Block ids are inserted wrongly into chunk section block palettes

at some point i got confused about what version I was using so I edited that out.

Also affects 18w07b and 18w07a.

Couldn't find even a single chunk of missing leaves/trees, or a full chunk section of leaves. Can you two please force a crash by pressing F3 C for 10 seconds while in-game and attach the crash report ([minecraft/crash-reports/crash-<DATE>-client.txt|http://hopper.minecraft.net/help/guides/finding-minecraft-data-folder]) here?

edit: did you maybe restart the game while one of the chunks was generating?

Sure. But also like I said the best way to re-create it is to generate a random new world and look around for it.
If you load the seed or re-create the world you wont find the same error generated in the same places or even at all.

edit: No I didn't I looked around some worlds for a good solid 10-20 minutes sometimes before finding a missing gap or giant chunk of leaves.

To me it looks like a sudden math error with tree and forest generation as the game attempts to properly load that chunk and it either dumps a bunch of blocks in that its supposed to or none at all; and then if you remake the world it doesn't always meet that generation math error and it can generate as it is supposed to.

Okay I do not get it why this post isn't made duplicate because mc125073 is far before this one so that one should be reopened

weird mushrooms in 18w08b
Regenerates normally as it is supposed to if you remake the world just like the other chunk errors above.
Included in the screenie is the seed
but for formality here is the seed in text form for easy copy pasting. 8869563041474427484

If you have an affected world please zip it and upload it.

I have successfully reproduced the bug in a Superflat world.

Instructions:
1. Create a new Superflat world.
2. Use the Overworld preset. Change the biome ID from 1 to 29 (Roofed Forest).
3. Use a seed of 1. (Any seed can probably be used but this is the seed I chose).
4. Use Creative mode.
5. Create the world.
6. Fly around the world for a while generating new chunks. Eventually you'll see one of these odd chunks. I found a Wood chunk within 30 seconds and then a Leaf chunk. (I also found a Desert temple at 234, y, 169 which is another bug).

I've been searching for ~10 minutes and haven't found any following those steps (and on 18w09a). Can you give me the coordinates where some of those chunks appeared?

I used the 18w09a snapshot. I had some difficulty recreating the issue from a fresh instance of MC. I originally reproduced it after creating about four worlds in the same MC session, one after the other (all with the same seed but different kinds of worlds: Default, superflat plains (with "biome-1" altered to an invalid "biome_29" setting), superflat roofed forest). The last one had the strange wood and leaf structures.

Hm. Still not happening for me, unfortunately. Can attach the world (or at least the region file containing the effected chunks) to this report?

When looking at the world we do have access to, I found that the chunk section with messed up leaves had a palette with 32 (2⁵) entries. But when regenerating the world, it instead had 34 entries. I'd like to check if a similar thing happened.

I did see some of the weird cut off trees. However, I'm not entirely sure that that's the same issue (it feels different to me; probably it's a bug in the tree generator)

I have attached a file called "TestRoofedForest.zip" that exhibits the issue. Two points of interest are at 216 80 136 (leaf blocks) and 151 80 -72 (wood blocks).

I generated a new one on 18w09a

I'll include this world
its called 18w09a 1 because thats the first world I generated on this version

this is only the 2nd time I have come across the wood blocks like this

Simply face south when you spawn and fly up can't miss it.
Coordinates to the broken chunk 186/ 82/ 137
Seed: 7908767748096905097

Please create a new ticket for your floating tree.

@@unknown: In your original description, you said that breaking blocks manually makes them disappear visually, but you can't walk into their space, and that they come back when you reload the world. Does this only happen the first time the world is loaded, ie directly after the chunk is generated, or also after reloading the world? I tried to reproduce this behavior using one of the world saves attached here but I can break and replace blocks and the changes are permanent.

Sorry for the update spam, everybody.

It is rather inconsistent on how the blocks behave when it generates like this.
For the first giant wood block i found I broke a full row of blocks along the side and then tried to stand where the blocks were and then I couldn't, there were ghost blocks in the way.

When I re-load the world and break blocks there were no ghost, but previous blocks broken when there are ghost blocks get replaced as normal as if nothing happend to the block. You can break more blocks and they stay broken, but if I find a new chunk of blocks there will be new ghost blocks if you break any if the games natural decay doesnt take the blocks.

I would upload my world, but your limit is 10.00MB while the world is like 22.90MB. D:

Hope this glitch AND the elytra glitch gets fixed real soon or Minecraft won't be fun! :|

@unknown Could you provide your seed? If you want to upload your world, I would recommend doing so by using a file uploader and then just posting the link here.

Well i can tell you the seed.

-8794717663863046517 but it didn't appear again

If you are wondering where i found it, 1. Fly up, 2. Look for Swamp, 3. you find it.

Im uploading it to Google Drive right now.

https://drive.google.com/file/d/1ll2P3sKSugqINKDPZGRsyLVJaiyBbCs3/view?usp=sharing

@unknown, thank you, I've added your example to the description.

If you want to have more screenshots for the problem, you can watch for my ask which is the last in the duplicate ones. That can possibly help the developers to fix the bug.

World download for the Kelp that turned into Coal Ore.

Download

@@unknown: Thanks, but the download link is private currently.

Sorry about that, it should work now.

Confirmed for 18w22c

This bug also affects the 1.13 pre-release

I have taken a look at two affected chunk sections and found they have some common features.

It helps to understand how 1.13 saves chunk data. Chunk data are saved in Sections. These Sections store the blocks in a Palette which describes the blocks, and index into the Palette with an array of Long called BlockStates that can vary in size with a minimum size of 256 (corresponding to a Palette size of 16). These sections also have other data.

In chunks with this corruption, the Palette appears normal. The BlockStates array is corrupted. The BlockStates array has many repeats of the value "1". Sometimes this fills the entire BlockStates array, other times other values are present but the value "1" dominates.

In a corrupted BlockStates array I examined with 27 entries in the Palette, the first two Longs look like this:

{color:red}21{color} 84 10 42 08 21 84 10
42 08 21 84 10 42 08 21

To decode this, reverse the hex values (little endian order), convert to binary and take five bits at a time:
10 84 21 08 42 10 84 {color:red}21{color} ...
(8 values) 0100 0010 0001 0000 1000 0100 0010 0001

...01 00001 00001 00001 00001 00001 00001
...-- ----- ----- ----- ----- ----- 00001 = 00001
...-- ----- ----- ----- ----- 00001 ----- = 00001
...-- ----- ----- ----- 00001 ----- ----- = 00001
etc.

The whole array has repeats of the sequence 21 84 10 42 08 which means it is filled with the value 00001.

The other array I examined had other values as well but the value 1 dominated.

It looks like the value "1" is used to initialise the array and then the array is populated with the correct values. It looks like the population of the array occasionally terminates before completion leading to the corruption.

Confirmed on 1.13-pre3, seed -4270258239336733475, chunk -21, 6, -12

This should be fixed by using the default JRE that's available in the newest launcher update.