JSPrismarine

API reference / @jsprismarine/features / WorldgenRandom

Class: WorldgenRandom ​

Defined in: placement/WorldgenRandom.ts:37

Java Edition's WorldgenRandom: a reseedable stream, plus the four seed derivations world generation keys off.

It is not simply one of @jsprismarine/worldgen's two sources. Java's class extends LegacyRandomSource and overrides only next(bits), so every derived draw -- nextInt, nextFloat, nextDouble, nextGaussian -- uses java.util.Random's formulas over a Xoroshiro bit stream. Handing a feature a plain XoroshiroRandomSource produces different numbers from the first float onward, which is why this class exists rather than a helper.

The seed derivations matter more than they look. Every feature placed in a chunk draws from a stream seeded by the chunk's population seed, the feature's index in the flattened per-step list and its decoration step. That is what makes a world reproducible: two servers that agree on the seed, the chunk and the feature list place the same blocks, in any order, on any number of threads.

Implements ​

Constructors ​

Constructor ​

new WorldgenRandom(seed?, algorithm?): WorldgenRandom

Defined in: placement/WorldgenRandom.ts:50

Parameters ​

seed? ​

bigint = 0n

The initial seed. The chunk generator's value is discarded by the first setDecorationSeed, so it only matters for a stream used directly.

algorithm? ​

WorldgenRandomAlgorithm = 'xoroshiro'

The backing generator. Defaults to Xoroshiro, which is what ChunkGenerator.applyBiomeDecoration builds.

Returns ​

WorldgenRandom

Methods ​

consumeCount() ​

consumeCount(rounds): void

Defined in: placement/WorldgenRandom.ts:208

Advances the stream by rounds draws without returning them.

Parameters ​

rounds ​

number

Returns ​

void

Implementation of ​

RandomSource.consumeCount

fork() ​

fork(): RandomSource

Defined in: placement/WorldgenRandom.ts:213

Returns an independent stream seeded from this one, advancing this one.

Returns ​

RandomSource

Implementation of ​

RandomSource.fork

forkPositional() ​

forkPositional(): PositionalRandomFactory

Defined in: placement/WorldgenRandom.ts:218

Returns a positional factory seeded from this stream, advancing it.

Returns ​

PositionalRandomFactory

Implementation of ​

RandomSource.forkPositional

next() ​

next(bits): number

Defined in: placement/WorldgenRandom.ts:150

Returns the top bits bits of the backing stream, as Java's next(int) does.

Parameters ​

bits ​

number

Returns ​

number

nextBoolean() ​

nextBoolean(): boolean

Defined in: placement/WorldgenRandom.ts:185

Returns the next boolean, taken from one bit of the stream.

Returns ​

boolean

Implementation of ​

RandomSource.nextBoolean

nextDouble() ​

nextDouble(): number

Defined in: placement/WorldgenRandom.ts:195

Returns the next value in [0, 1) with 53 bits of precision.

Returns ​

number

Implementation of ​

RandomSource.nextDouble

nextFloat() ​

nextFloat(): number

Defined in: placement/WorldgenRandom.ts:190

Returns the next value in [0, 1) with 24 bits of precision.

Returns ​

number

Implementation of ​

RandomSource.nextFloat

nextGaussian() ​

nextGaussian(): number

Defined in: placement/WorldgenRandom.ts:203

Returns the next normally distributed value with mean 0 and standard deviation 1.

Returns ​

number

Implementation of ​

RandomSource.nextGaussian

nextInt() ​

nextInt(): number

Defined in: placement/WorldgenRandom.ts:157

Returns the next 32-bit signed integer, with every value equally likely.

Returns ​

number

Implementation of ​

RandomSource.nextInt

nextIntBounded() ​

nextIntBounded(bound): number

Defined in: placement/WorldgenRandom.ts:162

Returns the next integer in [0, bound).

Parameters ​

bound ​

number

Returns ​

number

Throws ​

When bound is not positive, as Java does.

Implementation of ​

RandomSource.nextIntBounded

nextLong() ​

nextLong(): bigint

Defined in: placement/WorldgenRandom.ts:178

Returns the next 64-bit signed integer.

Returns ​

bigint

Implementation of ​

RandomSource.nextLong

restoreState() ​

restoreState(state): void

Defined in: placement/WorldgenRandom.ts:73

Restores a state produced by saveState, including Java's cached Gaussian value.

Parameters ​

state ​

unknown

Returns ​

void

saveState() ​

saveState(): WorldgenRandomState

Defined in: placement/WorldgenRandom.ts:60

Captures the backing stream and Java's separately cached Gaussian value.

Returns ​

WorldgenRandomState

setDecorationSeed() ​

setDecorationSeed(levelSeed, minBlockX, minBlockZ): bigint

Defined in: placement/WorldgenRandom.ts:114

Derives and applies a chunk's population seed, then returns it.

Parameters ​

levelSeed ​

bigint

The world seed.

minBlockX ​

number

The x of the chunk's lowest-numbered block, not its chunk coordinate.

minBlockZ ​

number

The z of the chunk's lowest-numbered block.

Returns ​

bigint

setFeatureSeed() ​

setFeatureSeed(populationSeed, index, step): void

Defined in: placement/WorldgenRandom.ts:130

Applies the stream one placed feature draws from.

Parameters ​

populationSeed ​

bigint

The value setDecorationSeed returned.

index ​

number

The feature's index within the flattened per-step feature list.

step ​

number

The decoration step's ordinal, 0 through 10.

Returns ​

void

setLargeFeatureSeed() ​

setLargeFeatureSeed(baseSeed, chunkX, chunkZ): void

Defined in: placement/WorldgenRandom.ts:135

Applies the stream a structure start draws from, keyed by chunk.

Parameters ​

baseSeed ​

bigint

chunkX ​

number

chunkZ ​

number

Returns ​

void

setLargeFeatureWithSalt() ​

setLargeFeatureWithSalt(levelSeed, regionX, regionZ, salt): void

Defined in: placement/WorldgenRandom.ts:143

Applies the salted stream the region-based structure placements draw from.

Parameters ​

levelSeed ​

bigint

regionX ​

number

regionZ ​

number

salt ​

number

Returns ​

void

setSeed() ​

setSeed(seed): void

Defined in: placement/WorldgenRandom.ts:103

Restarts the stream from a seed, as Java's setSeed does.

Parameters ​

seed ​

bigint

Returns ​

void