Here's a question - would it be possible to implement an object or command that would gradually load the current planet terrain, radiating outwards from the player. It might be a useful way of trading off idle time for gameplay smoothness.
A mid-to-high end desktop circa three years ago. I have experienced a fair amount of lag and waiting-to-generate invisible walls when moving quickly, for example in vehicles, hence the suggestion to optionally pre-generate terrain.
Wouldn't that defeat the purpose of vehicles? Or is it the idea to keep a very large area loaded for a long time while you are playing?
Well, the purpose of vehicles is to move you around at a fairly decent speed. Also, the area doesn't need to be kept in memory at all times, just generated and saved the the planet's data file so it can be simply retrieved, rather than need to be generated on the fly.