The second Caves & Cliffs: Part II snapshot is here! This snapshot mostly contains tweaks and bug fixes, but there are also some new technical additions such as a separate simulation distance slider and an increased thread count (no I'm not talking about the fancy sheets you're thinking about buying).

Oh, and you also seemed to enjoy Strongholds quite a lot, so we decided to add them back into the game. Enjoy!

Known Issues in 21w38a

This snapshot is still not compatible with older worlds - to play in this snapshot, you will have to create a new world
World saving can sometimes take a very long time - if you see the world stop moving for a time, this is why

Changes in 21w38a

Sprinting is no longer reduced to walking when gently brushing your sleeve against a wall
Fixes for the distribution of ores

Ore distribution

Copper ore generates up to y 95 (as originally designed)
Increased the amount of copper
Lapis lazuli generates in blobs, like other ores (instead of spread out)

Sprinting

Previously, any collision with a block would reduce sprinting to walking. Now, for very minor angles of collision with a block, players retain their sprint. For larger angles of collision, the old behavior is retained.

Technical Changes in 21w38a

A new setting has been added: "Simulation distance"
Maximum amount of background threads increased
Added telemetry for world loading

Simulation distance setting

Entities will not be updated outside of simulation distance.
Allows higher render distance with less CPU load.
A new slider in video settings on the client.
A new simulation-distance property in dedicated server properties.
We will continue working on it with a goal of simulation distance also affecting block and fluid ticking.

Maximum amount of background threads increased

Various background tasks including worldgen are executed on a background thread pool. Its size equals the amount of available CPU threads minus one, but there was an upper limit of 7. Now this upper limit is 255. This should help higher-end machines with world-gen performance.

The upper limit can be overridden by max.bg.threads Java system property, for example when running multiple servers on a single machine.

Telemetry

In this release, we are re-introducing diagnostic tracking, which was part of Minecraft: Java Edition until 2018. We are bringing it back to better understand our players and to improve their experience. Specifically, we hope to ensure stronger performance for the extremely heavy world generation in the second part of the Caves & Cliffs update later this year.

In practice, this can mean identifying technical pain points in the game, like how less powerful hardware performs in high-complexity terrain. This information will also help us prioritize various aspects of development, balance game features (by learning, for instance, that the goats are pushing every single player off the cliffs) and lend new Minecrafters a helping hand (after realizing that many of them get stuck at the same points). All data is treated according to GDPR and CCPA best practices and is used to develop a better-performing and generally more enjoyable Minecraft: Java Edition.

At this point the only implemented event is world load.

World Load event

Sent when loading singleplayer world or connecting to multiplayer server
Contains following information:
- launcher identifier
- user identitifer (XUID)
- client session id (changes on restart)
- world session id (changes per world load, to be reused for later events)
- game version
- operating system name and version
- Java runtime version
- if client or server is modded (same information as on crash logs)
- server type (single player, Realms or other)
- game mode

Bugs fixed in 21w38a

MC-44055 Game fails to switch the audio output from one device to another after the game has started (from title screen)
MC-236611 No sound for using shears on weeping, twisting, cave vines or kelp
MC-236618 Strongholds don't generate in 21w37a
- MC-236621 Liquids sometimes do not propagate
MC-236633 Random light level of 0 in sky
MC-236656 Crash when changing render distance / java.lang.ArrayIndexOutOfBoundsException: Index 28084 out of bounds for length 26136
MC-236665 Memory leak in 21w37a
MC-236698 Big Spruce Trees don't generate in Groves
MC-236711 Starting and stopping JFR profiling multiple times within the same minute overwrites previous JFR results saved during that minute
MC-236718 Dripstone caves generate above the ground
MC-236795 Cannot start with alternate JVM due to JFR requirement
MC-236873 Problems with JFR event metadata
MC-236967 Too many aquifers on biome surfaces at Y=63 and below
MC-237109 Aquifers often generate with harsh straight borders

Minecraft Snapshot 21w38a