One World

One World

Normally every generation creates a new world. With One World turned on, every area you generate is added to the same Java world instead, at its real position. Generate your neighbourhood today and the next town over tomorrow, and they join up as if they'd been generated together.

How to use it

In the GUI: turn on One World under Settings > World. Below the format buttons you then see which world the next area goes into and how many areas it already has. The world is called "Arnis One World" unless you give it another name. Areas you already generated are shown on the map, so you can see where to continue.

On the command line:

arnis --one-world --output-dir="C:/YOUR_PATH/.minecraft/saves" --world-name="My City" --bbox="min_lat,min_lng,max_lat,max_lng"

Here --output-dir is your saves folder, not the world folder. --world-name picks the world inside it, and a world that doesn't exist yet is created.

What's different

• Real positions. The world uses one fixed Web Mercator frame, centred on your first area. Every area after that is placed in the same frame, so neighbouring areas line up block for block.
• Whole chunks. Each requested area is snapped outwards to full chunks, so areas meet cleanly at chunk borders. Elements that cross a border are built with some margin, so a building on the seam comes out whole on both sides.
• The first area decides. World scale, ground level and whether the world has terrain are fixed by the first run. A later area with a different scale or terrain setting is refused, with a message telling you why. The terrain height multiplier and the elevation source (normal or legacy) also stay what the world was created with.
• Extended build height. A new One World always gets the extended build height data pack, so any place on Earth fits, from the coast to the Alps.
• Regenerating an area. If your new area overlaps chunks that already exist, the GUI asks before it generates them again. Anything you built there in Minecraft is replaced.
• Spawn. The world's spawn is set by the first area. Later areas only move it if you place a spawn point inside the new area.
• Leave the world first. Arnis can't add to a world that's open in Minecraft. Leave the world or close the game, then generate.

Limitations

One World is Java only and Earth only, and it covers latitudes up to 85 degrees north and south. A few things are turned off or changed in this mode:

• Rotation is off, since the world has to stay aligned to real coordinates.
• The Gameplay Extras aren't available yet, because each area would overwrite the data pack of the one before.
• The Voxy LOD cache isn't generated.
• Building facades: the preset photos are off, and Mapillary facades are built as blocks instead of photo panels, since both would replace the world's resource pack on every run.

How the world is stored

The world folder has an extra file, arnis_one_world.json, next to level.dat. It stores the frame (origin and scale), the settings the world was created with, the elevation mapping all areas share, and a list of every area with its coordinates and the Arnis version that generated it. Don't delete it, or Arnis won't recognise the folder as a One World anymore. Preview images of the areas are kept in arnis_one_world/previews.

More about the coordinate frame is on the Coordinate System page.