It is random for the most part - wherever nothing else is specifically designed, that is.
Scenery is dynamically generated by a complicated arrangement of noise functions and filters assembled into the "Map Magic 2" terrain plugin for Unity. It can generate an infinite world on its own if you let it, but making it look authentic and pleasant to behold still takes a lot of fiddling around.
Despite what the name implies, it isn't
really magic... It's a very powerful tool, no doubts that, but like all such things, it's equally good at making sceneries that are totally awesome or egregiously repellent - You can hook it up any way you like.
My setup here for now has only one
Biome, which is good enough for plains and rolling hills with some casual heights here and there - It follows a continental-scale map which determines just how vertically intense any given area may get as you fly through it. (at zero, you get the ocean) - Eventually there will be other biomes, for making deserts, jungles, glaciers, etc, and then we'll map these to different parts of the world in a similar way.
This allows us to have a "
Known World*" mapped out, so we can have a number of common destinations charted up before you start exploring "here be dragons" country.
* map is a work in progress -- The starting airfield location is "Haven Rock"This area comprises a real estate of just about exactly one million km²...
At those scales, the terrain system has to be capable enough to do it's own thing and populate that huge land with stuff like towns and villages and whatnot - Most of the smaller towns and settlements will be thus dynamically generated.
Yet I'm making a point of working it out such that major locations and terrain features can still be inserted "by hand" at arbitrary coordinates so that they get included in the whole process. The end result should be that one cannot easily tell what bits of the world were made by man or machine.
This is pretty similar to how FSX handles scenery layers, though Unity allows us working in a far more visual, hands-on way for it
Anyhow, it's not totally random, that is: Two different players will always find the same randomly generated features at a same given location. This is called "pseudo-random", and it takes a "seed number" to roll the logical dice and create random results unique to any given number. Naturally, the seed number for our world is
42And of course, as you get closer to the "edge of the world", the known-world continental map gradually transitions away, smoothly giving full authority to a fully procedural system which then goes on to infinity. And there'll be support for mods, so that custom terrain features can be added wherever you like... but that's still quite a bit ahead for now
Anyways, that much is still quite some way ahead of me on the almighty to-do list - There are more basic things to sort out before we come back around to the terrain engine (but soon, we shall)