21a10ab65e
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. |
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|---|---|---|
| cmd | ||
| internal | ||
| tools | ||
| .gitignore | ||
| CLAUDE.md | ||
| go.mod | ||
| Makefile | ||
| README.md | ||
RegionIO
A Minecraft Java Edition server core written in Go, targeting version
26.1.2 (protocol 775). RegionIO implements the connection lifecycle
(status → login → configuration → play), multiplayer chunk streaming, shared
block editing, persistent worlds, and an overworld generator built on the real
noise_router final_density tree.
Status
- Network: full handshake/status/login (offline mode)/configuration/play state machine with zlib compression, keep-alive, and chunk streaming.
- Registries: 28 synchronized registries + tags, captured verbatim from the 26.1.2 vanilla server and sent during configuration.
- World: revisioned, concurrency-safe chunk snapshots; memoized
level_chunk_with_lightframes; ticket-aware bounded LRU cache; shared frame admission limit; Anvil.mcapersistence with autosave and seed metadata. - Generation: vanilla-derived overworld terrain from the embedded datapack
(
ImprovedNoise/PerlinNoise/BlendedNoise/NormalNoise+ the density function interpreter), 3D multi-noise biomes, surface-rule interpretation, deterministic decoration, and basic template structures. - Gameplay: four-player session registry; player join/leave and movement synchronization; chunk-scoped visibility for players and mobs; shared creative block place/break; broadcast chat; and hotbar item→block mapping.
- Lighting: stored vanilla nibble arrays for sky and block light; horizontal
and cross-chunk propagation; incremental updates after edits; persisted
SkyLight/BlockLight; load-time border reconciliation; and chunk-scopedlight_updatebroadcasts. - Chunk lifecycle: per-client view and prefetch tickets, strict near-first ring streaming, stale-recenter cutoff, explicit client unload packets, and eviction only after the final owner releases a chunk.
- Safety: duplicate chunk generation is coalesced; corrupt stored chunks are not silently regenerated or overwritten; a world cannot reopen with another seed.
Build & run
go build ./...
go run ./cmd/regionio -seed 12345 -port 25565 -viewdistance 2
The world seed defaults to 0; override it with the -seed flag or the
REGIONIO_SEED environment variable. The server listens on 0.0.0.0:25565.
Changing the seed for an existing world directory is rejected. The server caps
the client-requested chunk radius at 2 by default because cold density-based
generation is expensive; raise it with -viewdistance 3 after the surrounding
world has been generated and cached.
Testing
go test ./...
go test -race ./internal/network ./internal/server ./internal/world \
-run 'Test(Integration|BoundaryEdit|PlayerInfo|PlayerRegistry|Concurrent|Incremental|EncodeLight|Cache|Store|Eviction|Region|Ticket|Streamer|LoadSixteen)'
# or run both gates:
make verify
The integration suite exercises four clients across two visibility regions:
join, movement, leaving, mob visibility, and local block/light updates. A
two-client scenario separately covers shared block edits and chat. Concurrency
tests cover simultaneous frame encoding, editing, autosave, cache misses, and
session movement/broadcasts. A 16-client lifecycle test exercises overlapping
ticket ownership, bounded global frame work, packet output, and cleanup after
disconnect. Lighting tests compare the initial flat chunk and a 31x31x31
glowstone propagation volume against fixtures captured from the official
vanilla 26.1.2 server. Optional terrain parity diagnostics compare surface
heights against /tmp/vanilla_ground.json when that capture is present.
v0.4 scope
RegionIO v0.4 is a small creative multiplayer server core, not a complete vanilla gameplay implementation. Player and mob visibility is chunk-scoped, but there is no interest prioritization or delta-movement compression yet. Lighting matches vanilla's block-state dampening, emission, and face-occlusion properties and reconciles persisted borders when chunks re-enter the live cache. Streaming prioritizes Chebyshev rings and abandons unstarted stale work; an already admitted frame calculation completes atomically rather than being interrupted halfway. Unowned clean chunks remain as an LRU warm cache until capacity pressure evicts them. Structures, placed features, mob AI, authentication, inventory, and survival mechanics remain intentionally partial. The density router is vanilla-derived, while biome/surface/decoration layers still contain approximations and require stricter parity fixtures.
Project layout
cmd/regionio/ entry point (config, listener, graceful shutdown)
internal/
protocol/ wire primitives: VarInt, framing, compression, packet IDs
nbt/ NBT encoder/decoder (with modified UTF-8)
registry/ embedded synchronized registries + tags
world/ chunk model, level_chunk encoder, cache, generators, biomes
worldgen/ noise core + density-function interpreter + climate finder
network/ per-connection state machine (handler/conn/play/login/...)
server/ shared core: config, status response, profiles
Notes
The vanilla server.jar and its unpacked libraries//versions/ are not
included (obtain them from Mojang). The embedded data under internal/
(registries, biome parameters, the overworld datapack) is derived from vanilla
reports and is all that is required to build and run.