Generates the population of a region of a world: pure and deterministic (same world, options and
seed → identical result).
Habitability per fine cell from the world: dry land, not an avoided biome (glacier, peaks,
volcanic, deep ocean), gentle slope, comfortable temperature, fertile biome, fresh water or a coast nearby.
Central places (Christaller, with H3's aperture 7 as his K = 7 administrative principle): urban
centres are local maxima of smoothed, seeded-jittered habitability at the coarsest tier; towns,
villages and hamlets follow, one resolution finer each, in the market areas between them.
Rank-size: the r-th settlement (by tier, then score) gets P₁ / r^zipf people.
Settlement people spread over nearby cells with a Gaussian distance decay; rural people spread
over habitable land, denser along rivers and coasts and near settlements.
Generates the population of a region of a world: pure and deterministic (same world, options and seed → identical result).