuff tends to be more dangerous/aggressive), but instead to the environment in which the creature exists. There are also activity cycle variations--some creatures are nocturnal, some diurnal, some active throughout the day and night.
Also, from what I recall, both creatures and terrain are supposed to get more extreme the closer you get to the core. It's just a stab in the dark, but I suspect that they might have actually layered the creature divergences like that--the stuff most closely related to the base forms tend to be near the galactic rim, while the stuff that's undergone a lot of cycles of generation is close to the core.
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I've seen in video coverage a little wonky terrain where you have overhanging cliffs and arches that are nearly paper-thin at the edges, but nothing as bad as you normally see with extreme voxel terrain--it usually ended up looking like weird shale sheets. The main issues with terrain are the old voxel non-physics where you can carve out floating chunks, and with the clear chunk-area lines on the surface of large bodies of water. There also looks to be some weirdness with how ships land on really uneven terrain, but honestly that's preferable to having your ship tip over and break because it landed on a rock.