Coordinate math error causes structure not to generate and possibly other issues

Here is the exact change.

The 1.12 code is:

if (chunkX < 0) {
  chunkX -= this.maxDistanceBetweenScatteredFeatures - 1;
}

if (chunkZ < 0) {
  chunkZ -= this.maxDistanceBetweenScatteredFeatures - 1;
}
int k = chunkX / this.maxDistanceBetweenScatteredFeatures;
int j = chunkZ / this.maxDistanceBetweenScatteredFeatures;

The 1.13 code is (ignoring some irrelevant differences in where the constants come from):

chunkX = chunkX < 0 ? chunkX - maxDistanceBetweenScatteredFeatures - 1 : chunkX;
chunkZ = chunkZ < 0 ? chunkZ - maxDistanceBetweenScatteredFeatures - 1 : chunkZ;
int k = chunkX / maxDistanceBetweenScatteredFeatures;
int j = chunkZ / maxDistanceBetweenScatteredFeatures;

Subtle!

Put another way:

chunkX -= this.maxDistanceBetweenScatteredFeatures - 1;

is the equivalent of:

chunkX = chunkX < 0 ? chunkX - (maxDistanceBetweenScatteredFeatures - 1) : chunkX;

which when simplified is:

chunkX = chunkX < 0 ? chunkX - maxDistanceBetweenScatteredFeatures + 1 : chunkX;

Really good catch and very subtle error.

This bug was reintroduced in 1.13-pre7.

I was already wondering why some shipwrecks and ocean ruins I knew from older snapshots seemed to be gone lately. I hope this severe world generation problem doesn't get forgotten before we get 1.13 and people all around the globe start new worlds with no updates around for months.

I implore Mojang to consider that a working world generator is essential, especially since it just got a major overhaul and many people will restart at least parts of their world. When a chunk is generated, you can't repair it anymore. Having this working in the proper release and not be touched for a significant amount of time is more important than keeping exactly to some arbitrarily chosen release date.

Yes, unless coordinates for the new structures are handled separately, shipwrecks and ocean ruins would be impacted more greatly because of their smaller region size. There would be ~25% fewer shipwrecks and ocean ruins overall (and all the missing ones would be in negative X or Z coordinates).

This is a nasty regression. Thanks for catching it up. It is now fixed again.

I apologize for not noticing until literally the last minute.

The question is when 1.13.1 is scheduled for, seeing how this is a major world generation fix preferable to be out as soon as possible.

Yes this correct. I can confirm this is the case. i too am getting this problem in my world. far less dungeons are being generated and this is also the case for guardian temples.

I am using the 1.13 release and when i look at the 1.12.2 for every 1 dungeons in 1.13 there is 4 in 1.12.2 this from me looking at my seed and writing down the locations then flying to those chunks and looking around

It's already fixed. Confirm for 18w30a when it is released.

thanks Matthew For info 🙂 Please were can i see the problems that have been fixed with the next roll out and the date we can expect them.

Again many thanks for replying so quickly.

Right now. It just came out right now!

@simon - This bug does not affect dungeons or strongholds at all.

It has a relatively small effect on guardian temples (maybe 1.5% are missing compared with ~25% of shipwrecks and ocean ruins, and about ~8% of villages, witch huts, etc).

1.13 naturally has a lot fewer guardian temples than 1.12 because of the changes in ocean generation. They require deep ocean (any kind of deep ocean) and there is less deep ocean now. There is no such thing as warm deep ocean, so you'll get shallow warm ocean where you might have gotten deep ocean before. Also there is less deep ocean near shorelines for somewhat complicated reasons. So fewer guardian temples is mostly WAI.

Hmm, the ocean ruins I missed seem to be back, but the two shipwrecks I lost are still gone. I guess they just changed the shipwreck algorithm in some previous snapshot.

I've verified that this is fixed in 18w30a.

It hasn't fixed /locate

1. MC-108801