OptionalcameraCamera for level of detail.
OptionalcitySettings shared by every settlement (centre, size, radius and seed come from the population; sizes maps it onto cities).
OptionalframeFrame to lay settlements out in (world.frame by default).
OptionalmaxMost settlements to build, largest first.
OptionalpopulationWhere people live: the population model's settings (its center and radius are the area to populate).
OptionalsceneIf given, the group is added to it and updates itself via scene.onBeforeRender.
The world.
Input of Settlements.create: settings plus the objects it needs.