Substitute Chunk Generation

[Zetal]

Hello there! As a bit of a fun little project, I've been working on a mod that will 'loop' a Minecraft world within a configurable rectangular area, by chunk. While I have the events in place to teleport a player to the other end of the world when they reach the 'edge', I was hoping to also be able to substitute the chunks beyond the border with the chunks on the other side of the world, making the teleport as seamless as possible (since the chunks that the player is walking into are, after all, already loaded ). 

 

However, I see in the documentation that the ChunkEvent.Load event is NOT cancellable. I was wondering if anyone knew a good work-around for this? Thank you!

[jabelar]

Well, the event does pass the actual chunk, so I suppose you might be able to manipulate it directly. For example, maybe you can assign it to a "shallow clone" of the chunk it is supposed to be looped from. A shallow clone means that the Chunk itself is a separate instance but all the fields point to the same memory as the fields in the other. People that know more about advanced Java than me can probably advise on whether this is viable, but it is the first thing I would try because then things like entities and blocks would not need any additional synchronization.

 

If that didn't work, then I would try a deep copy -- meaning actually copy every block and entity and such into the chunk. I'm not sure the most efficient way to do this,  but I know chunk generators uses a ChunkPrimer to do the placement then convert that to a chunk. You'd need to figure out the best way to keep them synchronized though, especially if there are entities and such involved.

 

If that didn't work, then I would try replacing the whole chunk generator with one that repeats. Again you'd need to think about how to keep the looped chunks synced up in terms of any changes and entities.

 

All the above are assuming creating an actual chunk is needed. It may be possible though that you can get the effect just by doing rendering. I'm not sure but it actually might be simple to make a modified world renderer that gets the data from looped chunk data. The only only trick would be that technically there would be chunks being loaded that are not being rendered and so you'd have to protect against things like entities wandering from those chunks into the rendered ones, and such.

Edited January 25, 2018 by jabelar

[Zetal]

Hi! Thanks for the advice  I tried the first method, as best as I could anyway, by using Reflection to loop through all of the fields in the 'replacement chunk' and set the equivalent fields appropriately, but unfortunately a lot of the fields inside of the Chunk class are 'final'. I can use Reflection to ignore that modifier, but the JVM won't recognize the values as having changed.

 

I'm beginning to think perhaps this is a bit more complicated than a quick and easy fun project would suggest...

[Draco18s]

You need to use Reflection again to remove the final modifier.

https://stackoverflow.com/a/3301720/1663383

[Zetal]

Quote

I can use Reflection to ignore that modifier, but the JVM won't recognize the values as having changed.

 

I did indeed do that, Draco- unfortunately (as the caveat in that exact answer you linked points out) primitive types that are final are not properly updated via reflection. I'm assuming this is why my implementation doesn't work, but I could be mistaken. Perhaps there is some other behind-the-scenes shenanigans causing it?

[jabelar]

You need to carefully choose the type of "clone" or copy you are doing. You can always replace the chunk passed into the event with a new chunk, rather than trying to selectively replacing fields within the chunk. But make sure you understand the difference between deep and shallow cloning. You may need to do a "deep" clone.