Goods spread functions

A good distribution is an expression that decides whether the good can be placed in a cell. Fantasy Map Generator allows you to write custom distributions, but it requires some understanding of how they work. Goods are generated before states and cultures, so distributions can only rely on geographical data. Once a distribution is changed, the good placement has to be regenerated — the Goods Editor does that for the edited good.

How placement works

Cells are processed in random order. For every cell the generator walks the (reshuffled) list of goods and takes the first good that passes all of these checks:

1. the good has both a distribution and a non-zero chance;
2. the good has not yet reached its cell cap of ceil(200 × cells count / 5000) cells;
3. a random roll against the good chance (in percent) succeeds;
4. the distribution expression evaluates to true.

A cell holds at most one good. Glacier cells are skipped entirely while the Glacier biome habitability is 0. Because goods are reshuffled as the generator walks the map, no good gets a systematic advantage over the others.

Technical info

Technically a distribution is an expression evaluated for each cell to return true or false. If true is returned, the good can be placed in the cell. The expression is plain JS, so you can use logical operators (! for NOT, || for OR, && for AND) and parentheses.

The expression can only call the built-in functions below. They make the syntax easier to read and write:

• random(number): percentage of true, e.g. 50 will return true in 50% of cases
• nth(number): true only for every n-th cell (cells whose id is divisible by the number). For example nth(2) skips 1/2 (50%) of cells and nth(5) skips 4/5 (80%) of cells. Unlike random(), this is deterministic for a given cell
• minHabitability(number): true if biome habitability is at least the supplied value
• habitability(): check against biome habitability. Always true for habitability >=100, false for 0, skips 50% of cells if habitability is 50 and so on
• elevation(): random check against the cell height — the higher the cell, the greater the chance. To make a good more frequent in low areas, negate it: !elevation(). The function takes no arguments; anything passed to it is ignored
• biome(biomeId, biomeId, ...): check against list of biome ids, see below to get biome id reference
• minHeight(number): true if cell height >= number. Number is in range [0-100], where 0 is deep ocean and 20 is minimal land elevation
• maxHeight(number): true if cell height <= number
• minTemp(number): true if cell temperature (in Celsius) >= number
• maxTemp(number): true if cell temperature <= number
• shore(ringId, ringId, ...): check against distance to the closest shoreline. 1 is land cells next to water (coastline), 2 - next land ring, -1 - water cells next to land (shallow water), -2, -3, ... - deeper water cells
• type(string, string, ...): check against the feature subtype (or feature type). Types of all water cells connected to map border is ocean, lake types are freshwater, salt, sinkhole, frozen, lava and dry. Land subtypes are continent, island, isle and lake_island
• river(): true if there is a river in the cell

Biomes ids

• 0: Marine;
• 1: Hot desert;
• 2: Cold desert;
• 3: Savanna;
• 4: Grassland;
• 5: Tropical seasonal forest;
• 6: Temperate deciduous forest;
• 7: Tropical rainforest;
• 8: Temperate rainforest;
• 9: Taiga;
• 10: Tundra;
• 11: Glacier;
• 12: Wetland.

These are the default biomes. Biomes can be edited in the Biomes Editor, so to get the actual ids of your map run pack.biomes.map(b => b.i + ". " + b.name) in the browser console (F12).

Examples

Let's say we want a good to be generated in hot and highly elevated areas. If the altitude is medium, let it also be allowed, but rarely. The expression will be something like minTemp(15) && (minHeight(70) || (minHeight(40) && nth(5))).

Another common case is a good whose frequency varies by biome. Combine biome() with nth() or random(): biome(1) || (biome(2) && nth(2)) || (biome(3) && nth(3)).

Default catalogue

The distributions used by the built-in goods, as a starting point for your own:

Good	Distribution
Wood	biome(5, 6, 7, 8, 9)
Stone	`(minHeight(40)
Marble	`minHeight(60)
Iron	`minHeight(60)
Copper	`minHeight(60)
Tin	`minHeight(60)
Silver	`minHeight(60)
Gold	river() && minHeight(40)
Grain	minHabitability(20) && habitability()
Cattle	`(biome(3, 4) && !elevation())
Fish	`shore(-1) && (type("ocean", "freshwater", "salt")
Game	biome(5, 6, 7, 8, 9)
Wine	`biome(6)
Olives	biome(3) && shore(1, 2)
Honey	biome(6, 8, 9)
Salt	`shore(1) && type("salt", "dry")
Dates	biome(1)
Horses	`biome(3)
Elephants	biome(1, 3, 5, 7)
Camels	biome(1, 2)
Hemp	biome(6, 7, 8)
Pearls	shore(-1) && minTemp(18)
Gemstones	`minHeight(60)
Dyes	`shore(-1)
Incense	biome(1, 7)
Silk	biome(7)
Spices	biome(7)
Amber	shore(1) && biome(6, 7, 8, 9)
Furs	`biome(9)
Sheep	`(biome(3, 4) && !elevation())
Slaves	shore(1) && minHabitability(1) && !habitability()
Tar	`biome(1, 2)
Coal	`minHeight(40)
Oil	`biome(1, 2, 10)
Mahogany	biome(5, 7) && random(50)
Whales	shore(-1) && type("ocean") && maxTemp(7)
Sugarcane	biome(7)
Tea	`minHeight(40) && (biome(5)
Tobacco	`random(20) && (biome(3)
Clay	`minTemp(8) && (shore(1)
White sand	`minTemp(8) && (shore(1)