Minecraft 1.17: The Expanded Horizons Update

Minecraft 1.17, also known as The Expanded Horizons update, is an update that focused on making biomes more dynamic and engaging.
==Changes==
*The minecraft rendering engine now uses raytracing.
*Diffraction effects have been added to water.
*The world generation system has been changed to account for weather patterns in biome placement.
*Weather is now local rather than global, and weather systems are influenced by the heat and humidity of chunks.
*Heat and humidity are now separate from a chunk's biome.
*Polar Bears can now wear armor, although they must spawn this way and cannot be equipped by the player.
*Coral Blocks will randomly over time grow Coral Fans and Coral Plants which will randomly grow up into full Coral Blocks. Over time some areas with low populations of Parasitic Coral will develop into coral islands.
*Dead Coral will randomly become Sand if a live coral block is below it.
===Biome Assignment===
The biome of a chunk can change based on the heat and humidity value of the chunk as well as the block composition of it's surface.  Heat is determined by the heat of nearby chunks and by the average brightness of the surface blocks.  Chunks with more bright blocks like snow reflect more light and are colder, while chunks with darker blocks like dirt will absorb more light and are warmer.  Humidity is determined by the amount of water, waterlogged blocks, wet sponge, or filled cauldrons exposed to air, as well as the humidity of surrounding chunks.  Dimensions have base heat and humidity values which vary from chunk to cunk.  For all non-nether biomes aside from stone beaches a chunk must have a surface composition primairily matching that of the biome to be that biome.  Although it is possible to cause nether chunks to become overworld biomes it is incredibly difficult since water cannot be placed in the nether.
==Additions==
*Mycorrhizae Blocks, which will spread onto nearby dirt blocks that are not exposed to air.  The growth of grass, plants on the grass, and plants on farmland will increase if a Mycorrhizae block is underneath.
*Antarctictite Blocks, which generate on the seabed of frozen ocean biomes.
*Antarctictite, which drops from Antarticite Blocks when not mined with a silk touch pickaxe.
*Coldstone, an item obtained from dungeon chests in cold biomes.
*Ice resistance potion effect, which is obtained by having a coldstone in your inventory.
*Polar Lord effect.
*Parasitic Barb item.
*Dirt tunnels in jungles with zombie spawners.
*Cocoon Block.
===Antarctictite Gear===
Antarctictite can be combined with diamond gear on a smithing table just as netherite can to create Antarctictite gear.  Antarctictite gear will melt back into diamond gear if the player that is holding them or block that contains them reaches a temperature of cool or above.  Antarctictite gear will not melt in Shulker Boxes or Enderchests.  Antarctictite has better durability, protection, breaking speed, and damage than diamond, but has the same enchantability.
===Temperature===
Blocks, mobs, and the player have temperature values.  The player's temperature is determined by the temperature of the block they are standing in plus the insulation of their armor.  Leather armor provides the best insulation, followed by diamond, chainmail, netheite, antarctictite, iron, and gold.  Antarctictite, iron, and gold have negative insulation values and will cool the player down, making them ideal for trips to the nether, although antarctictite would melt instantly.  Mob temperature is determined the same way as player temperature, although many mobs have natural insulation values.  Block temperature is determined by chunk temperature plus the local heat sources and sinks.  Campfires, fire, lava, torches, lanterns, soul torches, soul campfires, soul fire, soul lanterns, magma, lit furnaces, lit blast furnaces, and lit smokers all create heat to varying degrees.  Ice, packed ice, blue ice, water, filled cauldrons, wet sponge, sea lanterns, and waterlogged blocks all absorb heat to varying degrees.  Heat sources and sinks spread their effect out over nearby blocks like lightsources, but heat blocked by an insulating block will reflect off it and increase the heat level, and heat adds rather than taking the highest number.  Wind particle effects will be created between areas of hot and cold to make spotting insulation leaks easier.  Non-insulating blocks that are leaking heat in a cold chunk will appear frosted on the warm side, and blocks with a heat value above warm will have a shimmering effect applied.  There is no onscreen overlay for temperature, rather, the players health and hunger bars will become frosted if cold and shimmer if hot.  If a player or mob has a temperature outside the range of warm to cool they will begin taking damage unless they have a fire resistance or cold resistance potion effect.
===Pole Beast===
The Pole Beast only spawns in cold biomes upon world generation, so to find a Pole Beast the player must explore new terrain.  Pole Beasts spawn surrounded by 20 to 30 adult Polar Bears, which will not attack the player unless one of them is attacked, like Zombie Piglins.  The Pole Beast will emit warning howls if the player comes within 50 blocks and will attack the player if they are visible within 15 blocks.  When the Pole Beast attacks the Polar Bears will encircle the player and become hostile if the player attempts to leave before defeating the Pole Beast.  The Pole Beast appears as a large polar bear five blocks tall with long arms that walks on its knuckles like a gorilla.  It will use swinging attacks if the player is within four blocks and biting attacks if the player is within two.  Swings deal 8 damage and bites deal 14.  The Pole Beast has 120 health and regens in the cold.  The Pole Beast will only drop raw fish when killed, but will grant the player the Polar Lord status effect which will cause all Polar Bears within 30 blocks to follow the player and attack hostile mobs or mobs that the player attacks like tamed wolves.  The effect lasts for 30 minutes before wearing off.
===Canopede===
The Canopede spawns in bamboo forests upon world generation.  The Canopede is an undead arthropod and is affected by both Smite and Bane of Arthropods.  The Canopede is only two blocks tall but is five blocks across, and can climb bamboo like scaffolding.  The Canopede prefers to remain above the player and attack with bites which inflict 5 damage and 30 seconds of poison and stomp attacks which deal 10 damage.  The Canopede appears as a giant white spider with enormous fangs with its body draped in the pelts of several Panda Bears.  The Canopede will drop the Parasitic Barb when killed, a one use item that can be used on a mob which will then spawn a baby Canopede when killed.  Baby Canopedes will attack hostile mobs until they have killed 10 hostile mobs and then they will cocoon themselves and become a Cocoon Block which if left in a warm area for 10 to 20 minutes will break and spawn an adult Canopede.
=== Parasitic Coral ===
Parasitic Coral Blocks are a red coral that does not spread which generate in low numbers in the warm ocean biome. Parasitic Coral blocks spawn Parasitic Coral, a small crab-like mob with a shell of coral. Parasitic Coral will seek out normal corals which it will then infest, despawning the mob and turning the coral into the first stage of infested coral. Infested coral will progress through five stages of infestation, taking on a texture more and more similar to Parasitic Coral Blocks until it either breaks or has a one in fifteen chance of becoming another Parasitic Coral Block. Parasitic Coral serves as a natural predator to keep growing coral populations in check.