A truly fabulous snapshot enters the arena! This snapshot brings fundamental changes to our rendering pipeline with the introduction of the brand new tech that is OpenGL Core 3.2. On top of that, we're finally introducing the Lush Caves biome. However, as with the Dripstone Caves, this is only available through creating a custom world.

There's an important note about this snapshot for those of you with older computers: With the introduction of OpenGL Core 3.2 there is a chance Minecraft Java will no longer run on computers that do not meet the minimum system requirements. Computers that meet the minimum system requirements should not be affected.

New Features in 21w10a

Added Lush Caves underground biome!
Added Cracked Deepslate Bricks and Cracked Deepslate Tiles
There is now an Infested variant of Deepslate found in the underground
While they will not generate in the world by default, Deepslate versions of copper, emerald and coal ores have been added for use by creators of maps and data packs

Lush caves biome

The Lush Caves underground biome now exists for use in single-biome worlds. It does not yet generate in other world types.

Moss covers the floors and ceilings
Spore Blossoms grow from the ceiling and drip particles
Contains clay pools with dripleaf plants grow out of them
Contains azalea bushes and flowering azalea bushes
The azalea tree loves to have its roots in lush caves, so if you find an azalea tree (either overground or in a cave) you know there is a lush cave beneath you
Cave vines with glow berries grow from the ceiling and light up the caves

Changes in 21w10a

Cobbled Deepslate can now be smelted into Deepslate.
Deepslate can now be placed along any axis
Lightning rods can now be waterlogged
Fossils in the deepest part of the underground generate with deepslate diamond ore instead of coal ore
Some ore textures have been updated

Minecraft Snapshot 21w10a texture comparison (cropped)

Ore texture changes in snapshot 21w10a. Click here for a link to the full resolution image.

Minecraft Snapshot 21w10a texture comparison 2 (cropped)

New textures for emerald, coal, and copper in Deepslate. Click here for a link to the full resolution image.

Ore distribution

Overworld ore generation has been tweaked.

More emeralds in mountains
More lapis
Less copper, gold, and redstone
Smaller diamond blobs, but slightly more frequent. Less diamond ore overall though
Less iron, and it generates lower down
Reduced air exposure for coal

Minecraft Snapshot 21w10a ores distribution (cropped)

Ore distribution in snapshot 21w10a. Click here for a link to the full resolution image.

Technical Changes in 21w10a

The game now runs using OpenGL 3.2 core profile
The maximum size that slimes can be summoned with is now 128
The give command can only give up to 100 stacks of items at a time (e.g. 6400 stone or 100 iron swords)

OpenGL

Rendering is now using OpenGL 3.2 core profile. All fixed function rendering has been replaced with shader based rendering.

Shaders

Shaders are now included for all supported render states. Any shader except for the blit shader can also be replaced in resource packs. For now replacing these shaders is not officially supported and the way it works may change in the future.

The current rendering engine uses a system similar to the post processing shader pipeline. There are some differences between both system that cater to the slightly different requirements.

Bugs fixed in 21w10a

MC-29318 Client misses inventory updates while player is manipulating items causes invisible items
MC-84121 Shape of glow effect is based on mob's base layer
MC-87019 Only visible slots are updated clientside when you are inside an inventory
MC-154094 Lectern running /clear turns items into ghost items
MC-175964 Setblock command run by book in lectern to clear inventory run in command block causes ghost items
MC-201316 The /give command can create so many items that the game will freeze
MC-207818 Placing a sign from the offhand closes the sign UI immediately
MC-208301 /clear does not properly affect the item on the mouse pointer after crafting it
MC-210408 /spawnpoint allows players to set their spawnpoint to out-of-bounds coordinates, which crashes the game when trying to respawn
MC-211666 Guardians attack invisible axolotls
MC-212127 Normal ink sac and glow ink sac are not grouped in the creative inventory
MC-212144 Subtitles refer to Glow Item Frame as "Item Frame"
MC-212168 Ctrl + Pick Block doesn't copy block state "lit"
MC-212236 Cannot visually critical-hit a glow squid (No sound/particles)
MC-212314 Glow squid remains dark even if there is a light source block next to it
MC-212325 Glow Squid entity data (potion effects, custom name, ...) does not get saved
MC-214629 FOV decreases when underwater regardless of FOV Effects accessibility setting
MC-214781 Lava does not generate at the very bottom of noise caves
MC-214784 Fossils can generate floating in caves
MC-214836 Water caves cause land to be excessively flooded
MC-214844 Bedrock can be exposed to the air at the very bottom of the new caves
MC-214970 Phantoms continously make too much flapping sounds
MC-215194 Structure blocks do not work below y=0
MC-215838 There is currently no way to craft deepslate tiles and deepslate bricks
MC-215850 Deepslate Tile Wall comes before Deepslate Brick Wall but Deepslate Bricks come before Deepslate Tiles in creative inventory
MC-215939 Emerald ore spawns in lower frequencies than it should above y=100
MC-216136 Polished deepslate slab isn't grouped with the other deepslate slabs in creative inventory
MC-216363 Crash upon replacing soul sand or magma with the other under a tall bubble column using /setblock
MC-216735 Stone Lapis Ore generating in Deepslate
MC-216736 Lava lakes generate exposed in caves
MC-216765 Coal ore can generate below Y=0 when attached to a fossil
MC-216817 Inconsistency: Cobbled deepslate cannot be smelted back into deepslate
MC-218139 Spectator vision bug