I feel like there isn't enough stuff underground to keep people going back after they no longer need to. I feel that they should make 1.17.0 the Cave Update. They should add mobs that only spawn underground to keep people going down there, even after they find a couple stacks of diamonds. They should also add more ores. Nothing better than diamond, but maybe something like rubies or amethysts to make it less painful and boring to find ores. Maybe they could even add something like a metal detector! It would tell you whether or not there are ores nearby. Maybe it would go in your offhand and it would put something extra in your HUD.
That said, I would structure it around cave "biomes" with generated structures.
Biomes entrain themselves to the Overworld and generate designate the "base" block of the caves as well as the frequency with which given ores and structures spawn. These don't have to be a 100% thing either--for example, in deserts, there's a chance for the subterranean to either be primarily Sandstone or primarily Rock. So, your underground biome could be "Desert Sandstone Caves" or "Desert Rock Caves." This is already done to an extent, but it doesn't really affect much other than some ore weights and structures weights. Using this method, you could also introduce a variety of new "base" cave blocks, such as Limestone, Peridotite, Pumice (for some Overworld volcanic regions), Chalk, Marble, Jaspilite, or Slate, etc.
Then, with structures, introduce more "natural" structures into cave generation. Things like.... grottos, stalagmites and stalactites, some underground animal/plantlife (i.e. the mushroom grotto in the picture you include).
I agree that new ores (or more broadly, materials) should be added, but keep in mind they need a purpose. While aesthetic is a decent-enough reason to add a couple of items, a large-scale update like this would need some core functions. I don't dislike the idea of a Metal Detector, but perhaps that functionality could be tied to a Potion which is made with some new material found in the updated caves.
This would be a great opportunity to expand the sub terrain environment beyond Y 0 and move bedrock and the void further down. I figure if Mojang were to make cave systems and abandoned mineshafts and dungeons more interesting they first in my opinion should introduce something similar to cubic chunks in the vanilla game.
Instead of making ores more common and therefore making obtaining precious gemstones and materials too easy and unbalanced, they should instead make the underground section of Minecraft worlds thicker, yes there would be more ores to obtain, but you also put in extra work to obtain them. I say keep the ore rarity/common-ness or distribution the same as they are now, but with much deeper ground, perhaps with more lava the deeper you go to make it more hazardous and harder to obtain the diamonds, before mining the diamonds you first need to clear out the lava to stop ore drops being destroyed.
The new bedrock layer could be extended to Y -2048 to -2053.
It is Minecraft after all, and what better way to improve the game than focusing more of the gameplay design on the mining aspect? you want more iron? redstone? lapis? great, but then get back into the mining tunnels and get collecting and enjoy yourself.
Also with deeper ground environments this would be a good reason to add more ore types too.
I've pretty much made my own "cave update"; for one, I'd revert the changes made to the underground in 1.7, which made cave systems much less dense and much less varied in size (in 1.6 the "size" of a cave system varied from 1-39 but in 1.7+ it only ranges from 1-14), as well as mineshafts and dungeons much less common. However, I wouldn't entirely revert mineshafts; instead they generate using a system similar to structures like villages, where the game divides the world into 32x32 chunk regions with one village randomly located within each region, except mineshafts use a much smaller grid size, which prevents them from intersecting other mineshafts (they can even generate in adjacent chunks in vanilla) and whether one generates is dependent on the local cave density so they don't generate in areas of high cave density.
Caves would also vary a lot more, with regional variations in various generation parameters, such as the width of tunnels, size of rooms, how straight or curved tunnels are, tunnel length, and more. There would also be less common variants of caves and ravines that can become much larger, as well as cave systems with different cave variations, such as "ravine cave systems" made up of small ravines instead of tunnels/rooms, "circular room cave systems" made up of circular rooms (the round rooms you often find in caves), "maze cave systems" made up of caves which generate like mazes (multiple branches), and so on, even rare "colossal cave systems" base dona cave system in my first world (these are extremely rare in vanilla prior to 1.6; they would still be relatively uncommon but there would also be at least one within a reasonable distance of spawn) and even "giant cave regions" areas of many large caves intersecting to form a vast underground structure more akin to the Nether than a typical Overworld cave.
If all of this sounds highly specific, this is because this describes the underground of "TheMasterCaver's World", my alternative to updating to newer vanilla versions since 2014:
Here are more detailed maps (click to enlarge, the scale is 1 block per pixel or 2048x2048 blocks) of only special variants of caves and mineshafts/strongholds:
A small stronghold is visible near the lower-right (in TMCWv5 they will have a minimum size of 100 structure pieces, where most strongholds are above this). If mineshafts seem common here, they are actually only about 60% as common as in vanilla 1.6, but 50% more common than in 1.7 and later (their base generation chance is about the same as vanilla 1.6 but about 40% fail to generate as the local cave density is too high, or there is a large cave/ravine/special cave system nearby); they also a larger size variation than in vanilla:
These maps also do not show additional features being added in a future update, including enhancements to "underground biomes", where the underground takes on some of the characteristics of the surface, such as deserts having sandstone and sand in place of stone and dirt/gravel (currently this layer only extends down to around y=40, I plan to replace all stone down to bedrock, which is just one layer with cave lava level lowered to y=4 to make more use of the underground, and ores will have textures that match the blocks, e.g. sandstone-based textures in deserts):
A ravine in a mesa biome; the hardened clay layers extend below the surface and ores can generate in them with the texture of hardened clay; you can also see stalagmites and stalactites of various colors (based on the block they re on):
A mesa mineshaft, similar to those in later vanilla versions, except the center room has red clay (a functionally identical variant of the gray clay found in vanilla); unlike vanilla, which simply adds more gold above y=32, extra gold only generates as part of surface mineshafts:
A cave in an Ice Hills biome (unique to TMCW), which replaces stone with packed ice and snow (the floors of caves have a mix of both, they can still be quite slippery):
This is the rest of the same cave shown above:
If that seems big, this cave has a volume of about 685,000 blocks, some 30 times larger than the largest single cave in vanilla:
This shows more underground decorations; there are more colors of mushrooms and variants of huge mushrooms; you can also see pockets of clay as this is in a swamp, which also have more water lakes and springs underground:
Yes, that's a stray near the center - I have no idea why they should only be able to spawn at the surface, making them totally pointless as I'd practically never see then, same for husks. Cave spiders and silverfish also naturally spawn below sea level (silverfish can only enter blocks if they came from infested blocks or spawners). You can also see that gravel can generate with both the vanilla texture as well as the old Beta texture (which I call "gravel sand" as it looks a lot like the sand texture, basically like much finer gravel), with the chance of each type varying on a regional scale (some areas have more normal gravel, others less. The 1.8 stone variants also vary in such a manner, so some areas mostly have granite while others have very little):
A ravine in a Mega Taiga; notice that the exposed dirt is podzol, the mineshaft is also made of spruce wood, which matches the type(s) of trees found, generally oak in biomes without trees (some biomes can have multiple types of wood, with any one mineshaft having one type):
A cave in a quartz desert (another biome unique to TMCW):
A cave in an Iceland biome:
Volcanic Wasteland, which reverses normal stone with andesite (pockets of normal stone generate in andesite) and adds pockets of magma blocks and greatly increases the number of lava lakes and springs with a complete lack of water outside of rivers. Ores are also more common in this biome, offset by the increase in lava and its rarity, and magma cubes spawn in place of slimes (slimes in general will spawn magma cubes if they die in lava):
A jungle cave, which is exclusively found under jungles:
Caves in jungles otherwise have more vegetation:
Caves in Mushroom Island have mycelium on the floor, as well as more mushrooms, including huge mushrooms in larger caves (they also generate elsewhere but much less commonly):
A ravine in a desert:
A ravine in Badlands (not the same as vanilla's "badlands" aka mesa biome):
A huge cave and ravine in a desert:
There are also more variants of husks to match the biome; in this case, red husks in a mesa biome:
This shows some of the many variants of ores, which use a transparent overlay that is overlaid on a base texture (I only had to make a single texture for each ore, which are overlaid at render time, similar to the side of grass blocks):
Likewise, these are all the variants of stalagmites and stalactites (note that I've since added a random offset, similar to tall grass, so they don't form such a regular pattern):
Also, there are an unlimited number of strongholds in the world, similar to Bedrock (but every one has a portal!) with one generating every 8192 chunks, and caves do not "cut" them apart (they don't in any case, in vanilla the walls do not overwrite air), which will also apply to mineshafts in the future (all parts, not just corridors):
A stronghold that generated in an enormous cave; the only openings in the walls are at dead ends (where corridors otherwise run into stone):
Notice that the central room (the area with a dirt floor) and staircases generated planks below them (mineshafts in vanilla have been very buggy since 1.10 due to a poorly implemented way to prevent mineshafts from generating above the surface unless they are buried, which is applied to all mineshafts, my method instead checks the height of the surface and only affects mineshafts above sea level).
Dungeons are more varied, with most Overworld mobs able to spawn, as well as "double dungeons" which have 2 spawners, each spawning a different type of mob, and 2-3 chests. They are also much more of a challeng as they spawn mobs at a much faster rate, balanced out by the fact that there is a "cooldown" that disables item and XP drops if too many mobs spawn too quickly (preventing exploits, aka "mob farms"); spawners themselves are immune to creeper explosions (yes, there are creeper spawners) and can be mined with Silk Touch to obtain an "empty spawner" for decorative purposes (using a flint and steel on them will cause them to emit spawner particles and light):
You certainly never want to just run into a dungeon when they can spawn more than just zombies/spiders/skeletons:
The addition of "double dungeons" also makes it possible to find crazier things than in vanilla when they merge with other dungeons; for example, this is a double dungeon intersecting a normal dungeon for a total of 3 spawners:
Mining a monster spawner with Silk Touch drops an empty spawner block; the XP also still drops as this is a separate block:
An empty monster spawner after using a flint and steel on it:
Strongholds are also more exciting to explore as they have additional spawners in the libraries (silverfish) and under the chests in hallways:
In addition, what about a way to make maps of the caves you've explored? One way to do this is to only map areas lit up by player-placed torches (with structures using a different block); only areas that have been explored will show up, with higher caves overlapping caves deeper down:
(the following images show torches as yellow dots, which I've since removed from cave maps, as shown above)
Cave maps even work in the Nether, providing a way to map it; this also shows how they work in more detail, notice the single torch to the south of the player marker, which reveals the ground if the light level is at least 6 and there is a direct path to the torch within the range (walls will block it):
I even added a new tier of tools and armor, amethyst, which has many similarities to Netherite (slightly better than diamond, which was nerfed, somewhat like how 1.9 nerfed armor by adding armor penetration, though I just reduced the general protection, only for players though so amethyst is actually stronger than diamond in vanilla 1.6.4 when worn by mobs. Durability is triple that of diamond, even more for (vanilla) armor as I made armor have a similar durability as tools but repair costs are much higher) except it is found in the Overworld at 1/8 the rate of diamond in caves:
This is a chart I made of ore distribution; diamond and amethyst generate up to layer 8 instead of 15 since cave lava level (shaded red) was lowered to y=4, or the lowest 3 layers above bedrock at layer 0. The increase on layer 1 is to encourage players to branch-mine at a level they otherwise wouldn't (below lava level) and so I can find enough in a reasonable amount of time before I start caving (I only cave at the "end-game", branch-mining to collect resources before then):
Also, Mojang absolutely has to fix the following bugs before making a "cave update" (all of these have been fixed in TMCW; TMCWv5 will even use a true 64 bit RNG so every seed has unique cave generation, at least, as far as I can tell; in vanilla every seed is one of 65536 that are identical underground):
The "chunk seed" algorithm used by caves and some other features is quite broken (there are many issues here, ranging from the fact that certain seeds completely break cave generation (cause them to repeat at some interval) to the fact that most if not all seeds have identical caves at sign-reversed coordinate pairs, with 1/3 of all seeds having 1/3 of such pairs matching, which would become very obvious if uniquely large caves are added).
As a bonus, my custom 64 bit RNG is also far faster (7-8x) than Java's Random, so much in fact that by simply replacing Random with a functionally identical replica I more than halved cave generation time, one of the most time consuming parts of world generation; this and other optimizations also offset all of the increased complexity (it took less than 10 seconds to generate the map shown above, which is 16384 chunks, using a single thread; I used a separate mapping utility I made but it uses the same cave generation code as the game itself).
I also think that caves in oceans should NOT be flooded, which makes them not even "caves" in my opinion (as it is, I already prefer exploring under land and even modified world generation to make the area around the origin always land); I even made it so that floating sand/gravel are replaced with sandstone//cobblestone so they don't cave in (there are more water lakes and springs in ocean, as well as several other "wet" biomes like swamps):
Notice the ceiling at the top, which is below the seafloor, with patches of sand and gravel in dirt (I've since replaced stone with cobblestone so that underground gravel can't replace it and collapse):
I've pretty much made my own "cave update"; for one, I'd revert the changes made to the underground in 1.7, which made cave systems much less dense and much less varied in size (in 1.6 the "size" of a cave system varied from 1-39 but in 1.7+ it only ranges from 1-14), as well as mineshafts and dungeons much less common. However, I wouldn't entirely revert mineshafts; instead they generate using a system similar to structures like villages, where the game divides the world into 32x32 chunk regions with one village randomly located within each region, except mineshafts use a much smaller grid size, which prevents them from intersecting other mineshafts (they can even generate in adjacent chunks in vanilla) and whether one generates is dependent on the local cave density so they don't generate in areas of high cave density.
Caves would also vary a lot more, with regional variations in various generation parameters, such as the width of tunnels, size of rooms, how straight or curved tunnels are, tunnel length, and more. There would also be less common variants of caves and ravines that can become much larger, as well as cave systems with different cave variations, such as "ravine cave systems" made up of small ravines instead of tunnels/rooms, "circular room cave systems" made up of circular rooms (the round rooms you often find in caves), "maze cave systems" made up of caves which generate like mazes (multiple branches), and so on, even rare "colossal cave systems" base dona cave system in my first world (these are extremely rare in vanilla prior to 1.6; they would still be relatively uncommon but there would also be at least one within a reasonable distance of spawn) and even "giant cave regions" areas of many large caves intersecting to form a vast underground structure more akin to the Nether than a typical Overworld cave.
If all of this sounds highly specific, this is because this describes the underground of "TheMasterCaver's World", my alternative to updating to newer vanilla versions since 2014:
Here are more detailed maps (click to enlarge, the scale is 1 block per pixel or 2048x2048 blocks) of only special variants of caves and mineshafts/strongholds:
A small stronghold is visible near the lower-right (in TMCWv5 they will have a minimum size of 100 structure pieces, where most strongholds are above this). If mineshafts seem common here, they are actually only about 60% as common as in vanilla 1.6, but 50% more common than in 1.7 and later (their base generation chance is about the same as vanilla 1.6 but about 40% fail to generate as the local cave density is too high, or there is a large cave/ravine/special cave system nearby); they also a larger size variation than in vanilla:
These maps also do not show additional features being added in a future update, including enhancements to "underground biomes", where the underground takes on some of the characteristics of the surface, such as deserts having sandstone and sand in place of stone and dirt/gravel (currently this layer only extends down to around y=40, I plan to replace all stone down to bedrock, which is just one layer with cave lava level lowered to y=4 to make more use of the underground, and ores will have textures that match the blocks, e.g. sandstone-based textures in deserts):
A ravine in a mesa biome; the hardened clay layers extend below the surface and ores can generate in them with the texture of hardened clay; you can also see stalagmites and stalactites of various colors (based on the block they re on):
A mesa mineshaft, similar to those in later vanilla versions, except the center room has red clay (a functionally identical variant of the gray clay found in vanilla); unlike vanilla, which simply adds more gold above y=32, extra gold only generates as part of surface mineshafts:
A cave in an Ice Hills biome (unique to TMCW), which replaces stone with packed ice and snow (the floors of caves have a mix of both, they can still be quite slippery):
This is the rest of the same cave shown above:
If that seems big, this cave has a volume of about 685,000 blocks, some 30 times larger than the largest single cave in vanilla:
This shows more underground decorations; there are more colors of mushrooms and variants of huge mushrooms; you can also see pockets of clay as this is in a swamp, which also have more water lakes and springs underground:
Yes, that's a stray near the center - I have no idea why they should only be able to spawn at the surface, making them totally pointless as I'd practically never see then, same for husks. Cave spiders and silverfish also naturally spawn below sea level (silverfish can only enter blocks if they came from infested blocks or spawners). You can also see that gravel can generate with both the vanilla texture as well as the old Beta texture (which I call "gravel sand" as it looks a lot like the sand texture, basically like much finer gravel), with the chance of each type varying on a regional scale (some areas have more normal gravel, others less. The 1.8 stone variants also vary in such a manner, so some areas mostly have granite while others have very little):
A ravine in a Mega Taiga; notice that the exposed dirt is podzol, the mineshaft is also made of spruce wood, which matches the type(s) of trees found, generally oak in biomes without trees (some biomes can have multiple types of wood, with any one mineshaft having one type):
A cave in a quartz desert (another biome unique to TMCW):
A cave in an Iceland biome:
Volcanic Wasteland, which reverses normal stone with andesite (pockets of normal stone generate in andesite) and adds pockets of magma blocks and greatly increases the number of lava lakes and springs with a complete lack of water outside of rivers. Ores are also more common in this biome, offset by the increase in lava and its rarity, and magma cubes spawn in place of slimes (slimes in general will spawn magma cubes if they die in lava):
A jungle cave, which is exclusively found under jungles:
Caves in jungles otherwise have more vegetation:
Caves in Mushroom Island have mycelium on the floor, as well as more mushrooms, including huge mushrooms in larger caves (they also generate elsewhere but much less commonly):
A ravine in a desert:
A ravine in Badlands (not the same as vanilla's "badlands" aka mesa biome):
A huge cave and ravine in a desert:
There are also more variants of husks to match the biome; in this case, red husks in a mesa biome:
This shows some of the many variants of ores, which use a transparent overlay that is overlaid on a base texture (I only had to make a single texture for each ore, which are overlaid at render time, similar to the side of grass blocks):
Likewise, these are all the variants of stalagmites and stalactites (note that I've since added a random offset, similar to tall grass, so they don't form such a regular pattern):
Also, there are an unlimited number of strongholds in the world, similar to Bedrock (but every one has a portal!) with one generating every 8192 chunks, and caves do not "cut" them apart (they don't in any case, in vanilla the walls do not overwrite air), which will also apply to mineshafts in the future (all parts, not just corridors):
A stronghold that generated in an enormous cave; the only openings in the walls are at dead ends (where corridors otherwise run into stone):
Notice that the central room (the area with a dirt floor) and staircases generated planks below them (mineshafts in vanilla have been very buggy since 1.10 due to a poorly implemented way to prevent mineshafts from generating above the surface unless they are buried, which is applied to all mineshafts, my method instead checks the height of the surface and only affects mineshafts above sea level).
Dungeons are more varied, with most Overworld mobs able to spawn, as well as "double dungeons" which have 2 spawners, each spawning a different type of mob, and 2-3 chests. They are also much more of a challeng as they spawn mobs at a much faster rate, balanced out by the fact that there is a "cooldown" that disables item and XP drops if too many mobs spawn too quickly (preventing exploits, aka "mob farms"); spawners themselves are immune to creeper explosions (yes, there are creeper spawners) and can be mined with Silk Touch to obtain an "empty spawner" for decorative purposes (using a flint and steel on them will cause them to emit spawner particles and light):
You certainly never want to just run into a dungeon when they can spawn more than just zombies/spiders/skeletons:
The addition of "double dungeons" also makes it possible to find crazier things than in vanilla when they merge with other dungeons; for example, this is a double dungeon intersecting a normal dungeon for a total of 3 spawners:
Mining a monster spawner with Silk Touch drops an empty spawner block; the XP also still drops as this is a separate block:
An empty monster spawner after using a flint and steel on it:
Strongholds are also more exciting to explore as they have additional spawners in the libraries (silverfish) and under the chests in hallways:
In addition, what about a way to make maps of the caves you've explored? One way to do this is to only map areas lit up by player-placed torches (with structures using a different block); only areas that have been explored will show up, with higher caves overlapping caves deeper down:
(the following images show torches as yellow dots, which I've since removed from cave maps, as shown above)
Cave maps even work in the Nether, providing a way to map it; this also shows how they work in more detail, notice the single torch to the south of the player marker, which reveals the ground if the light level is at least 6 and there is a direct path to the torch within the range (walls will block it):
I even added a new tier of tools and armor, amethyst, which has many similarities to Netherite (slightly better than diamond, which was nerfed, somewhat like how 1.9 nerfed armor by adding armor penetration, though I just reduced the general protection, only for players though so amethyst is actually stronger than diamond in vanilla 1.6.4 when worn by mobs. Durability is triple that of diamond, even more for (vanilla) armor as I made armor have a similar durability as tools but repair costs are much higher) except it is found in the Overworld at 1/8 the rate of diamond in caves:
This is a chart I made of ore distribution; diamond and amethyst generate up to layer 8 instead of 15 since cave lava level (shaded red) was lowered to y=4, or the lowest 3 layers above bedrock at layer 0. The increase on layer 1 is to encourage players to branch-mine at a level they otherwise wouldn't (below lava level) and so I can find enough in a reasonable amount of time before I start caving (I only cave at the "end-game", branch-mining to collect resources before then):
Also, Mojang absolutely has to fix the following bugs before making a "cave update" (all of these have been fixed in TMCW; TMCWv5 will even use a true 64 bit RNG so every seed has unique cave generation, at least, as far as I can tell; in vanilla every seed is one of 65536 that are identical underground):
The "chunk seed" algorithm used by caves and some other features is quite broken (there are many issues here, ranging from the fact that certain seeds completely break cave generation (cause them to repeat at some interval) to the fact that most if not all seeds have identical caves at sign-reversed coordinate pairs, with 1/3 of all seeds having 1/3 of such pairs matching, which would become very obvious if uniquely large caves are added).
As a bonus, my custom 64 bit RNG is also far faster (7-8x) than Java's Random, so much in fact that by simply replacing Random with a functionally identical replica I more than halved cave generation time, one of the most time consuming parts of world generation; this and other optimizations also offset all of the increased complexity (it took less than 10 seconds to generate the map shown above, which is 16384 chunks, using a single thread; I used a separate mapping utility I made but it uses the same cave generation code as the game itself).
I also think that caves in oceans should NOT be flooded, which makes them not even "caves" in my opinion (as it is, I already prefer exploring under land and even modified world generation to make the area around the origin always land); I even made it so that floating sand/gravel are replaced with sandstone//cobblestone so they don't cave in (there are more water lakes and springs in ocean, as well as several other "wet" biomes like swamps):
Notice the ceiling at the top, which is below the seafloor, with patches of sand and gravel in dirt (I've since replaced stone with cobblestone so that underground gravel can't replace it and collapse):
I had an idea to use a monster spawner for battle arenas made of obsidian, but I'll need time to make this a reality someday.
This in my opinion would be the only "cheatless" way to farm them, as some other methods I've seen being used to farm mob spawners have been unbalanced and game breaking, involving the use of a half slab hole to hit them through so they couldn't fight back, that sort of exploit.
I don't want this being used in my current survival worlds so I've hypothesized a plan to make monster spawners more fun.
I've also thought of a design that involves a small piston activated drop hole to prevent the Creepers from wiping out the mob spawners, the obsidian shell would protect the spawners from the blast radius of the Creeper, focusing the danger against players in the arena.
Then gathering the loot from the monsters would be more satisfying, even better if I manage to find a double dungeon to use for it.
Ideally you'd want a zombie spawner and a skeleton spawner together, this way you get iron ingots and armour as well as bones and arrows.
I absolutely disagree w8th this; my entire playstyle hinges on the fact that you can travel across the world though interconnected caves underground, which is more or less its own dimension separate from the surface.
For example, this is an animation showing what I explored over about two weeks, all by moving from one cave system/mineshaft/ravine to the next underground; each play session (frame) represents over 3,000 ores mined and around 1,000 torches placed over an area of about 100 chunks (for scale, the newly explored area is about 1000 blocks north-south and the separate bit on the far left is a stronghold I found using eyes of ender, the only time I explore anything underground until the "end-game"; in the upper-right is the branch-mine I made to get resources before then, which is about 80x275 blocks):
This is also only a small part of the world, as shown prior to exploring the area shown above:
This is a close-up of the area to the east, showing things in more detail; the largest cave and ravine near the top-center have a combined volume of about half a million blocks, while the giant cave region to the upper-left has a volume of about 1.26 million (yet even that, the largest cave system I've ever explored in terms of volume, took less than 5 full play sessions to explore). The gray caves near the center are in a mesa biome (the mapping tool I used doens't recognize stained clay so it is uncolored):
For comparison, it is more or less impossible to do this in current versions; if you are lucky you might find a network up to around 1000 blocks long but the vast majority are much smaller since 1.7 made caves much more uniformly scattered instead of mostly clustered in dense cave systems (ironically, this does mean that 1.6 worlds have more cave-free areas between cave systems, but the individual caves in cave systems are much more interconnected):
1.6:
1.7:
You can also see that there is a greater local variation in cave density in 1.6, with some quite large cave systems near the middle (classic "1.6-type" cave systems) and a relatively cave-free region near the upper-right, while 1.7 shows little variation. Likewise, I've never had trouble making branch-mines below lava level as long as it is between cave systems due to the very few isolated caves that generate between them (maybe one reason Mojang changed caves is to reduce the size of these regions, then again, there isn't much benefit to mining below lava level in vanilla; I do this because of a very rare ore which is most common at y=1):
Also, one thing that makes the lack of customization of cave density/size/frequency quite ridiculous is how easy it is change - the only difference in the code between 1.6 and 1.7 is the change of two hard-coded numbers which control the size and frequency of cave systems:
// 1.6
int size = rand.nextInt(rand.nextInt(rand.nextInt(40) + 1) + 1);
if (rand.nextInt(15) != 0) size = 0;
// 1.7
int size = rand.nextInt(rand.nextInt(rand.nextInt(15) + 1) + 1);
if (rand.nextInt(7) != 0) size = 0;
In 1.6 the size ranges from 0-39, averaging 4.875, while in 1.7 it ranges from 0-14, averaging 1.75, or about 36% as large, but since this is a range this means the variation in size is also only 36% as high. The chance in 1.6 is 1 in 15 chunks while in 1.7 it is 1 in 7 chunks, offsetting much of the reduction in size (1.7 has about 77% as many caves and about 85% of the underground volume, the latter less affected due to less overlap between caves), and further reducing variation (the higher both numbers are the greater the variation is for the same overall cave density; worst-case would be a fixed size of 1 and a 1/3-1/4 chance per chunk, while a size of 80 and chance of 30 would have similar overall cave density as 1.6 but a much greater variation).
I feel like there isn't enough stuff underground to keep people going back after they no longer need to. I feel that they should make 1.17.0 the Cave Update. They should add mobs that only spawn underground to keep people going down there, even after they find a couple stacks of diamonds. They should also add more ores. Nothing better than diamond, but maybe something like rubies or amethysts to make it less painful and boring to find ores. Maybe they could even add something like a metal detector! It would tell you whether or not there are ores nearby. Maybe it would go in your offhand and it would put something extra in your HUD.
What do you guys think?
It needs to be huge.
That said, I would structure it around cave "biomes" with generated structures.
Biomes entrain themselves to the Overworld and generate designate the "base" block of the caves as well as the frequency with which given ores and structures spawn. These don't have to be a 100% thing either--for example, in deserts, there's a chance for the subterranean to either be primarily Sandstone or primarily Rock. So, your underground biome could be "Desert Sandstone Caves" or "Desert Rock Caves." This is already done to an extent, but it doesn't really affect much other than some ore weights and structures weights. Using this method, you could also introduce a variety of new "base" cave blocks, such as Limestone, Peridotite, Pumice (for some Overworld volcanic regions), Chalk, Marble, Jaspilite, or Slate, etc.
Then, with structures, introduce more "natural" structures into cave generation. Things like.... grottos, stalagmites and stalactites, some underground animal/plantlife (i.e. the mushroom grotto in the picture you include).
I agree that new ores (or more broadly, materials) should be added, but keep in mind they need a purpose. While aesthetic is a decent-enough reason to add a couple of items, a large-scale update like this would need some core functions. I don't dislike the idea of a Metal Detector, but perhaps that functionality could be tied to a Potion which is made with some new material found in the updated caves.
This would be a great opportunity to expand the sub terrain environment beyond Y 0 and move bedrock and the void further down. I figure if Mojang were to make cave systems and abandoned mineshafts and dungeons more interesting they first in my opinion should introduce something similar to cubic chunks in the vanilla game.
Instead of making ores more common and therefore making obtaining precious gemstones and materials too easy and unbalanced, they should instead make the underground section of Minecraft worlds thicker, yes there would be more ores to obtain, but you also put in extra work to obtain them. I say keep the ore rarity/common-ness or distribution the same as they are now, but with much deeper ground, perhaps with more lava the deeper you go to make it more hazardous and harder to obtain the diamonds, before mining the diamonds you first need to clear out the lava to stop ore drops being destroyed.
The new bedrock layer could be extended to Y -2048 to -2053.
It is Minecraft after all, and what better way to improve the game than focusing more of the gameplay design on the mining aspect? you want more iron? redstone? lapis? great, but then get back into the mining tunnels and get collecting and enjoy yourself.
Also with deeper ground environments this would be a good reason to add more ore types too.
I've pretty much made my own "cave update"; for one, I'd revert the changes made to the underground in 1.7, which made cave systems much less dense and much less varied in size (in 1.6 the "size" of a cave system varied from 1-39 but in 1.7+ it only ranges from 1-14), as well as mineshafts and dungeons much less common. However, I wouldn't entirely revert mineshafts; instead they generate using a system similar to structures like villages, where the game divides the world into 32x32 chunk regions with one village randomly located within each region, except mineshafts use a much smaller grid size, which prevents them from intersecting other mineshafts (they can even generate in adjacent chunks in vanilla) and whether one generates is dependent on the local cave density so they don't generate in areas of high cave density.
Caves would also vary a lot more, with regional variations in various generation parameters, such as the width of tunnels, size of rooms, how straight or curved tunnels are, tunnel length, and more. There would also be less common variants of caves and ravines that can become much larger, as well as cave systems with different cave variations, such as "ravine cave systems" made up of small ravines instead of tunnels/rooms, "circular room cave systems" made up of circular rooms (the round rooms you often find in caves), "maze cave systems" made up of caves which generate like mazes (multiple branches), and so on, even rare "colossal cave systems" base dona cave system in my first world (these are extremely rare in vanilla prior to 1.6; they would still be relatively uncommon but there would also be at least one within a reasonable distance of spawn) and even "giant cave regions" areas of many large caves intersecting to form a vast underground structure more akin to the Nether than a typical Overworld cave.
If all of this sounds highly specific, this is because this describes the underground of "TheMasterCaver's World", my alternative to updating to newer vanilla versions since 2014:
Here are more detailed maps (click to enlarge, the scale is 1 block per pixel or 2048x2048 blocks) of only special variants of caves and mineshafts/strongholds:
A small stronghold is visible near the lower-right (in TMCWv5 they will have a minimum size of 100 structure pieces, where most strongholds are above this). If mineshafts seem common here, they are actually only about 60% as common as in vanilla 1.6, but 50% more common than in 1.7 and later (their base generation chance is about the same as vanilla 1.6 but about 40% fail to generate as the local cave density is too high, or there is a large cave/ravine/special cave system nearby); they also a larger size variation than in vanilla:
These maps also do not show additional features being added in a future update, including enhancements to "underground biomes", where the underground takes on some of the characteristics of the surface, such as deserts having sandstone and sand in place of stone and dirt/gravel (currently this layer only extends down to around y=40, I plan to replace all stone down to bedrock, which is just one layer with cave lava level lowered to y=4 to make more use of the underground, and ores will have textures that match the blocks, e.g. sandstone-based textures in deserts):
A mesa mineshaft, similar to those in later vanilla versions, except the center room has red clay (a functionally identical variant of the gray clay found in vanilla); unlike vanilla, which simply adds more gold above y=32, extra gold only generates as part of surface mineshafts:
A cave in an Ice Hills biome (unique to TMCW), which replaces stone with packed ice and snow (the floors of caves have a mix of both, they can still be quite slippery):
This is the rest of the same cave shown above:
If that seems big, this cave has a volume of about 685,000 blocks, some 30 times larger than the largest single cave in vanilla:
This shows more underground decorations; there are more colors of mushrooms and variants of huge mushrooms; you can also see pockets of clay as this is in a swamp, which also have more water lakes and springs underground:
Yes, that's a stray near the center - I have no idea why they should only be able to spawn at the surface, making them totally pointless as I'd practically never see then, same for husks. Cave spiders and silverfish also naturally spawn below sea level (silverfish can only enter blocks if they came from infested blocks or spawners). You can also see that gravel can generate with both the vanilla texture as well as the old Beta texture (which I call "gravel sand" as it looks a lot like the sand texture, basically like much finer gravel), with the chance of each type varying on a regional scale (some areas have more normal gravel, others less. The 1.8 stone variants also vary in such a manner, so some areas mostly have granite while others have very little):
A ravine in a Mega Taiga; notice that the exposed dirt is podzol, the mineshaft is also made of spruce wood, which matches the type(s) of trees found, generally oak in biomes without trees (some biomes can have multiple types of wood, with any one mineshaft having one type):
A cave in a quartz desert (another biome unique to TMCW):
A cave in an Iceland biome:
Volcanic Wasteland, which reverses normal stone with andesite (pockets of normal stone generate in andesite) and adds pockets of magma blocks and greatly increases the number of lava lakes and springs with a complete lack of water outside of rivers. Ores are also more common in this biome, offset by the increase in lava and its rarity, and magma cubes spawn in place of slimes (slimes in general will spawn magma cubes if they die in lava):
A jungle cave, which is exclusively found under jungles:
Caves in jungles otherwise have more vegetation:
Caves in Mushroom Island have mycelium on the floor, as well as more mushrooms, including huge mushrooms in larger caves (they also generate elsewhere but much less commonly):
A ravine in a desert:
A ravine in Badlands (not the same as vanilla's "badlands" aka mesa biome):
A huge cave and ravine in a desert:
There are also more variants of husks to match the biome; in this case, red husks in a mesa biome:
This shows some of the many variants of ores, which use a transparent overlay that is overlaid on a base texture (I only had to make a single texture for each ore, which are overlaid at render time, similar to the side of grass blocks):
Likewise, these are all the variants of stalagmites and stalactites (note that I've since added a random offset, similar to tall grass, so they don't form such a regular pattern):
Also, there are an unlimited number of strongholds in the world, similar to Bedrock (but every one has a portal!) with one generating every 8192 chunks, and caves do not "cut" them apart (they don't in any case, in vanilla the walls do not overwrite air), which will also apply to mineshafts in the future (all parts, not just corridors):
Notice that the central room (the area with a dirt floor) and staircases generated planks below them (mineshafts in vanilla have been very buggy since 1.10 due to a poorly implemented way to prevent mineshafts from generating above the surface unless they are buried, which is applied to all mineshafts, my method instead checks the height of the surface and only affects mineshafts above sea level).
Dungeons are more varied, with most Overworld mobs able to spawn, as well as "double dungeons" which have 2 spawners, each spawning a different type of mob, and 2-3 chests. They are also much more of a challeng as they spawn mobs at a much faster rate, balanced out by the fact that there is a "cooldown" that disables item and XP drops if too many mobs spawn too quickly (preventing exploits, aka "mob farms"); spawners themselves are immune to creeper explosions (yes, there are creeper spawners) and can be mined with Silk Touch to obtain an "empty spawner" for decorative purposes (using a flint and steel on them will cause them to emit spawner particles and light):
You certainly never want to just run into a dungeon when they can spawn more than just zombies/spiders/skeletons:
The addition of "double dungeons" also makes it possible to find crazier things than in vanilla when they merge with other dungeons; for example, this is a double dungeon intersecting a normal dungeon for a total of 3 spawners:
Mining a monster spawner with Silk Touch drops an empty spawner block; the XP also still drops as this is a separate block:
An empty monster spawner after using a flint and steel on it:
Strongholds are also more exciting to explore as they have additional spawners in the libraries (silverfish) and under the chests in hallways:
In addition, what about a way to make maps of the caves you've explored? One way to do this is to only map areas lit up by player-placed torches (with structures using a different block); only areas that have been explored will show up, with higher caves overlapping caves deeper down:
(the following images show torches as yellow dots, which I've since removed from cave maps, as shown above)
Cave maps even work in the Nether, providing a way to map it; this also shows how they work in more detail, notice the single torch to the south of the player marker, which reveals the ground if the light level is at least 6 and there is a direct path to the torch within the range (walls will block it):
I even added a new tier of tools and armor, amethyst, which has many similarities to Netherite (slightly better than diamond, which was nerfed, somewhat like how 1.9 nerfed armor by adding armor penetration, though I just reduced the general protection, only for players though so amethyst is actually stronger than diamond in vanilla 1.6.4 when worn by mobs. Durability is triple that of diamond, even more for (vanilla) armor as I made armor have a similar durability as tools but repair costs are much higher) except it is found in the Overworld at 1/8 the rate of diamond in caves:
This is a chart I made of ore distribution; diamond and amethyst generate up to layer 8 instead of 15 since cave lava level (shaded red) was lowered to y=4, or the lowest 3 layers above bedrock at layer 0. The increase on layer 1 is to encourage players to branch-mine at a level they otherwise wouldn't (below lava level) and so I can find enough in a reasonable amount of time before I start caving (I only cave at the "end-game", branch-mining to collect resources before then):
Also, Mojang absolutely has to fix the following bugs before making a "cave update" (all of these have been fixed in TMCW; TMCWv5 will even use a true 64 bit RNG so every seed has unique cave generation, at least, as far as I can tell; in vanilla every seed is one of 65536 that are identical underground):
MC-7200 Cave/tunnel generation may cut tunnels a bit too soon (fix included) (the most insane thing is that this 7 year old bug report has a fix provided, which I implemented in the first version of TMCW, released 6 years ago)
MC-125033 Caves and ravines cut off unnaturally on chunk borders when near water (this is an absolute must-fix if giant caves and ravines are to be added; as with the above, I fixed it over 6 years ago by making them check for water on a per-block basis, if a bit odd-looking when a river hangs over a giant cave but I much prefer caves to be intact; for comparison, this is what vanilla does. Note that despite the "affects version" this has existed for as long as caves have, same for the other report)
The "chunk seed" algorithm used by caves and some other features is quite broken (there are many issues here, ranging from the fact that certain seeds completely break cave generation (cause them to repeat at some interval) to the fact that most if not all seeds have identical caves at sign-reversed coordinate pairs, with 1/3 of all seeds having 1/3 of such pairs matching, which would become very obvious if uniquely large caves are added).
As a bonus, my custom 64 bit RNG is also far faster (7-8x) than Java's Random, so much in fact that by simply replacing Random with a functionally identical replica I more than halved cave generation time, one of the most time consuming parts of world generation; this and other optimizations also offset all of the increased complexity (it took less than 10 seconds to generate the map shown above, which is 16384 chunks, using a single thread; I used a separate mapping utility I made but it uses the same cave generation code as the game itself).
I also think that caves in oceans should NOT be flooded, which makes them not even "caves" in my opinion (as it is, I already prefer exploring under land and even modified world generation to make the area around the origin always land); I even made it so that floating sand/gravel are replaced with sandstone//cobblestone so they don't cave in (there are more water lakes and springs in ocean, as well as several other "wet" biomes like swamps):
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?
I had an idea to use a monster spawner for battle arenas made of obsidian, but I'll need time to make this a reality someday.
This in my opinion would be the only "cheatless" way to farm them, as some other methods I've seen being used to farm mob spawners have been unbalanced and game breaking, involving the use of a half slab hole to hit them through so they couldn't fight back, that sort of exploit.
I don't want this being used in my current survival worlds so I've hypothesized a plan to make monster spawners more fun.
I've also thought of a design that involves a small piston activated drop hole to prevent the Creepers from wiping out the mob spawners, the obsidian shell would protect the spawners from the blast radius of the Creeper, focusing the danger against players in the arena.
Then gathering the loot from the monsters would be more satisfying, even better if I manage to find a double dungeon to use for it.
Ideally you'd want a zombie spawner and a skeleton spawner together, this way you get iron ingots and armour as well as bones and arrows.
@Agro thanks for PM
I like the original three ideas and also support biome changes. I think most urgent though is fixing the relevant glitches TMC mentioned.
I absolutely disagree w8th this; my entire playstyle hinges on the fact that you can travel across the world though interconnected caves underground, which is more or less its own dimension separate from the surface.
For example, this is an animation showing what I explored over about two weeks, all by moving from one cave system/mineshaft/ravine to the next underground; each play session (frame) represents over 3,000 ores mined and around 1,000 torches placed over an area of about 100 chunks (for scale, the newly explored area is about 1000 blocks north-south and the separate bit on the far left is a stronghold I found using eyes of ender, the only time I explore anything underground until the "end-game"; in the upper-right is the branch-mine I made to get resources before then, which is about 80x275 blocks):
This is also only a small part of the world, as shown prior to exploring the area shown above:
This is a close-up of the area to the east, showing things in more detail; the largest cave and ravine near the top-center have a combined volume of about half a million blocks, while the giant cave region to the upper-left has a volume of about 1.26 million (yet even that, the largest cave system I've ever explored in terms of volume, took less than 5 full play sessions to explore). The gray caves near the center are in a mesa biome (the mapping tool I used doens't recognize stained clay so it is uncolored):
For comparison, it is more or less impossible to do this in current versions; if you are lucky you might find a network up to around 1000 blocks long but the vast majority are much smaller since 1.7 made caves much more uniformly scattered instead of mostly clustered in dense cave systems (ironically, this does mean that 1.6 worlds have more cave-free areas between cave systems, but the individual caves in cave systems are much more interconnected):
1.7:
You can also see that there is a greater local variation in cave density in 1.6, with some quite large cave systems near the middle (classic "1.6-type" cave systems) and a relatively cave-free region near the upper-right, while 1.7 shows little variation. Likewise, I've never had trouble making branch-mines below lava level as long as it is between cave systems due to the very few isolated caves that generate between them (maybe one reason Mojang changed caves is to reduce the size of these regions, then again, there isn't much benefit to mining below lava level in vanilla; I do this because of a very rare ore which is most common at y=1):
Also, one thing that makes the lack of customization of cave density/size/frequency quite ridiculous is how easy it is change - the only difference in the code between 1.6 and 1.7 is the change of two hard-coded numbers which control the size and frequency of cave systems:
In 1.6 the size ranges from 0-39, averaging 4.875, while in 1.7 it ranges from 0-14, averaging 1.75, or about 36% as large, but since this is a range this means the variation in size is also only 36% as high. The chance in 1.6 is 1 in 15 chunks while in 1.7 it is 1 in 7 chunks, offsetting much of the reduction in size (1.7 has about 77% as many caves and about 85% of the underground volume, the latter less affected due to less overlap between caves), and further reducing variation (the higher both numbers are the greater the variation is for the same overall cave density; worst-case would be a fixed size of 1 and a 1/3-1/4 chance per chunk, while a size of 80 and chance of 30 would have similar overall cave density as 1.6 but a much greater variation).
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?