World generation

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Basics Menus Game Creation Gameplay Pawns Plants Resources Gear Mods
Basics Menus Game Creation Gameplay Pawns Plants Resources Gear Mods
Game Creation Scenario system AI Storytellers World Generation Biomes

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Worlds in RimWorld are generated from either random or user-provided seeds that allow for a completely new experience every time. Each world is uniquely filled with multiple biomes that change what the world looks like and how it behaves. For example, some biomes feature a large amount of mountains, while others are full of grasslands.

Create world

The world generation screen appears during the creation of a new colony.

Reset Restores the map size to 200 x 150 and sets a new seed.

Seed A random seed is provided, but you may enter your own. A given seed always produces the same map layout.

Randomize seed Randomly picks a new seed.

Size The map size determines the (horizontal x vertical) number of map tiles.A larger map size offers a more granular selection of map tiles. For example, an island may appear as one square in a small map size but at a greater size it will consist of multiple selectable squares. The world map size has no effect on the in-game map.

Optional maps sizes:

  • 150x112
  • 200x150
  • 250x188
  • 300x225
  • 350x262
  • 400x300

Generate Click to continue with the current settings.

Once the player clicks Generate, the 'Select landing site' screen appears and shows the world map. Every square on a world is unique, with its own biome, elevation, average temperature, terrain, and rainfall amount. These details are shown whenever the player selects a square. In world generation four main features, biome, elevation, temperature, and rainfall, are generated with each tile. Clicking the Mode button (default is 'Full') offers the choice to select a feature to view the map in a special heat map. Each feature is logical with the tiles near to them. Each feature goes along with the biome of the tiles and the tiles around it. Each biome has its unique trees, animals, temperatures, rainfall and growing periods.

The player can click 'Select random site' or select one of the squares in which to land and build a colony.

Keyboard/mouse controls:
Mouse Controls
Left mouse button Select location
Right mouse button Clear selection
Mouse wheel Zoom in/out
Mouse wheel (click+hold) Pan
Keyboard Controls
PageUp Zoom out
PageDown Zoom in
Arrow up or W Pan up
Arrow down or S Pan down
Arrow left or A Pan Left
Arrow right or D Pan Right


There are six main features that affect game play in that tile on a generated world. These details are listed on-screen for the selected map tile.


Each map tile has one of the following terrain types: Flat, Small Hills, Large Hills, and Mountains. The terrain type determines the amount of mountain will be generated on the in-game map.


Each map tile has a certain amount of rainfall, given in average number of millimeters per year. It determines how often it will rain, not counting the automatic rain after a certain number of fire tiles are on the map.


A map tile's distance above sea level is its elevation. Higher elevation brings with it colder weather.


The coordinates of a map tile includes its latitude which affects its temperature range and amount of daylight (unconfirmed).


Each tile has its own averages for temperature based on the biome. Only the averages are presented in the world generation menu, but can directly affect your game. The effects of temperature vary greatly; extreme heat causes your colonists to develop heat stroke, while extreme cold may freeze them so thoroughly, their corpses will never decay. Temperature is related to the other three features of a tile in a generated world. Naturally, higher elevation and a more northern biome is colder.


There are nine biomes in Rimworld and—on a normally generated world—all of them are represented. They each correspond to specific features. Each biome is more likely to include certain features based on it's real world equivalent.

Basics Menus Game Creation Gameplay Pawns Plants Resources Gear Mods
Game Creation Scenario system AI Storytellers World Generation Biomes


<onlyinclude> During the world generation process, a world is created using a seed. A seed is a number or string used to initialize an algorithm. Each world is randomly generated using this algorithm and will consist of several different biomes. The world will generate an amount of the different biomes listed below with different terrain properties, including things such as height of terrain and rainfall. Once the world map is generated and displayed, the player can choose which of 8 playable biomes (9 in Alpha 16) they want to land in; each offering their own sets of flora and fauna, and their own unique sets of challenges.

The game splits the biomes into 3 categories: Moderate, Arid, and Cold. Here are the categories and biomes listed below, in order of intensity: A15 World Map

The following diagram is a simple chart of biomes by intensity, and therefore you could view this to see which biome could best suit your experience or playstyle: Biome Intensity Diagram

Moderate Biomes

These biomes are rich in flora and fauna, and also have a slightly elevated rate of disease. They generally have year-round growing periods, or longer growing periods at the very least.


A vast body of water, inhabited by all sorts of marine life and plants. As there are no solid places on which you can land: oceans are actually unplayable biomes.

Season, Temperature and Plant Growth Cycle

  • Season: Varies significantly: anywhere from year-round to never
  • Temperature: Annual average of around 30 °C (86 °F) in the south, down to around -30 °C (-22 °F) in the extreme north. Steady decrease the further north you go.
  • Plant Growth Cycle: Marine plants thrive in their own ways underwater - but this we shall never know for definite.

Temperate forest

A friendly biome dominated by forests of deciduous trees interspersed with fertile clearings. Many species of animals move around in the trees and on the plains.

Season, Temperature and Plant Growth Cycle

  • Season: Varies considerably, can be year-round or just 11th of Spring - 1st of Fall.
  • Temperature: An annual average of just above 0 °C (32 °F) is possible, up to an average of 20 °C (68 °F) in warmer climates.
  • Plant Growth Cycle: Depending on location, plant growth may slow during autumn and stop during winter.

Temperate Forest Small Hills

Tropical rainforest

A thick, moist jungle. Dense overgrowth and aggressive wildlife make construction and survival difficult. Tropical Rainforests are also notorious for sweltering summers and diabolical diseases, and even has the threat of Sleeping Sickness: a slow-progressing, long-lasting disease that is exclusive to the Jungles.

Season, Temperature and Plant Growth Cycle

  • Season: Year-round.
  • Temperature: Averages 20 °C (68 °F) to 30 °C (86 °F) over the course of the whole year. Heat waves generally push temperatures up to the 50 °C (122 °F) - 60 °C (140 °F) range.
  • Plant Growth Cycle: Plants thrive throughout the year. Heat waves can slow plant growth though.

Tropical Rainforest Large Hills

Arid Biomes

These biomes become progressively dry as they become more arid. Moderate amount of flora and fauna, which drops off as you pick a more extreme biome. Almost always a year-round growing period

Arid shrubland

A dry region, but not dry enough to become a true desert. Open plains with grasses and bushes give way to scattered groves of trees. Plants are hardy and there is a moderate density of animals.

Season, Temperature and Plant Growth Cycle

  • Season: Year-round.
  • Temperature: Ranges from an annual average of 20 °C (68 °F) to over 30 °C (86 °F). Heat waves during summer can push temperatures fairly above 60 °C (140 °F)
  • Plant Growth Cycle: The hardy plants of this biome grow well throughout the year.

Arid Shrubland Small Hills


A very dry area which supports little life. There are scattered areas of dirt which crops can be grown on.

Season, Temperature and Plant Growth Cycle

  • Season: Varies considerably. Can be year-round, or 1st of Summer to 11th of Summer.
  • Temperature: An annual average of over 20 °C (68 °F) is possible. In colder climates this can plummet to an annual average just above 0 °C (32 °F).
  • Plant Growth Cycle: Growth can slow during autumn and winter.

Desert Mountainous

Extreme desert

An extremely hot and dry area which is hostile to most life. Sufficiently fertile land is extremely scarce, much like in Ice Sheets. However, you may still get the occasional saguaro cactus and agave plant blow in, and it's warm enough for outside plant growth. There is sufficient gravel for good old potato farming, as rice isn't so hot on its heels on less fertile land.

Season, Temperature and Plant Growth Cycle

  • Season: From year-round to 11th of Winter - 1st of Winter.
  • Temperature: Annual averages generally from 20 °C (68 °F) to 30 °C (86 °F).
  • Plant Growth Cycle: Not quite as tight as ice sheets, but very few crops can be grown on the various areas of gravel around hills and mountains.

Extreme Desert Flat

Cold Biomes

These biomes become progressively colder and hostile as they become more intense. Flora and fauna becomes more scarce as you pick a more extreme biome. Disease rate is also lower in more extreme biomes, being almost non-existent on Ice Sheet.

Boreal forest

Northern forests of coniferous trees. Despite the harsh winters, boreal forests sustain a diverse population of small and large animals, and somewhat dense flora. You can find many raspberry bushes scattered around, and also a few large bogs which are 'fun' to traverse.

Season, Temperature and Plant Growth Cycle

  • Season: Anywhere from 6th of Spring - 6th of Fall or occasionally Never when bordering Tundras. Generally 11th of Spring - 1st of Fall or 1st of Summer - 11th of Summer.
  • Temperature: from 20 °C (68 °F) to 10 °C (50 °F) in summer, from -10 °C (14 °F) to -30 °C (-22 °F) in winter
  • Plant Growth Cycle: Reasonably hospitable for flora during the late spring months to early fall months.

Boreal Forest Flat


These mostly-frozen plains bear almost no trees and little vegetation. There are a few small animals interspersed with large herds of migratory grazers and their predators. Growing periods are generally very short or non-existent. This makes Tundra a challenging biome to survive on.

Season, Temperature and Plant Growth Cycle

  • Season: usually 1st of Summer - 11th of Summer or Never.
  • Temperature: Taken as an average through the year, can be as mild as 0 °C (32 °F) or as severe as -20 °C (-4 °F).
  • Plant Growth Cycle: Plants flourish briefly in the summer months.

Tundra Small Hills

Ice sheet

The surface is covered with sheets of ice which can be kilometers thick. There is no access to soil or rock, so there are no plants. The only animals seen here are migrating to somewhere else - or badly lost. Surviving is very difficult and dependent on unreliable hydroponic farming, and utilisation of gravel patches around rocky outcrops. Geothermal vents and potatoes are your best friends here, and should trust them with your life - not that there's much of a choice. Still, the inhospitable environment works both ways: Human enemies rarely show up due to the cold, and parasitic diseases are very rare.

Season, Temperature and Plant Growth Cycle

  • Season: Never
  • Temperature: from 1 °C (33.8 °F) to -40 °C (-40 °F) in summer, from -40 °C (-40 °F) to -120 °C (-184 °F) in winter
  • Plant Growth Cycle: In very mild ice sheets, some plants can be grown on areas of gravel during summer where temperatures can peak into low-mid double figures during the day.

Ice Sheet Large Hills

Sea Ice

This is where the sea has frozen over to the point where a thick ice sheet is formed, theoretically making it habitable. For those that thought Ice Sheet wasn't difficult enough: no flora, fauna or rocks - everything must be done via trading, or cannibalism, until you can eventually get hydroponics. Only for the true Bear Grylls' of the RimWorlders.

Season, Temperature and Plant Growth Cycle

  • Season: Never
  • Temperature: Unknown - presumably sub-zero at all times except mid-day in the peak of summer.
  • Plant Growth Cycle: Non-existent: there is no fertile soil - you can only grow using hydroponics.

Wild Inhabitants


Biome Agave Birch Tree Bush Cecropia Tree Dandelions Grass Moss Oak Tree Pincushion Cactus Pine Tree Poplar Tree Raspberry Bush Saguaro Cactus Tall Grass
Arid Shrubland
Boreal Forest
Temperate Forest
Tropical Rainforest


Biome Alpaca Arctic fox Arctic wolf Boar Boomalope Boomrat Capybara Caribou Cassowary Chicken Chinchilla Cobra Cougar Cow Deer Dromedary Elephant
Arid Shrubland
Boreal Forest
Extreme Desert
Ice Sheet
Temperate Forest
Tropical Rainforest
Biome Elk Emu Fennec fox Gazelle Grizzly bear Hare Husky Ibex Iguana Labrador retriever Lynx Megascarab Megasloth Monkey Muffalo Ostrich
Arid Shrubland
Boreal Forest
Extreme Desert
Ice Sheet
Temperate Forest
Tropical Rainforest
Biome Panther Pig Polar bear Raccoon Rat Red fox Rhinoceros Snowhare Squirrel Thrumbo Timber wolf Tortoise Turkey Warg Yorkshire terrier
Arid Shrubland
Boreal Forest
Extreme Desert
Ice Sheet
Temperate Forest
Tropical Rainforest