c6185d88c8
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.
|
||
|---|---|---|
| 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.