Okay so you know how you have chunks and they map to 4 levels of biomes?
Logically you'd go hmmmm, let's just map 4 Y levels to one biome level.
Except there aren't 16 chunk heights, there are about 17 if you count
Y=16 (which can contain data), but there's also -1 technically but I've
never seen this have data in an NBT structure I don't think.
Anyway, let's just hope we're doing the right thing by giving Y=16 the
same biome as Y=15. If someone wants to check whether that is actually
correct please feel free to, but for now it's better than crashing at
the very least.
Would be nice if we had a spec for these kinds of things.
Fixes#1685.
Apparently rotated worlds would try to access the biome for Y-level
-1. I don't know why they do that (probably some dumb reason that may
be a bug in of itself) but returning the first level should be harmless.
Fixes#1683.
Fixes#1650.
Mojang changed the biomes code so that it now can have different
biomes for different Y levels. We need to adjust our logic accordingly,
which is done through some small BiomeDispensary class where we shove
a numpy'd Mojang array in and can then read out the biomes for each level.
Biome data is now stored per-section, which needed some changes on the C
side of things. I didn't change anything in the biome overlay code so
I wouldn't be surprised if it's broken now, but for the time being I'd
rather have 1.15 fixed than some obscure overlay.
Tested to work with 1.14 and 1.15 data. No new biomes have been added
to the code yet.
