The terrain in Embark is generated using 2 levels. The first level is at the planet level. The planet is generated with the help of the Libnoise library. Then the map generated is modified by hand. Biomes, temperature, precipitation, and other macro level details are also captured.
The next level would be individual “tiles”, the planet is divided into 512 tiles. Each tile is large at 4km^2 of area. The terrain in the individual tiles use the info from the planet level as a base but add various bits of fine detail depending on the biome type. The player isn’t restricted within a tile but is able to travel between tiles, but be warned the tiles get progressively more hostile.
The initial alpha release of the game will focus on game play at ground level. There will be caves but they will be very basic. A complex cave system complete with underground rivers will be added before release.
In the first version of the game the simulation will only focus on a single tile at a time. But eventually the plan is to allow players to create networks of towns and fortresses which are simulated on the macro level. We feel that by mixing both hand painted terrain maps and procedural generation we can create terrain which has the best of both worlds.