Package net.minecraft.world.gen

Class ChunkRandom

java.lang.Object

java.util.Random

net.minecraft.world.gen.ChunkRandom

All Implemented Interfaces:

Serializable

public class ChunkRandom
extends Random

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
ChunkRandom()
ChunkRandom(long seed)

Method Summary

Modifier and Type	Method	Description
void	consume(int count)	Skips the provided number of calls to the randomizer.
static Random	getSlimeRandom(int chunkX, int chunkZ, long worldSeed, long scrambler)
long	setCarverSeed(long worldSeed, int chunkX, int chunkZ)	Seeds the randomizer to generate larger features such as caves, ravines, mineshafts and strongholds.
long	setDecoratorSeed(long populationSeed, int index, int step)	Seeds the randomizer to generate a given feature.
long	setPopulationSeed(long worldSeed, int blockX, int blockZ)	Seeds the randomizer to create population features such as decorators and animals.
long	setRegionSeed(long worldSeed, int regionX, int regionZ, int salt)	Seeds the randomizer to determine the start position of structure features such as temples, monuments and buried treasures within a region.
long	setTerrainSeed(int chunkX, int chunkZ)	Seeds the randomizer to generate the surface terrain blocks (such as grass, sand, etc.) and the bedrock patterns.

Methods inherited from class java.util.Random

doubles, doubles, doubles, doubles, ints, ints, ints, ints, longs, longs, longs, longs, next, nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextInt, nextLong, setSeed

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ChunkRandom

public ChunkRandom()

ChunkRandom

public ChunkRandom(long seed)

Method Details

consume

public void consume(int count)

Skips the provided number of calls to the randomizer.

The skips give the effect of "scrambling" the randomizer but the output is still linearly dependent. Note that since multiple calls to a linear congruential generator is equivalent to another linear congruence, this method could be optimized to combine the calls into one.

setTerrainSeed

public long setTerrainSeed(int chunkX,
int chunkZ)

Seeds the randomizer to generate the surface terrain blocks (such as grass, sand, etc.) and the bedrock patterns.

Note that the terrain seed does not depend on the world seed and only gets affected by chunk coordinates.

setPopulationSeed

public long setPopulationSeed(long worldSeed,
int blockX,
int blockZ)

Seeds the randomizer to create population features such as decorators and animals.

This method takes in the world seed and the negative-most block coordinates of the chunk. The coordinate pair provided is equivalent to (chunkX * 16, chunkZ * 16). The three values are mixed together through some layers of hashing to produce the population seed.

This function has been proved to be reversible through some exploitation of the underlying nextLong() weaknesses. It is also important to remember that since setSeed() truncates the 16 upper bits of world seed, only the 48 lowest bits affect the population seed output.

setDecoratorSeed

public long setDecoratorSeed(long populationSeed,
int index,
int step)

Seeds the randomizer to generate a given feature. The salt, in the form of index + 10000 * step assures that each feature is seeded differently, making the decoration feel more random. Even though it does a good job at doing so, many entropy issues arise from the salt being so small and result in weird alignments between features that have an index close apart.

Parameters:

populationSeed - The population seed computed in setPopulationSeed().

index - The index of the feature in the feature list.

step - The generation step's ordinal for this feature.

setCarverSeed

public long setCarverSeed(long worldSeed,
int chunkX,
int chunkZ)

Seeds the randomizer to generate larger features such as caves, ravines, mineshafts and strongholds. It is also used to initiate structure start behavior such as rotation.

Similar to the population seed, only the 48 lowest bits of the world seed affect the output since it the upper 16 bits are truncated in the setSeed() call.

setRegionSeed

public long setRegionSeed(long worldSeed,
int regionX,
int regionZ,
int salt)

Seeds the randomizer to determine the start position of structure features such as temples, monuments and buried treasures within a region.

The region coordinates pair corresponds to the coordinates of the region the seeded chunk lies in. For example, a swamp hut region is 32 by 32 chunks meaning that all chunks that lie within that region get seeded the same way.

Similarly, the upper 16 bits of world seed also do not affect the region seed because they get truncated in the setSeed() call.

getSlimeRandom

public static Random getSlimeRandom(int chunkX,
int chunkZ,
long worldSeed,
long scrambler)