Arnis Meld Fork v2.9.0

Arnis Meld Fork 2.9.0

A fork of Arnis by louis-e, tuned for large-scale parallel
generation with the Meld orchestrator. It carries the full
upstream 2.9.0 line and adds the cross-tile machinery that keeps independently built tiles lining up
block for block, so you can generate whole regions as one seamless Minecraft world.

Highlights

• Caught up to upstream Arnis 2.9.0 (in-process tile parallelism + stream-to-disk), seam verified
  intact: 0 of 1024 boundary chunks differ.
• Snow-capped terrain above the real-world snow line.
• Roads-and-ground-only mode (--no-buildings) for a clean base layer.
• Fully offline elevation (--offline, --download-terrain-only, ARNIS_ELEV_ZOOM), no rate
  limits, no no-data holes.
• Big water, shore, and wetland rework that kills the old stepped-water and stray-sand artifacts.
• Lower memory on dense areas (one byte per cell for the common section).

New features

• Snow line. Terrain above the latitude-derived snow line gets a thin snow layer with a soft
  edge. Honours --elevation-min/--elevation-max, so the cap lands at the same height across tile
  seams, and it skips water and shore.
• Parking like roads. Speckled asphalt (honouring surface=*), white lane markings, and a slim
  metal lamp. The lamp is gated behind buildings, so --no-buildings draws only the flat pavement.
• Automatic flat low-scale bridges. At --scale 0.3 or lower, bridges become a flat one-block
  deck instead of a collapsing arch.

Flags and options

• --no-buildings (alias --no-structures): drop buildings and building-adjacent features, keep
  roads, rail, water, land cover, terrain, and parking.
• --tile-invariant-rendering (alias --seed): a building straddling two tiles renders identically
  in both. arnis ... --seed 42
• --road-detail max|clean|compact: trade road detail for legibility at small scale.
• --overpass-url: priority-ordered Overpass endpoints that replace the public mirrors.
• --download-only + --save-json-file: fetch a region's OSM once, then feed many runs with --file.
• --download-terrain-only: warm the AWS terrain cache for a bbox in one pass, then exit.
• --offline (alias --elevation-cache-only): serve elevation from cache only, never re-download.
• ARNIS_ELEV_ZOOM=13: cap the terrain zoom. z13 keeps the full ~30 m signal, dodges the z14/z15
  no-data holes, and pulls far fewer tiles. (PowerShell: $env:ARNIS_ELEV_ZOOM='13')
• --master-origin-lat / --master-origin-lng: anchor every tile to one global ruler. Pass both.
• --elevation-min / --elevation-max: pin one shared real-world height range in metres. Pass both.

Water and shore rework

A multi-pass water, underwater, shore, and wetland system: flat per-component water surface,
single-cell sand shore swap, depth-tiered beds, water carving under bridges, a stoney-shore ring, and
thin-land drown. Resolves the long-running stepped-water, double-slope, air-hole, and stray-sand
artifacts. Adds 9 block IDs (256 to 265) and widens block IDs to u16.

Engine and performance

• Merged 53 upstream louis-e/arnis commits: tile parallelism, stream-to-disk eviction, mimalloc, the
  large-area warning, and the GUI ETA, with the cross-tile seam kept intact.
• One byte per cell for the common section. Widening to u16 had doubled every full section's
  backing vector; storage now uses one byte where every id fits and the wide form only where a high
  id is present. Reads, writes, and the seam hash are representation-independent (verified by a
  round-trip and a Full-vs-FullWide test).
• Product renamed to "Arnis Meld Fork"; GUI footer credits louis-e and Teddy563.

Fixed

• Parallel-safe terrain fetch (6 retries with backoff, per-tile jitter, atomic temp-then-rename
  writes, retry-missing rounds) that kills the staircase seam under heavy concurrent fetching.
• i32 corner-sum overflow panic on far-from-origin master coordinates.
• Cross-tile coordinate drift under master-origin (anchored at origin_lat; single-world output is
  byte-identical).
• Tree trunk apex cap, Minecraft 1.21.4 to 26.1.x datapack schema overlays, and GUI disk-probe fixes.

Downloads

Grab the build for your platform from the Assets below: Windows (arnis-windows.exe), Linux
(arnis-linux, or the arnis-linux.AppImage), and macOS (arnis-mac-intel, arnis-mac-arm64).

Try it at scale with Meld

Arnis builds one area at a time. Meld drives this fork to
build whole cities, countries, and continents as one seamless world: it tiles your selection, builds
the tiles in parallel, and melds them with no seams and no height cliffs.

Try Meld now · meldmc.com

Credits

Original Arnis by louis-e. Meld fork by
Teddy563. Respect the upstream Arnis license.