Biomes contain all per-biome settings such as objects, terrain blocks, the terrain generator, and much more. You find & create biomes in the 'biomes' folder.


    "name": "Name",
    "derivative": "PLAINS",
    "vanillaDerivative": "THE_VOID",
    "layers": [{
        "palette": [{"block": "minecraft:grass_block"}],
        "maxHeight": 4,
        "minHeight": 3
    "generators": [{
        "generator": "plain",
        "min": 0,
        "max": 5

Biomes require quite some settings by default.

name is the name of the biome when it is ever displayed. This does not have to equal the name of the file, but it is recommended to be at least similar so you can find biomes back more easily.

derivative is the vanilla biome that is the underlying biome. Unless you specify customDerivatives, this will be the name as displayed in your f3 menu.

vanillaDerivative is the vanilla biome that dictates the color of the biome in a biome mapping such as /iris studio map.

layers contain the data for your terrain's topmost blocks. Layers consist of a palette, which contains the details of the blocks that are placed, and the minHeight & maxHeight, which dictate the minimal and maximal number of times this block is placed on the terrain.

generators are the Generators for this biome. These dictate the height of the base terrain (before placing the layers). The generator defines which generator is used, and the min & max values decide how low/high the generator can generate. min& max can be negative numbers, which results in water being placed (when the generator generates below 0), which is how oceans & rivers are made.

5 Elements

Five other settings that you will likely need when setting up a biome are:

    "children": [],
    "customDerivitives": [],
    "decorators": [],
    "slab": {},
    "wall": {},
    "objects": [],
    "effects": []


children are sub-biomes. This allows you to stack biomes inside biomes to make small spots of different trees, or lines of different terrain blocks, etc. Note that this is not intended to make lakes & rivers, use fluidBodies for that. You can modify how children spawn with childShrinkFactor and childStyle.

Custom Derivitives

customDerivitives are what allows Iris to create custom colors for your biomes. They also allow you to set many other values such as the color of the water, or a fake ID for the biome name (which is what shows up in the f3 screen).

Adding this means you have to reboot your server first, before being able to use the pack. FAQ


decorators are what allows you to place decorations in your biomes. You mainly need palette and chance, but it has multiple other useful settings, make sure to use VSCode's autocomplete for this one.

Slab & Wall

slab & wall allow you to place slabs and cliff-like walls on your terrain. Slabs can make your terrain look more natural / smooth. Note that walls are not intended to make ravines, see Caves & Ravines for more details on that.


objects decide which Objects are placed in this biome. This setting is also available in Regions.

The settings for object placements are likely to change soon, so we will not detail them here or in Objects. Use autocompletions!


effects allow you to make custom sound, particle and potion effects in a biome. Each of these options has its own respective setting, also placed within effects. Make sure to use autocompletions & descriptions.

Last updated