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Biomes

A biome is a ground type: the grass, dirt, road, rock, sand or gravel painted across a map with the Biomes tool of the Map Editor. The game has 24 of them, numbered 0 to 23. A mod can repaint any of them with a new texture, and the change shows on every map, shipped or custom.

A biome mod changes the look only. How fast people and aircraft move over the ground, which runway tier it counts as, and similar rules live in the Biomes table and are changed with CSV tables.

Quick start

Give the first grass a new texture:

Mods/
  my_ground_mod/
    Biomes/
      8.png

Restart the game and load a save or start a map. Everywhere the map uses that grass, you now see your texture.

Restart after every change

Biome textures are imported once, when the game starts. After you add or change a PNG, or switch the mod on or off, quit the game completely and start it again. Loading a save, Refresh and the Enabled switch in the Mods window do not re-import them.

How it works

  • Biomes/ holds one PNG per ground type, named after its number: 8.png repaints ground type 8, the first grass (see the list).
  • The number is written in plain digits without leading zeros: 8.png, not 08.png. A number outside 0 to 23 is reported in the log together with the valid range.
  • Only files directly inside Biomes/ count. Subfolders, other file types and other names are reported in the log and ignored.
  • A mod cannot add new biomes, only repaint the 24 that exist. A map remembers which biome is painted where by number, so there is nothing a new one could be attached to.
  • The biome's surface detail and its burnt look after a fire are not replaced.
  • The game's own textures are untouched on disk. Switching the mod off (and restarting) brings the original ground back everywhere.
  • The repainted ground is put together on the graphics card. On a computer whose graphics card cannot copy textures there, biome PNGs are not applied and the log says so. There is nothing to fix in the mod then.

The texture

Rule Limit
Format A real PNG. A JPEG renamed to .png is refused.
Size At most 4096 × 4096 pixels (each side on its own)
File size At most 10 MB

A PNG over a limit is not scaled down: it is skipped with a warning in the log, and the game's own ground stays. Within the limits, the game resizes your texture to the size of its own ground textures, so any size works; a square image avoids stretching. The texture repeats across the ground, so it should tile seamlessly: the left edge must continue into the right edge, the top into the bottom.

Biome names

The number is the biome's row in the Biomes table. Rows with the same number describe how that ground plays.

Number File name Ground
0 0.png dirt
1 1.png dirt
2 2.png dirt
3 3.png dirt
4 4.png dirt
5 5.png dirt
6 6.png dirt, also laid under parking spots, gardening plots and dirt runways
7 7.png dirt
8 8.png grass
9 9.png grass
10 10.png grass
11 11.png grass
12 12.png grass
13 13.png road, also laid under tarmac runways
14 14.png road
15 15.png road, also laid under concrete runways
16 16.png rock
17 17.png rock
18 18.png rock
19 19.png sand
20 20.png sand, also laid under sand runways
21 21.png sand
22 22.png gravel, also laid under gravel runways
23 23.png grass

The runway surfaces are the built-in values of the AirstripTiers table (Biome Id column); a mod that changes that table changes which ground is laid.

Biomes and the Biomes table

The two are independent and combine freely:

You want to change... Use
What a ground type looks like Biomes/<number>.png (this page)
How a ground type plays: movement speed, runway tier, wear on stored goods, fire spread The Biomes table, row <number> (CSV tables)
Which ground is painted where on a map The Biomes tool in the Map Editor

Several mods, same biome

If two enabled mods repaint the same biome, the mod applied last wins, and the log notes which one overrode which. See How mods work for the order.

When something does not show up

  • Did you restart the game? Biome textures are only imported at game start.
  • Is the file directly inside Biomes/, named with a number from 0 to 23 and no leading zero?
  • Is it a real PNG, at most 4096 × 4096 pixels and 10 MB?

Problems are written to Player.log on lines that start with [Mod <your mod id>]. The detailed lines may only appear in development builds, so if the log is silent, go through the list above. The size limits for all art are also on Objects and models.