LoadResolvedTemplate parses the extracted .nbt files with every palette
entry resolved to concrete state IDs through an injected resolver, and
TransformBlockPos reproduces StructureTemplate.transform's mirror-then-
rotate order around the pivot, including all three quarter-turn cases
read off the bytecode. MthGetSeed gives processors their per-block
positional Legacy stream. Verified against the real ruined_portal
templates: every block lands inside the declared size for all eight
mirror/rotation combinations.
Loads the 26.1.2 structure datapack: 20 structure sets, 34 structure
definitions, and the worldgen biome tags they reference. Random-spread
placement follows RandomSpreadStructurePlacement byte for byte — region
floorDiv by spacing, one Legacy stream salted per region, two
spread-type draws for the offset — and the four legacy frequency
reducers keep their exact draws, including the hardcoded buried-treasure
salt and the outpost's discarded full-range int.
Verified against the fixture: on seed 12345 the ruined_portals set
claims exactly chunk (1,0), the chunk whose captured blocks carry the
ruined portal's obsidian, gold, and crying obsidian. TestStructure-
PlacementGrid pins that plus village separation invariants.
Ports MonsterRoomFeature from bytecode with vanilla draw order and loop
structure: shell validation (solid floor and ceiling, one to five open
side columns), interior cave_air carving, cobblestone walls with the
mossy three-in-four floor roll drawn only where vanilla draws it, chest
placement faced away from its single opaque neighbour with the loot-seed
long consumed even though block entities are not modelled yet, and the
spawner's one-draw mob pick. Writes go through Feature.safeSetBlock
semantics against #minecraft:features_cannot_replace, captured verbatim
from the jar into the embedded datapack data.
The pass slots between geodes and the ores so the rooms' cave_air
pockets exist before ore ellipsoids roll their air-exposure discards.
The committed fixture's four chunks happen to contain no dungeons, so
measured parity holds at 98.028%, but the generator's output can differ
elsewhere: generatorVersion bumps to 22.
The router's noise caves are one kind of cave. The other kind -- the long
winding tunnels with rooms and side branches, and the ravines that cut down
through the terrain -- is walked, step by step, by a random source, and none of
it existed.
The shape of the work is unusual enough to state plainly. To carve one chunk,
vanilla replays every carver seeded in the 17x17 chunks around it and keeps only
what lands inside, so the same tunnel is walked up to 289 times across a world.
That redundancy is the point: it is what lets a chunk be carved without
generating its neighbours, which is the only way carving fits a generator that
produces one chunk at a time. A carve-once-write-into-neighbours design would be
cheaper and would not reproduce vanilla's mask and ordering.
Two primitives had to be right before any of it could be, and both are pinned
against values captured from the jar:
* setLargeFeatureSeed, which decides which chunks start a cave. It combines
its two products with XOR; setDecorationSeed, which it otherwise resembles,
uses addition and forces the low bit. Getting them the wrong way round moves
every tunnel in the world and nothing complains.
* Mth.sin and Mth.cos, which are a 65536-entry lookup table and not libm.
Mth.sin(-1.0) is -0.8414514 against Math.sin's -0.8414709848078965, and a
tunnel that walks by adding cos(yaw) a hundred times ends up somewhere else
entirely if that difference is smoothed away.
Carving lands between the surface pass and decoration, where vanilla puts it,
and both neighbours matter: the surface rules must already have placed grass for
a cave mouth to be retextured, and decoration must come after so nothing is
planted over a hole. The heights decoration plants against are recomputed
afterwards, which is why vanilla re-primes its heightmaps at the start of the
feature step.
The configs are extracted from the jar rather than transcribed, along with the
flattened #minecraft:overworld_carver_replaceables tag, so the probabilities and
Y ranges are data. Open volume below y=60 rises 28% over sixteen sampled chunks,
tunnels cut at or below y=-56 fill with lava rather than air (869 blocks, no
air), and the cost is inside the noise floor of the density pass.
