dev.polymodloader.api.worldgen

Generated

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Type	Kind	Description
BiomeDefinition	record	A biome defined in code.
BiomeDefinition.Builder	class	Builds a BiomeDefinition.
BiomeSelector	interface	Chooses biomes: by ID, or by biome tag such as minecraft:is_overworld.
BiomeSelector.ById	record	—
BiomeSelector.ByTag	record	—
BiomeSpawn	record	A mob that spawns in a code-defined biome.
CodeFeature	functional interface	A placed feature written in code: a boulder, a plant patch, an ore cluster with a custom shape.
ColumnBuilder	interface	One block column being generated; valid only during TerrainGenerator.fillColumn.
FeatureContext	interface	Where and with what a CodeFeature places blocks, valid only during CodeFeature.place.
FeaturePlacement	record	Where a CodeFeature is tried in each chunk: how often, and at which height.
GenerationStepName	enum	The feature placement steps of world generation, in the order the game runs them.
NoiseFunction	functional interface	A density value per block position, used inside the game's noise terrain as a density function (WorldgenRegistrar.densityFunction).
StructureBuilder	functional interface	Builds a code structure's blocks into its box.
StructureDefinition	record	A structure built in code: a box placed on the terrain surface at the centre of chosen chunks, filled by a StructureBuilder.
StructureDefinition.Builder	class	Builds a StructureDefinition.
StructurePieceContext	interface	The box a StructureBuilder builds in, valid only during StructureBuilder.build.
TerrainGenerator	functional interface	Terrain written in code: fills each block column of new chunks.
WorldgenRegistrar	interface	Changes world generation.

BiomeDefinition

record · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public record BiomeDefinition(float temperature, float downfall, boolean precipitation, int skyColor, Optional<Integer> fogColor, int waterColor, Optional<Integer> grassColor, Optional<Integer> foliageColor, Map<GenerationStepName,List<ResourceId>> features, List<BiomeSpawn> spawns)

A biome defined in code. Poly Mod Loader writes it as biome data into its generated data pack, so it behaves exactly like a biome from a data pack: dimensions, biome tags, and /locate biome see it. Colours are 0xRRGGBB.

Component	Type	Description
temperature	float	affects snow and grass colour (plains 0.8, snowy plains 0.0)
downfall	float	affects grass and foliage colour (plains 0.4)
precipitation	boolean	whether it rains (or snows when cold)
skyColor	int	sky colour
fogColor	Optional<Integer>	fog colour, or the game's default
waterColor	int	water colour (plains 0x3f76e4)
grassColor	Optional<Integer>	grass colour, or computed from temperature and downfall
foliageColor	Optional<Integer>	leaf colour, or computed
features	Map<GenerationStepName,List<ResourceId>>	placed features per generation step
spawns	List<BiomeSpawn>	mobs that spawn naturally

builder()

public static BiomeDefinition.Builder builder()

Since 0.1.0-alpha.4 or earlier

A builder with plains-like values and no features or spawns.

Returns BiomeDefinition.Builder

BiomeDefinition.Builder

class · Since 0.1.0-alpha.4 or earlier

public static final class Builder

Builds a BiomeDefinition.

climate(float, float, boolean)

public BiomeDefinition.Builder climate(float temperature, float downfall, boolean precipitation)

Since 0.1.0-alpha.4 or earlier

Temperature (plains 0.8), downfall (plains 0.4) and whether it rains or snows.

Parameter	Type	Description
temperature	float	—
downfall	float	—
precipitation	boolean	—

Returns BiomeDefinition.Builder

skyColor(int)

public BiomeDefinition.Builder skyColor(int color)

Since 0.1.0-alpha.4 or earlier

Sky colour, 0xRRGGBB.

Parameter	Type	Description
color	int	—

Returns BiomeDefinition.Builder

fogColor(int)

public BiomeDefinition.Builder fogColor(int color)

Since 0.1.0-alpha.4 or earlier

Fog colour, 0xRRGGBB.

Parameter	Type	Description
color	int	—

Returns BiomeDefinition.Builder

waterColor(int)

public BiomeDefinition.Builder waterColor(int color)

Since 0.1.0-alpha.4 or earlier

Water colour, 0xRRGGBB.

Parameter	Type	Description
color	int	—

Returns BiomeDefinition.Builder

grassColor(int)

public BiomeDefinition.Builder grassColor(int color)

Since 0.1.0-alpha.4 or earlier

Grass colour, 0xRRGGBB, instead of one computed from the climate.

Parameter	Type	Description
color	int	—

Returns BiomeDefinition.Builder

foliageColor(int)

public BiomeDefinition.Builder foliageColor(int color)

Since 0.1.0-alpha.4 or earlier

Leaf colour, 0xRRGGBB, instead of one computed from the climate.

Parameter	Type	Description
color	int	—

Returns BiomeDefinition.Builder

feature(GenerationStepName, ResourceId)

public BiomeDefinition.Builder feature(GenerationStepName step, ResourceId placedFeature)

Since 0.1.0-alpha.4 or earlier

Adds a placed feature, such as minecraft:trees_plains, in step.

Parameter	Type	Description
step	GenerationStepName	—
placedFeature	ResourceId	—

Returns BiomeDefinition.Builder

spawn(MobCategory, ResourceId, int, int, int)

public BiomeDefinition.Builder spawn(MobCategory category, ResourceId type, int weight, int minGroup, int maxGroup)

Since 0.1.0-alpha.4 or earlier

Adds a naturally spawning mob.

Parameter	Type	Description
category	MobCategory	—
type	ResourceId	—
weight	int	—
minGroup	int	—
maxGroup	int	—

Returns BiomeDefinition.Builder

build()

public BiomeDefinition build()

Since 0.1.0-alpha.4 or earlier

Creates the definition.

Returns BiomeDefinition

BiomeSelector

interface · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public sealed interface BiomeSelector

Chooses biomes: by ID, or by biome tag such as minecraft:is_overworld.

ids(ResourceId[])

static BiomeSelector ids(ResourceId... ids)

Since 0.1.0-alpha.4 or earlier

Biomes with one of these IDs.

Parameter	Type	Description
ids	ResourceId[]	—

Returns BiomeSelector

tag(ResourceId)

static BiomeSelector tag(ResourceId tag)

Since 0.1.0-alpha.4 or earlier

Biomes in this tag.

Parameter	Type	Description
tag	ResourceId	—

Returns BiomeSelector

BiomeSelector.ById

record · Since 0.1.0-alpha.4 or earlier

public static record ById(Set<ResourceId> ids) implements BiomeSelector

Component	Type	Description
ids	Set<ResourceId>	biome IDs

Supertypes: BiomeSelector

BiomeSelector.ByTag

record · Since 0.1.0-alpha.4 or earlier

public static record ByTag(ResourceId tag) implements BiomeSelector

Component	Type	Description
tag	ResourceId	biome tag ID, without #

Supertypes: BiomeSelector

BiomeSpawn

record · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public record BiomeSpawn(MobCategory category, ResourceId type, int weight, int minGroup, int maxGroup)

A mob that spawns in a code-defined biome.

Component	Type	Description
category	MobCategory	spawn group
type	ResourceId	entity type, for example minecraft:sheep
weight	int	chance relative to other mobs of the category
minGroup	int	smallest group
maxGroup	int	largest group

CodeFeature

functional interface · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public interface CodeFeature

A placed feature written in code: a boulder, a plant patch, an ore cluster with a custom shape. Called on world generation threads while chunks generate, possibly for several chunks at once; keep all state in local variables and take randomness only from FeatureContext.random().

place(FeatureContext)

boolean place(FeatureContext context)

Since 0.1.0-alpha.4 or earlier

Places the feature around FeatureContext.origin().

Parameter	Type	Description
context	FeatureContext	—

Returns boolean — whether anything was placed

ColumnBuilder

interface · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public interface ColumnBuilder

One block column being generated; valid only during TerrainGenerator.fillColumn.

minY()

int minY()

Since 0.1.0-alpha.4 or earlier

Lowest Y of the dimension.

Returns int

maxY()

int maxY()

Since 0.1.0-alpha.4 or earlier

Highest Y of the dimension (inclusive).

Returns int

seed()

long seed()

Since 0.1.0-alpha.4 or earlier

A number derived from the world seed and the generator ID, the same for every column.

Returns long

set(int, ResourceId)

void set(int y, ResourceId block)

Since 0.1.0-alpha.4 or earlier

Sets the default state of block at y; positions outside the dimension are ignored.

Parameter	Type	Description
y	int	—
block	ResourceId	—

Throws IllegalArgumentException — for an unknown block

fill(int, int, ResourceId)

default void fill(int fromY, int toY, ResourceId block)

Since 0.1.0-alpha.4 or earlier

Sets block from fromY to toY, both inclusive.

Parameter	Type	Description
fromY	int	—
toY	int	—
block	ResourceId	—

FeatureContext

interface · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public interface FeatureContext

Where and with what a CodeFeature places blocks, valid only during CodeFeature.place. The world being generated is the chunk of the origin and its neighbours; keep blocks within 16 blocks of the origin horizontally. Positions are world coordinates.

origin()

BlockPos origin()

Since 0.1.0-alpha.4 or earlier

The position the placement chose, for example on the surface or at a random height.

Returns BlockPos

random()

RandomGenerator random()

Since 0.1.0-alpha.4 or earlier

Randomness for this placement; the same world seed and position give the same values.

Returns RandomGenerator

blockAt(BlockPos)

ResourceId blockAt(BlockPos pos)

Since 0.1.0-alpha.4 or earlier

The block at pos, without properties.

Parameter	Type	Description
pos	BlockPos	—

Returns ResourceId

isAir(BlockPos)

boolean isAir(BlockPos pos)

Since 0.1.0-alpha.4 or earlier

Whether pos is air.

Parameter	Type	Description
pos	BlockPos	—

Returns boolean

setBlock(BlockPos, ResourceId)

void setBlock(BlockPos pos, ResourceId block)

Since 0.1.0-alpha.4 or earlier

Sets the default state of block at pos.

Parameter	Type	Description
pos	BlockPos	—
block	ResourceId	—

Throws IllegalArgumentException — if block is not a block

surfaceY(int, int)

int surfaceY(int x, int z)

Since 0.1.0-alpha.4 or earlier

The y of the first air block above the terrain at x, z, as generation sees it so far.

Parameter	Type	Description
x	int	—
z	int	—

Returns int

minY()

int minY()

Since 0.1.0-alpha.4 or earlier

The lowest block y of the world.

Returns int

maxY()

int maxY()

Since 0.1.0-alpha.4 or earlier

The highest block y of the world.

Returns int

FeaturePlacement

record · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public record FeaturePlacement(int countPerChunk, int rarity, boolean onSurface, int minY, int maxY)

Where a CodeFeature is tried in each chunk: how often, and at which height. Poly Mod Loader writes it as the placed feature with the feature's ID, the same as one from a data pack.

Component	Type	Description
countPerChunk	int	tries per chunk, each at a random x and z in the chunk
rarity	int	each try happens in 1 of rarity chunks; 1 for every chunk
onSurface	boolean	whether tries start on the terrain surface; otherwise at a random y in minY..maxY
minY	int	lowest y for tries below the surface
maxY	int	highest y for tries below the surface

onSurface(int)

public static FeaturePlacement onSurface(int countPerChunk)

Since 0.1.0-alpha.4 or earlier

countPerChunk tries on the surface of each chunk.

Parameter	Type	Description
countPerChunk	int	—

Returns FeaturePlacement

atHeight(int, int, int)

public static FeaturePlacement atHeight(int countPerChunk, int minY, int maxY)

Since 0.1.0-alpha.4 or earlier

countPerChunk tries at random heights from minY to maxY in each chunk.

Parameter	Type	Description
countPerChunk	int	—
minY	int	—
maxY	int	—

Returns FeaturePlacement

rarity(int)

public FeaturePlacement rarity(int rarity)

Since 0.1.0-alpha.4 or earlier

This placement in only 1 of rarity chunks.

Parameter	Type	Description
rarity	int	—

Returns FeaturePlacement

GenerationStepName

enum · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public enum GenerationStepName

The feature placement steps of world generation, in the order the game runs them.

Constant	Description
RAW_GENERATION	—
LAKES	—
LOCAL_MODIFICATIONS	—
UNDERGROUND_STRUCTURES	—
SURFACE_STRUCTURES	—
STRONGHOLDS	—
UNDERGROUND_ORES	—
UNDERGROUND_DECORATION	—
FLUID_SPRINGS	—
VEGETAL_DECORATION	—
TOP_LAYER_MODIFICATION	—

NoiseFunction

functional interface · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public interface NoiseFunction

A density value per block position, used inside the game's noise terrain as a density function (WorldgenRegistrar.densityFunction). In the game's terrain, positive final density is solid and negative is air or water, so a function can raise, carve or reshape terrain while the game keeps its caves, aquifers, ores, surface rules and biomes.

The game computes noise terrain in cells (noise.size_horizontal × 4 by noise.size_vertical × 4 blocks) and blends the final density inside a cell, so shapes smaller than a cell come out smoothed and a surface may be a block off the exact value.

Called extremely often from several world generation threads at once: it must be fast, keep no state, and give the same value for the same position every time.

compute(int, int, int)

double compute(int x, int y, int z)

Since 0.1.0-alpha.4 or earlier

The density at block x, y, z.

Parameter	Type	Description
x	int	—
y	int	—
z	int	—

Returns double

StructureBuilder

functional interface · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public interface StructureBuilder

Builds a code structure's blocks into its box. Called on world generation threads, once per chunk the box touches (see StructurePieceContext); keep all state in local variables.

build(StructurePieceContext)

void build(StructurePieceContext context)

Since 0.1.0-alpha.4 or earlier

Writes the structure's blocks through context.

Parameter	Type	Description
context	StructurePieceContext	—

StructureDefinition

record · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public record StructureDefinition(int sizeX, int sizeY, int sizeZ, int yOffset, BiomeSelector biomes, int spacing, int separation, GenerationStepName step, boolean adaptTerrain, StructureBuilder builder)

A structure built in code: a box placed on the terrain surface at the centre of chosen chunks, filled by a StructureBuilder. Poly Mod Loader writes the structure and its structure set into the generated data pack, so /locate structure and /place structure work with its ID.

Component	Type	Description
sizeX	int	box size along x, 1–128
sizeY	int	box size along y, 1–256
sizeZ	int	box size along z, 1–128
yOffset	int	where the box's bottom is relative to the surface; negative sinks it into the ground
biomes	BiomeSelector	where it may generate
spacing	int	average distance between structures, in chunks (village 34)
separation	int	minimum distance between structures, in chunks; less than spacing
step	GenerationStepName	the generation step it is built in
adaptTerrain	boolean	whether the terrain is smoothed around it, like around a village
builder	StructureBuilder	builds its blocks

builder(int, int, int, StructureBuilder)

public static StructureDefinition.Builder builder(int sizeX, int sizeY, int sizeZ, StructureBuilder builder)

Since 0.1.0-alpha.4 or earlier

A builder for a sizeX × sizeY × sizeZ structure built by builder.

Parameter	Type	Description
sizeX	int	—
sizeY	int	—
sizeZ	int	—
builder	StructureBuilder	—

Returns StructureDefinition.Builder

StructureDefinition.Builder

class · Since 0.1.0-alpha.4 or earlier

public static final class Builder

Builds a StructureDefinition.

yOffset(int)

public StructureDefinition.Builder yOffset(int yOffset)

Since 0.1.0-alpha.4 or earlier

Raises (or with a negative value sinks) the box relative to the surface; 0 by default.

Parameter	Type	Description
yOffset	int	—

Returns StructureDefinition.Builder

biomes(BiomeSelector)

public StructureDefinition.Builder biomes(BiomeSelector biomes)

Since 0.1.0-alpha.4 or earlier

Where it may generate; every overworld biome (#minecraft:is_overworld) by default.

Parameter	Type	Description
biomes	BiomeSelector	—

Returns StructureDefinition.Builder

spacing(int, int)

public StructureDefinition.Builder spacing(int spacing, int separation)

Since 0.1.0-alpha.4 or earlier

Average and minimum distance between structures in chunks; 32 and 8 by default.

Parameter	Type	Description
spacing	int	—
separation	int	—

Returns StructureDefinition.Builder

step(GenerationStepName)

public StructureDefinition.Builder step(GenerationStepName step)

Since 0.1.0-alpha.4 or earlier

The generation step; GenerationStepName.SURFACE_STRUCTURES by default.

Parameter	Type	Description
step	GenerationStepName	—

Returns StructureDefinition.Builder

adaptTerrain()

public StructureDefinition.Builder adaptTerrain()

Since 0.1.0-alpha.4 or earlier

Smooths the terrain around the box, like around a village.

Returns StructureDefinition.Builder

build()

public StructureDefinition build()

Since 0.1.0-alpha.4 or earlier

Creates the definition; invalid values throw IllegalArgumentException.

Returns StructureDefinition

StructurePieceContext

interface · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public interface StructurePieceContext

The box a StructureBuilder builds in, valid only during StructureBuilder.build. Coordinates are relative to the box's lowest corner, from 0 to size - 1 on each axis; blocks outside the box are ignored.

A structure larger than one chunk is built chunk by chunk: the builder is called once for each chunk the box touches, with the same random() sequence each time, and only the blocks in that chunk are written. Build the same structure on every call.

origin()

BlockPos origin()

Since 0.1.0-alpha.4 or earlier

World position of the box's lowest corner.

Returns BlockPos

sizeX()

int sizeX()

Since 0.1.0-alpha.4 or earlier

Box size along x.

Returns int

sizeY()

int sizeY()

Since 0.1.0-alpha.4 or earlier

Box size along y.

Returns int

sizeZ()

int sizeZ()

Since 0.1.0-alpha.4 or earlier

Box size along z.

Returns int

random()

RandomGenerator random()

Since 0.1.0-alpha.4 or earlier

Randomness for this structure; the same on every call for the same structure.

Returns RandomGenerator

blockAt(int, int, int)

ResourceId blockAt(int x, int y, int z)

Since 0.1.0-alpha.4 or earlier

The block at a box position, without properties.

Parameter	Type	Description
x	int	—
y	int	—
z	int	—

Returns ResourceId

setBlock(int, int, int, ResourceId)

void setBlock(int x, int y, int z, ResourceId block)

Since 0.1.0-alpha.4 or earlier

Sets the default state of block at a box position.

Parameter	Type	Description
x	int	—
y	int	—
z	int	—
block	ResourceId	—

Throws IllegalArgumentException — if block is not a block

fill(int, int, int, int, int, int, ResourceId)

default void fill(int x1, int y1, int z1, int x2, int y2, int z2, ResourceId block)

Since 0.1.0-alpha.4 or earlier

Fills the box positions from (x1, y1, z1) to (x2, y2, z2), both included.

Parameter	Type	Description
x1	int	—
y1	int	—
z1	int	—
x2	int	—
y2	int	—
z2	int	—
block	ResourceId	—

TerrainGenerator

functional interface · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public interface TerrainGenerator

Terrain written in code: fills each block column of new chunks. Registered with WorldgenRegistrar.chunkGenerator, it is used by dimensions in data packs with "generator": {"type": "<mod id>:<path>", "biome_source": {...}}. Biome features (ores, trees) and structures are added afterwards by the game as for any generator.

Threads: called on the game's world generation threads, several columns at once; the code must be thread-safe and give the same column for the same position and seed.

fillColumn(int, int, ColumnBuilder)

void fillColumn(int x, int z, ColumnBuilder column)

Since 0.1.0-alpha.4 or earlier

Fills the column at world position x, z; unset blocks stay air.

Parameter	Type	Description
x	int	—
z	int	—
column	ColumnBuilder	—

seaLevel()

default int seaLevel()

Since 0.1.0-alpha.4 or earlier

Sea level of dimensions using this generator; the game spawns water mobs and fish below it.

Returns int

WorldgenRegistrar

interface · Stability PREVIEW · Since 0.1.0-alpha.4 or earlier

public interface WorldgenRegistrar

Changes world generation. The features themselves are data: put data/<mod id>/worldgen/configured_feature/*.json and placed_feature/*.json in the mod jar, in the game's format. Custom dimensions are data too (dimension/, dimension_type/). This registrar attaches placed features to existing biomes, which data alone cannot do without replacing the biome files.

When: common entrypoints. Applied every time a server loads its worlds; affects chunks generated afterwards.

addFeature(BiomeSelector, GenerationStepName, ResourceId)

void addFeature(BiomeSelector biomes, GenerationStepName step, ResourceId placedFeature)

Since 0.1.0-alpha.4 or earlier

Adds a placed feature at the end of step in every selected biome.

Parameter	Type	Description
biomes	BiomeSelector	—
step	GenerationStepName	—
placedFeature	ResourceId	ID of a placed feature from any data pack, for example the mod's own

chunkGenerator(String, TerrainGenerator)

ResourceId chunkGenerator(String path, TerrainGenerator generator)

Since 0.1.0-alpha.4 or earlier

Registers terrain written in code as generator type <mod id>:<path>, for dimensions in data packs.

Parameter	Type	Description
path	String	—
generator	TerrainGenerator	—

Returns ResourceId — the generator type ID

Throws IllegalArgumentException — for an invalid or used path (POLY-WORLDGEN-001)

biome(String, BiomeDefinition)

ResourceId biome(String path, BiomeDefinition definition)

Since 0.1.0-alpha.4 or earlier

Defines biome <mod id>:<path> in code. Use it in dimensions and biome tags like a biome from a data pack.

Parameter	Type	Description
path	String	—
definition	BiomeDefinition	—

Returns ResourceId — the biome ID

feature(String, FeaturePlacement, CodeFeature)

ResourceId feature(String path, FeaturePlacement placement, CodeFeature feature)

Since 0.1.0-alpha.4 or earlier

Registers a feature written in code as feature type <mod id>:<path>, and writes a configured and a placed feature with the same ID into Poly Mod Loader's generated data pack. Add it to biomes with addFeature, place it with /place feature <id>, or use the type in the mod's own data pack.

Parameter	Type	Description
path	String	—
placement	FeaturePlacement	—
feature	CodeFeature	—

Returns ResourceId — the feature ID

Throws IllegalArgumentException — for an invalid or used path (POLY-WORLDGEN-004)

densityFunction(String, double, double, NoiseFunction)

ResourceId densityFunction(String path, double minValue, double maxValue, NoiseFunction function)

Since 0.1.0-alpha.4 or earlier

Registers a density function written in code as type <mod id>:<path>. Data packs use it inside the game's noise terrain, for example in a noise settings' final_density: {"type": "minecraft:add", "argument1": …, "argument2": {"type": "<mod id>:<path>"}}.

Parameter	Type	Description
path	String	—
minValue	double	the lowest value function returns; the game uses the bounds to skip work
maxValue	double	the highest value function returns
function	NoiseFunction	—

Returns ResourceId — the density function type ID

Throws IllegalArgumentException — for an invalid or used path (POLY-WORLDGEN-004) or minValue > maxValue

structure(String, StructureDefinition)

ResourceId structure(String path, StructureDefinition definition)

Since 0.1.0-alpha.4 or earlier

Registers a structure built in code as <mod id>:<path>, with its structure set, in Poly Mod Loader's generated data pack. It generates in new chunks of the selected biomes; /locate structure and /place structure find and place it.

Parameter	Type	Description
path	String	—
definition	StructureDefinition	—

Returns ResourceId — the structure ID

Throws IllegalArgumentException — for an invalid or used path (POLY-WORLDGEN-004)