Updating the world causes some loaded unchanged chunks to regenerate incorrectly

The same problem ((((
This broke my world in the realm where we had been playing with my children for a year and a half 😢

Still a huge Problem :(

I can confirm (I accidentally made a duplicate) but to clarify, the chunks that regenerate incorrectly are the ones that the game never saved. From my experience, it seems like the game thinks that the old loaded chunks are frozen plains and try to blend them in with the iceberg biome.

FIX (maybe)

One fix for this, if you have a backup from before reloading the area, is to use https://www.chunker.app/ to update the world version, the conversion process make it so the game thinks the old loaded chunks are from the current version so it doesn’t try to incorrectly blend them in (my theory). It also works if the backup was opened in the newer version but the problematic area wasn’t visited (in this case, you just force the update of the chunks with the tool before the game does). Unfortunately, it might also break a necessary blend somewhere else (where there would be a new biome) if you can’t load that area before but I cannot verify that (my biomes haven’t changed in the loaded part of my world).

It worked for me:

After that, you should probably make sure to load ALL the chunks of the area before the next update.

Its an interesting idea. But how can I do this for realm?
I don't worry so much about other worlds. Only about the world in the realm where I've been playing with my kids for a long time. And it's terrible what happened there with the frozen oceans :(((

This affects trees too and isn’t limited to cold biomes, as shown by these before and after map screenshots.

Same here my world is also affected with that bug and i'm on version 1.21.82

This is a really horrible bug that really needs to be fixed. And it should be pretty trivial to fix based off of what Loic discovered.

Loïc: thank you for the information. Are you saying that when the game generates chunks and checks whether neighboring chunks have been generated in a previous version, it then fails to compute the biome correctly for the chunk it is generating? Or is it failing to read the biome data of the previously saved chunk, so that the blending in the new chunk assumes a default biome for the (seed-computed) temperature?

Note: this sounds like the same underlying mechanism as MCPE-175332.

No, what Loic is saying is that, if when the game updates to a new version, minecraft were to mark all chunks as generated in the new version before loading the game, this problem may go away. That would be a pretty trivial fix.

The desert is also affected with that bug and the game things desert is lush biome

Having similar issues and it’s incredibly frustrating, is there any way to fix it yet?

Nope, it sucks and I don’t think they’ll be fixing it anytime soon. This has been an issue for a while I feel like.

GoldenHelmet: I am saying that when the game generates chunks and checks whether neighboring chunks have been generated in a previous version, it then misinterprets the biome data of the previously saved chunk (or fails and assume a default). Then, there is a wrong blending in the new chunk causing the discontinuities.

And no, it doesn’t seems to be exactly the same underlying mechanism as MCPE-175332 since it seems to be missing the blending (the biomes seems to be unchanged in the screenshots) rather than blending with the wrong biome.

Also, I don’t really agree with the description of this bug and I opened MCPE-217769 which was closed as a duplicate. Sorry for the delayed response, I hadn’t enabled the notifications.

et1et got the idea of the way I fixed the issue for my world. It only works since the biomes in that area of the world didn’t change between the versions.

blab blob: Have you read my previous comment? It has the description of my fix.

P.S. THE BUG ISN’T FIXED YET! (opening the game with my backups still cause the bug). I would still like to see this bug fixed so I can enjoy opening my old backups again. Here is one of them if it can help (1.21.5* according to https://www.chunker.app/ ):

Still a problem in 1.21.100

The bug it's still active on 1.21.100 and only happen when you update minecraft

Isnt it fixed in the latest Preview?

No only Rivers were partely fixed, Frozen Oceans are still broken

Still active on 1.21.101

As said it is still around as of the latest version. It produces a different issue with stone with the recent changes, making terrain look even more like a wasteland than before

Just make it work like Java already. Can’t be that hard, since they have chunk blending without problems at this point for years… Older worlds are pretty much unplayable at the moment, especially of you're in a cold biome, but not only there, weird chunk borders and the world looking completely different after every update ist a universal problem… Chunks should not be blended together, if there isn’t a major terrain overhaul

If that isn’t possible, revert Chunk blending to it's first iteration, since it wasn’t really that buggy at that time (1.18.0)

The Cliffs from the first iteration were also kinda stylish, compared to now, where Cliffs and Mountains from the world gen just get flattened

The surrounding Blocks were also used, instead of Thomas from the corresponding Biome, which can now lead to ugly borders, because of updates for biomes

*the surrounding Blocks were also used for Blending, instead of using the Vegetation from the corresponding Biome,…

(Autocorrection messed Up)

As mentioned by Graylen_MYT25, the bug is still around (after all this time) BUT IT'S WORSE! The bug now seems to affect worlds from after the 1.21.51 update (I have a backup in 1.21.7x). The iceberg biome changed (so all version before the new change might be affected) which means that the trick I used to fix my world is no longer a solution. The only solution now is probably to load the world in a previous Minecraft version (good luck with that), load all the chunks (which is not fun) and update Minecraft.

Minecraft version : 1.21.101