Documentation

How Meld turns a map selection into one seamless Minecraft world. Start here, then pick a guide that explains how each piece works.

What Meld is

Meld is a slim orchestrator around a custom Arnis fork. Arnis converts one OpenStreetMap bounding box into one Minecraft world. Meld adds the thing Arnis cannot do on its own: areas bigger than a single run. It tiles the area into a grid, builds the tiles with many Arnis runs at once, and melds them into one world with the same terrain height and building style everywhere.

It is one Flask process, one single page map UI, and a thin worker pool. A few hundred lines, not a framework.

How a build flows, end to end

You draw an area on the map. Meld does the rest in a few clear steps:

1. It picks an origin, one fixed anchor that every block coordinate is measured from.
2. It runs a quick elevation survey and locks one height range, so the land lines up everywhere.
3. It splits the area into cells that fall on region file boundaries, so seams land in clean spots.
4. It downloads the area's map data once and shares it to every cell, so nothing gets rate limited.
5. It builds many cells in parallel with the Arnis fork, all using the same origin, seed, and height lock.
6. It merges each finished cell into one master world, keeping only the part each cell owns.
7. A drift guard refuses any cell that does not line up, so a built world is never corrupted.

The result is one Minecraft world with no cliffs and no seams. The guides below explain each piece.

Quickstart

One thing has to be installed first: Python 3.9 or newer. A one-click launcher does the rest, so it works the same on Windows, macOS and Linux.

1. Get the code:

   git clone https://github.com/Teddy563/meld
   cd meld

2. Start it for your operating system:
   • Windows: double-click meld.bat.
   • macOS: double-click meld.command in Finder. The first time, right-click it and choose Open once to get past Gatekeeper.
   • Linux: run ./meld.sh.
   The launcher builds a private .venv, installs the dependencies, fetches or builds the matching arnis generator for your machine, then opens http://127.0.0.1:5630. Re-running is instant. To see what is installed or missing without changing anything, run python meld_launch.py --check.
3. Draw a rectangle on the map, or search a place. Meld auto centers the origin, tiles the selection into cells, and runs an elevation survey.
4. Pick a cell size (regions per cell), then hit Generate world. Open the world in Minecraft from the save location shown in the panel.

Manual install (optional)

To wire it up by hand instead:

pip install -r requirements.txt
python server.py        (open http://127.0.0.1:5630)

Put a matching arnis binary next to server.py (on macOS and Linux it must be named arnis, no .exe), or download it from the Teddy563/arnis releases. Meld auto finds it at ./arnis, ../arnis, or the fork's target/release/ build.

The guides

Each page explains the why, the mechanism, and how to use it in the app.

Looking for what changed between releases? That lives in the changelog.