Generate large Minecraft worlds with Arnis
Arnis turns a real place into a Minecraft world from OpenStreetMap data. It is excellent at what it does, and it builds one area at a time.
Meld runs Arnis over a whole region. It cuts the map into tiles, builds many tiles at once, and joins them into a single world where you cannot see the joins. Same generator underneath, much bigger result.
Meld is free and open source, and it is built on a fork of Arnis by louis-e.
What Meld adds to Arnis
- Bigger areas. Pick a city, a county, or a whole country. Meld works out the tiles for you.
- Many builds at once. Tiles are generated in parallel instead of one after another, so a big area finishes in a fraction of the time.
- One world, no seams. Tiles are joined so the terrain lines up. No walls, no steps in the ground, no repeated strips.
- Stop and continue. Close the app, come back later, carry on. Finished tiles are not rebuilt.
- Taller worlds. Real mountains do not fit in the default Minecraft height. Meld can fit the world height to the terrain, so peaks stay peaks.
- A map you click. Draw your area on a map instead of typing coordinates.
How it works
- Pick an area on the map.
- Meld splits it into tiles that line up with Minecraft region files.
- Each tile is built by Arnis, several at the same time, using all the cores you allow.
- Meld joins the tiles into one world folder.
Every tile is built with the same origin and the same terrain heights, which is what makes the result look like one world rather than a grid of separate builds.
How much faster
Measured on one PC over the same area of Bucharest, 1024 regions: a single Arnis build takes about 8 minutes 8 seconds. Meld does the same area in about 1 minute 50 seconds.
The gain comes from using the whole CPU instead of one build at a time, and it grows with the size of the area. Full numbers and method are on the benchmark page.
Why the tiles line up
Splitting a map into tiles is easy. Making the tiles match at the edges is the hard part. Three things do it:
- One origin for the whole world. Every tile measures from the same point, so a road that crosses a tile edge stays straight.
- One height range for the whole world. Tiles share a single elevation scale, so the ground does not step up or down at a border.
- Decisions based on position, not on the tile. What gets placed at a spot depends only on where that spot is in the world. Two tiles that overlap the same ground produce the same blocks.
The last point is tested, not assumed. Two overlapping tiles are generated as separate builds and compared block by block; they match exactly.
What you keep from Arnis
Meld does not replace Arnis. It drives it. Buildings, roads, rivers, railways, land cover and terrain all come from Arnis, and the fork stays in step with the original.
Every setting the fork adds is optional. Leave them alone and each tile is generated the way plain Arnis would generate it.
Start here
- Try the demo. It is the real interface with a simulated backend, so nothing is downloaded or generated.
- Read how it works for the full picture.
- Download Meld from GitHub and build your first area.
Common questions
Can Arnis generate a whole country on its own?
Arnis builds one area per run. For a country you would run it many times and stitch the results yourself, which is where the edges usually go wrong. Meld does the splitting, the running and the joining for you.
Do I need to install Arnis separately?
No. Meld ships with the generator it needs.
Is this a replacement for Arnis?
No. It is a way to run Arnis over a much larger area. Credit for the generator goes to louis-e and the Arnis contributors.
How large can an area be?
Large enough that disk space and time become the limit rather than the software. Worlds of several thousand regions have been built this way.
Can I make the world smaller than real life?
Yes. You choose a scale, from real size down to a fraction of it, so a whole country can fit in a world you can actually cross.
Does it work offline?
Yes. Map data and elevation can be downloaded once and reused, which also avoids rate limits on big builds.