Biomes

What a mod can do with biomes, by what it wants. Each row names the call or file; the pages it links to give the detail.

Add a biome
Use
data/<ns>/worldgen/biome/<name>.json in a content mod or data pack (content mods)
Side
Content
Add my features or spawns to vanilla's biomes
Use
A biome modifier file in data/<ns>/neoforge/biome_modifier/ (content mods)
Side
Content
Give my dimension its own biomes
Use
DimensionSettings::biome_source: Fixed, Checkerboard, MultiNoise by preset, End, or Points for an explicit climate-point layout (dimension shape)
Side
Both
Know the biome at a position
Use
LevelRef::biome_at on a server level, LevelRef::client_biome on a client
Side
Server, client
Find the nearest biome or tag
Use
LevelRef::find_closest_biome with a BiomeSearch
Side
Server
Change a biome
Use
LevelRef::set_biome, one 4x4x4 cell, as /fillbiome does
Side
Server
Run bone meal at a position
Use
LevelRef::bone_meal
Side
Server
Tint foliage, grass or water by biome
Use
The register_color_resolvers hook for new colour resolvers, and the biome_colors hook to change a biome's own colours
Side
Client

Carver, climate and effects modifier support is implemented; that does not imply full custom serializers or phase ordering.

What is not here yet

Placing a mod's own biomes among the Overworld's or the Nether's: a design note, not code (arismoko/horizon#2554).
Full custom biome-modifier serializers and explicit phases between modifiers (#2732).
A mod's own worldgen registry loaded into the world (#811), and per-biome client effects (#2734).
Features and placers defined in code (#815).

Some of these have a PR open; a page for each lands with it.

biome_at never loads or generates a chunk: an unloaded column answers None.
find_closest_biome follows vanilla's sampled spiral, so it is not a search through cells a mod edited, and it refuses a search whose sample count passes BiomeSearch::MAX_SAMPLES.
set_biome refuses a client, an unknown biome and an unchanged cell, and returns false rather than an error.

Biomes

What a mod can do with biomes, by what it wants. Each row names the call or file; the pages it links to give the detail.

Add a biome
Use
data/<ns>/worldgen/biome/<name>.json in a content mod or data pack (content mods)
Side
Content
Add my features or spawns to vanilla's biomes
Use
A biome modifier file in data/<ns>/neoforge/biome_modifier/ (content mods)
Side
Content
Give my dimension its own biomes
Use
DimensionSettings::biome_source: Fixed, Checkerboard, MultiNoise by preset, End, or Points for an explicit climate-point layout (dimension shape)
Side
Both
Know the biome at a position
Use
LevelRef::biome_at on a server level, LevelRef::client_biome on a client
Side
Server, client
Find the nearest biome or tag
Use
LevelRef::find_closest_biome with a BiomeSearch
Side
Server
Change a biome
Use
LevelRef::set_biome, one 4x4x4 cell, as /fillbiome does
Side
Server
Run bone meal at a position
Use
LevelRef::bone_meal
Side
Server
Tint foliage, grass or water by biome
Use
The register_color_resolvers hook for new colour resolvers, and the biome_colors hook to change a biome's own colours
Side
Client

Carver, climate and effects modifier support is implemented; that does not imply full custom serializers or phase ordering.

Placing a mod's own biomes among the Overworld's or the Nether's: a design note, not code (arismoko/horizon#2554).
Full custom biome-modifier serializers and explicit phases between modifiers (#2732).
A mod's own worldgen registry loaded into the world (#811), and per-biome client effects (#2734).
Features and placers defined in code (#815).

Some of these have a PR open; a page for each lands with it.

biome_at never loads or generates a chunk: an unloaded column answers None.
find_closest_biome follows vanilla's sampled spiral, so it is not a search through cells a mod edited, and it refuses a search whose sample count passes BiomeSearch::MAX_SAMPLES.
set_biome refuses a client, an unknown biome and an unchanged cell, and returns false rather than an error.