Every air block below y=63 was turned into water. That is one line of code and
it cost the entire underground: no dry caves, no lava lakes, no air pockets, a
solid block of water from the sea floor to bedrock.
Vanilla decides fluid per position instead. Aquifer centres sit on a jittered
16x12x16 grid; each gets a fluid level and type from the floodedness and spread
noises, with centres near open sky inheriting the sea and buried ones getting a
much lower randomised level or nothing at all. A position takes its nearest
centre's fluid unless the barrier noise raises enough pressure between the two
or three nearest centres to seal it back to stone. Deep centres turn to lava.
Porting it means fixing the order of generation, not just adding a file. Vanilla
resolves stone/water/lava/air during the density pass and only then runs the
surface rules over a finished column; we did it the other way round, which is
what forced the unconditional flood in the first place. fillVanillaColumn now
asks the aquifer per position, and applySurfaceRule walks the finished column
carrying the bookkeeping SurfaceSystem carries: air resets the counters, a fluid
records its water height, and stone gets a depth from the top of its run plus
one from the bottom, found by looking ahead to the next non-stone block below.
That last one fixes stone_depth's ceiling form, which had no bottom-up depth to
work with and was testing the top-down one instead -- fourteen rules in the
overworld tree use it to dress cave roofs. The floor form is unchanged: vanilla
counts from 1 and compares against 1 + offset, we counted from 0 and compared
against offset.
The aquifer grid is built eagerly per chunk rather than lazily, because our
columns fill concurrently; every cell is a pure function of its grid coordinate
and every cell in the computed range gets consulted anyway. Cost is ~0.5% of
chunk generation, most of it absorbed by the shared preliminary-surface cache.
Inland caves go from 100% water to 3.8%, and lava exists for the first time.
cmd/gendump grows a census that would have failed loudly before, and
TestCavesAreDry guards it in the suite.
The overworld noise_router ships fourteen keys; we read six. The eight left on
the floor are exactly the ones the aquifer, the ore veins and the preliminary
surface estimate need, so every one of those subsystems has been impossible to
write.
Wire the rest of the router into OverworldDensity: barrier,
fluid_level_floodedness, fluid_level_spread and lava for the aquifer,
vein_toggle/vein_ridged/vein_gap for the veins, and preliminary_surface_level
for both. Two node types were missing and are added with them --
minecraft:invert (the reciprocal, not negation: Mapped.Type ordinal 5 is
1.0/input) and minecraft:find_top_surface, which walks down from an upper bound
in cell_height steps looking for positive density.
PreliminarySurfaceLevelAt wraps that node the way NoiseChunk does: quart-align
the column, then memoise. The cache is per generator rather than per chunk
because the aquifer samples columns up to three chunks away, so neighbours
overlap heavily -- with a shared cache a chunk costs a few dozen evaluations
instead of a few thousand.
Also lifts sea_level, min_y, height and the aquifers/ore-veins flags out of the
settings file, and adds PositionalRandomFactory.At for the aquifer cell centres
(Mth.getSeed hashed into the low half of the factory seed).
No generator output changes yet: nothing reads the new keys.
Replaces the biome-blind fillVanillaColumn heuristics with a full
interpreter for the overworld surface_rule tree (already embedded in
overworld.json): block/sequence/condition/bandlands rules plus all 11
condition tests (biome, steep, hole, water, temperature, y_above,
stone_depth, noise_threshold, not, vertical_gradient,
above_preliminary_surface).
- worldgen/blockids.go: name(+Properties)→network-ID table for surface
blocks (grass/sand/terracotta/mycelium/podzol/coarse_dirt/sandstone/
calcite/snow/ice/...), with snowy property variants.
- worldgen/surface.go: rule-tree parser + interpreter + SurfaceContext;
LoadOverworldSurfaceRule caches the seed-independent tree.
- loader.go: OverworldDensity.SurfaceRule() exposes the parsed tree.
- biome_lookup.go: BiomeNameAt returns the biome name for biome tests.
- vanilla.go: samples the 2D climate + biome before column fill, threads
the rule tree and biome name into fillVanillaColumn, and applies it
top-down with stone as the default for non-matching (deeper) blocks.
The above_preliminary_surface gate uses an inclusive bound so the top
solid block reaches the biome dispatch.
- Performance: one per-column RNG and a reused SurfaceContext keep the
overhead to ~+13ms/chunk (71ms vs 58ms baseline), within the gate.
- Chunk stores per-section biome arrays (64 cells/section); flat generators
keep the uniform single-valued fallback.
- New writeBiomePalette uses min 1 bpe and direct at registry width (65 biomes).
- Climate sampler splits 2D axes (sampled once per column) from 3D depth
(per cell), keeping per-cell cost to a single density-function compute.
- Full biome parameter table (surface + underground twins + lush/dripstone/
deep_dark caves) with depth as a true range, not a binary layer.
- fillBiomes3D fills the 1536 cells/chunk in parallel; <0.3ms overhead vs
baseline chunk gen (benchmark-verified).
- Tests: cave-biome resolution, per-cell variation, flat-world regression,
registry-range validity, plus chunk-gen and per-cell benchmarks.
