Colton Dever

This is normal

Why are you using a 1.17 snapshot? You should upgrade to the full release 1.17.1 before trying to go to 1.18 pre release...

Bummer, looks like you're right.

Note: I will add a world download once I have it uploaded to a hosting site.

Added pre release 6 screenshots in brand new copy of seed. Mostly fixed but still looks very strange. Water seems to just be coming from mid air with no blocks under or on top of it.

Won't be fixed? Seems like a pretty big mistake on Mojang's part, especially when they chose to use the original taiga (with snow) id in 1.7 as the default taiga, and gave the new snowy taiga a new id. It would make more sense for those old taigas to get the new ID when upgrading from 1.6.

Yes, correct. The sand should be considered when blending an old sand floor with a new one.

Not a new world, but freshly generated terrain inside an old world.

Added more information.

I see this was marked as resolved. Would a zip of my affected world still be helpful?

I thought of that too, but this also happens when you've updated your 1.6 world to 1.17. My single player world is one of these instances. The chunks have already been upgraded to 1.7+ 'taiga'. It would be a very small amount of people going from 1.6 straight to 1.18, and any world that has these old biomes that's been played in since 2013 would be affected using that solution. Unfortunately checking region files for creation date will not work either, since if you move your world from its original file location whatsoever, that data is lost and replaced with the move date. So for example since I have gotten a new PC since 2013 when I created those chunks, the creation date wouldn't be accurate.

There really needs to be a 'snow_layer' flag or something that the world generator can check for. It already sort of exists, since grass with snow on top is already identifiable. Maybe just check if the grass has a snow layer, and if it does, continue the snow into a smooth transition like any other snow biome from 1.7+.

That would fix the issue, yes. However, in 1.7, the biome kept its "taiga" id, and since it wasn't converted to "cold taiga" (like it should have been), there's no way for the game to check if it's the snowy variant, besides checking if it has a snow/ice layer. The game sees these 1.6.4 snow taigas as the exact same thing as the 1.7+ plain taiga. It rains there, ice does not freeze, etc. This is why I'm suggesting that when blending, the world generator checks if there's a snow/ice layer on the ground/trees, and if so, it generates 1.7+ snowy taiga that will visually match the 1.6.4 and lower "taiga". This won't solve the rain in old taigas, but that's something that's been happening since 2013, so probably not going to be changed, and it probably can't easily be changed now anyway.

Attached is a screenshot of the zipped world, upgraded to 1.18 pre 5. The actual land formation does blend pretty well, but you can clearly see this issue with the snow/temperature not blending. I believe this issue is due to the temperature of the 1.7+ taiga biome being too high for it to be icy (you can see where the frozen river and frozen ocean edges cut off sharply) but it also clearly happens with the snow layer placed on top of the taiga biome when it generates.

Note: Trying this in the same world, but in pre release 4, the chunks generate and it does not crash.

It is re-producible on any 1.6.4 taiga biome but sure, here's an example. if you open this world in 1.18, it will blend the biome but not the snow layer.

Note: The zip file here is not my exact world, only an example/test world, however the behavior/conditions are exactly the same: A 1.6 generated taiga biome that new terrain is generated on the border of the 1.6 generated chunks.

I also tested upgrading a 1.6.4 world directly to 1.18 pre 5 and this was the result. The left/top is 1.6.4 terrain, the bottom/right is 1.18 pre 5 terrain.

I did. I have been updating every snapshot since I think 21w39a with this world. I skipped 21w44a due to some bugs I didn’t want to deal with with the bedrock not generating, so this world came from 21w43a—>1.18pre1

I also have this issue and have reported it as a bug. Ampolive has also commented on my issue that it’s a duplicate with the issue they linked. It  is a separate issue from the one they keep linking. Ampolive please stop linking that issue. 

This is not a duplicate issue with that linked issue. Completely different.