Nehtdx

I have an existing Minecraft world, on a shared server, that has been running for several years now. I'm looking for feedback from anyone who has updated an existing world to 1.13. (Finding this info is surprisingly difficult!) Specifically: What breaks? What doesn't? And how do ocean changes affect the world?

The only info I can gather seems to suggest that highly customized commands may break (we don't have any, so should not be an issue), that many plugins will break (we aren't using any), and that areas that have been explored won't generate new structures such as wrecks. It's the last bit that I am trying to verify: No new structures, but will new aquatic plants spawn? I'm envisioning our world with empty, barren oceans until we travel huge distances from home (we've explored a very large area...)

Asking with full understanding that 1.13 final is not yet released - looking for feedback from anyone who has used the prerelease versions on an existing map.

Pretty much all commands break, since the entire command system was overhauled. With some automatic converters you can upgrade them or alternatively replace them manually with better solutions that are new in 1.13. Most changes can be found here, but that post was made before the changes were done and there are some additional changes. But the new autocomplete is very good and mostly explains itself and the wiki was over time also updated, it should be accurate again now.

The data pack structure has changed and of course texture packs also have to be updated to include the new blocks, entities, etc.

Customised worlds don't work in 1.13. They can't be created, but they can be opened. When opened in 1.13, any new chunks generate like in a default world. The "buffet" world type replaces customised worlds, but it's neither completely done yet, nor does it have all features of customised worlds in 1.12. It's planned that they return later, but there's currenty no date or version known for that.

There are a few other world generation changes, they might cause a few visible chunk borders, but nothing major.

Mob systems that drown zombies to kill them don't work anymore, because they are converted into "Drowned" now.

All undead mobs sink in water.

Baby zombies burn in daylight.

You'll have to either wall yourself in or have a solid block above you for AFK farms now, Phantoms spawn when you haven't slept for at least 3 nights in a row. They fly, but unlike vexes and dragons, they don't fly through blocks. Having a solid block above you prevents them from spawning.

Water physics have changed a lot. In theory they shouldn't break existing builds, but there might still be some bugs with edge cases left.

Items and XP orbs float up in water.

Beds break if they have no supporting blocks under them. Since they were non-functional without support before anyway, this should only affect decorative beds.

TNT that explodes when mined was removed and turned into regular TNT in 1.13.0 and readded in 1.13.1. If you skip 1.13.0, they should upgrade properly.

And most importantly: Because there was a deadline for 1.13, it was developed pretty hastily and there were still many bugs, some quite game-breaking. There's also a lot of lag, both fps and tps lag.

In general I would not recommend updating to 1.13 at all. Instead, you should stay in 1.12.2 or, if you want the new features, directly update to the latest 1.14 snapshot.

Usually, snapshots are unstable, buggy, laggy etc., but since 1.13 was in such a bad state, the current snapshots are actually more stable than all 1.13 releases.

Keep in mind that snapshots are development versions. The 1.14 snapshots currently still have some quite severe bugs, even if they aren't as bad and as numerous as in 1.13. For a stable game, you should still stay in 1.12.2.

Of course 1.14 has additional changes, the main ones that impact an existing world are these:

Some commands, datapack, resource pack and similar related things have changed again, but not as drastically as with 1.13.

Sticks are dropped by leaves sometimes, so if your tree farm assumes that you only get saplings and wood, you should consider that.

Dispensers can now shear sheep with shears. I don't really expect this to break anything, but it could in theory.

Ocelots no longer turn into cats when tamed. Instead, cats are their own mob.

Combining tools, weapons and armour in the crafting table no longer works, this task was moved to the new "grindstone" block. Of course you can still use the anvil.

Vindicators can break doors.

The textures were updated to the new pack that was available for a while already. The old textures are available in the resource pack menu.

Lapislazuli, cocoa beans, bone meal and ink saks now have to be crafted into dyes before they can be used as such.

In both 1.13 and 1.14, there were a few changes in world generation (mostly oceans in 1.13 and villages in 1.14), so in some places you might see borders between old and new chunks.

I would like to say a little more to the wolrd generation, as that was touched by the other answers only briefly (and as a singleplayer explorer/builder is usually my main concern).

First of all, as you seem to know already yourself, no, the new ocean features (neither wrecks/ruins nor any kind of new vegetation), will not appear in already explored parts of the world. They will only be generating in newly generated chunks. The existing ocean biomes will also stay normal ocean biomes, which means they will likely not spawn the new mob versions of pufferfish, tropical fish and salmon either, since they're supposedly spawning in lukewarm/warm and cold/frozen oceans respectively (salmon will spawn in old river biomes, though). And I doubt this will be changed, since I haven't read anything to this effect so far and I imagine just adding seagrass/kelp/coral into already existing chunks would be extremely complicated without properly knowing which regions are natural and which have been player-altered.

The good news is, the raw terrain hightfield generation as well as the biome layout has stayed the same, so there won't be major chunk borders between old and newly generated parts of the outside world. However, the generation of decorations seems to have changed to some degree, so the placement of trees and lakes and things like that might be a little different.

But together with other decorations comes a major thing that I haven't really seen adressed too much in discussions yet. The entire cave generation has completely changed. Caves, ravines and mineshafts are completely different (likely in order to incorporate the new underwater cave generation). Now how disruptive these changes are depends on how you use and explore the naturally generated caves. Fortunately, due to natural caves themselves seeming rather chaotic in general and rarely observable in a bigger picture, the chunk discontinuities might not be all too noticable. But be aware that this also extends to places where caves meet the overworld, most notably ravines.

_{I can't say too much about the nether as I haven't given it much testing yet. What I observed from a few short glimpses is that, while there are supposedly new natural ravine structures in the nether, the overall rough world layout and cave system seems to be the same still. The generated nether fortresses, while at the same place, seem to generate a little differently, though. But as said, I can admittedly only speculate about the nether.}

Just in case anyone else has the same question: In testing, I made a test copy of my world, then in the copy, used MCEdit Unified to select areas away from all bases, then set these unprotected chunks to repopulate. I am only selecting chunks with water, leaving most land biomes unchanged (selecting ocean, beach, and river). This left built-up areas unchanged but did spawn new biomes in all repopulated chunks, including ocean ravines, ruins, and shipwrecks. I didn't expect "repopulate" to actually regenerate terrain, but it did - quite noticeably showing the difference between 1.13 and prior versions near our main base, as a chunk adjacent to a protected section went from ocean to island. Have not done this to the live server world yet, working on the test copy only, with intent to copy to the server when 1.13 is stable in Spigot. (Will obviously keep an unaltered backup just in case!)

Testing showed that villages selected to repopulate respawned as expected, as did jungle temples. A newly created 1.13 world using the same seed as my original world generated shipwrecks and ruins in the same locations as in the repopulated chunks of my test copy, so (as with prior structures) these are not randomly placed. And replanting kelp/seeding ocean grass is a bit tedious but can be used to mask hard transitions between repopulated and "original" areas. Last, while Nether and End were not affected (as expected), Nether portals to repopulated chunks did work, creating a new above-ground portal in the newly-generated territory. Most areas were recognizable as the same from the original world, with mostly minor differences in terrain and shoreline.

If taking this approach be aware that any blocks previously placed or mined are reset when the chunk repopulates. For extensive mines you wish to save, you'll need to ensure that protected chunks include the underground areas you want to keep. This can result in some pretty big "empty" areas of ocean above.

If you aren't that worried about large areas, it might be way faster to simply prune those chunks rather than hand-editing the water-only bits. There is an MCEdit script floating around Reddit that automates the process by deleting all water or beach chunks, but I was too concerned about very specific (and widely scattered) shoreline bases to trust the full-auto approach. A bit surprised to see that repopulating and deleting were in effect doing the exact same thing - unclear if this is expected or not; perhaps the 1.13 update conversion process treats unpopulated chunks as if they need to be fully created from scratch.

End result: The important parts of the world are safe, the lightly explored or all-water areas are updated, and fancy new ocean features abound. I expect to see occasional awkward transitions due to the change in terrain calculations but I can live with it!