Decoration layer doesn't regenerate correctly [1.16.1 beta 2]

Versions

WorldEdit version: 7.2.0-beta-02+d10d7d6
Platform version: Bukkit

Describe the bug

When running //regen the decoration layer doesn't regenerate correctly.

To Reproduce

1. Select an area with trees/grass/etc. (Basically any area works since most areas will have things generated in the decoration stage)
2. run //regen
3. The trees/grass/flowers/etc. are now different.

Expected behaviour

The decoration layer doesn't change when regenerating.

https://gfycat.com/SlipperyGroundedAmericancurl

Thanks for that, I didn't have time to upload any images/videos when I made the issue.

thanks for what? this is a counterpoint to your bug report.
as mentioned in discord, it works fine for us so it's on you to somehow show it doesn't work.

That video shows it working fine

I'm sorry, but your video was showing the bug in action...

The //regen command should've regenerated the tree and not deleted it.

It did regenerate the tree?

I used //set 0 to delete part of the tree and then //regen to show that it pops back up exactly as it was...

Wait, am stupid and only watched first part of the gif.

I'll get some pictures of it now and possibly upload some videos later.

Before regen:

After regen:

Before regen:

After regen:

From the minimal amount of testing I did before, it was working on everything, but then again, I only did it on 1 area.

What Minecraft version was the world generated in

moreover, do multiple invocations of regen on the same area produce the same results? or are you only comparing to what you believe to be the original world gen.

I'm pretty sure the world was generated in 1.16, but this also happens in 1.16 only terrain. (I'll attach more images in a second.)

more images don't really help tbh.

New nether terrain:
Before:

After:

The only "guarantee" that regen makes is that it'll replace the terrain with what the world generator says should go there.

It being so similar to what was there prior makes me think this is a slight change in the generation algorithm potentially made by Spigot/etc. The only place we could be doing something wrong is passing in the wrong seed, but that would produce vastly different results.

Fair point.

Though when I was doing some code digging in world edit, it seems you just copy the same world generator as the current world, so I'm not sure why it does this.

From what I understand about seeds, some things like the decoration generation use more bits of the seeds than things like the terrain generation, so it could be something where the upper bits of the seed are off by something, but not the lower ones. /shrug

I'll close the issue now if you want, as nothing major like structures are being changed.

Generally seeds are setup in a way that a tiny change produces massive changes, so the upper bits being off would definitely not produce results like this unless there was some ridiculously unlikely coincidence

I was doing some research a while ago about brute-forcing seeds and how some things can only be used to calculate some of the lower bits of the seed. Like how the obsidian end pillars can be used to calculate something like the lower 8 bits, but I digress.