modgen mod for minetest

Overview

Allows you to export a part of the map as a standalone mod which can be used as a mapgen

Api docs: https://buckaroobanzay.github.io/modgen/

Demo: https://github.com/BuckarooBanzay/mesecons_lab

Features:

• Map-as-a-mod export
• In-place saving after export
• Autosave
• Autoupdate map in already generated worlds

Commands

• /pos1, /pos2 Set opposite corners of the export map
• /export [fast] Exports the map as a standalone mod into ${worldfolder}/modgen_mod_export
• /modgen_stats Returns some stats about the exported chunks and size
• /autosave [on|off] enables autosave feature (warning: may not work on some worldedit commands)

In-place saving

After an initial mod-export the resulting mod can be edited live and in-place if the modgen mod is also present (optional).

To enable the saving directly into the exported mod you have to add it to the "trusted_mods" setting:

secure.trusted_mods = modgen

Afterwards if you mark a region and execute /export the chunks are written to the exported mod itself

Note

After exporting, the mod won't have a name field in mod.conf, which
needs to be added in order for Minetest to detect and run the mod properly.

Ignored nodes

Per default the ignore node is ignored from export/serialization (mapped to air internally) If you want more nodes to be excluded from the resulting export you can add the group modgen_ignore to them:

minetest.register_node("mymod:mynode", {
  groups = {
    modgen_ignore = 1
  }
})

Or override a node from another mod:

minetest.override_item("other_mod:other_node", {
  groups = {
    modgen_ignore = 1
  }
})

Autoupdate

You can provide updates to an already generated world if the following setting is enabled in the import-mod/world settings:

import_mod.auto_update.enabled = true

This works by comparing the modified-time of the generated chunk (written in the mod-storage) with the mtime of the chunk in the import-mod. The updated area will be deleted with minetest.delete_area and re-generated automatically.

Technical notes

Chunk export format

Chunks saved in ${import_mod}/map/chunk_${x}_${y}_${z}.bin

1 byte:                       serialization version
1 byte:                       number of mapblocks in this chunk (#mapblocks)
4 bytes:                      modification time of this chunk
4096 * 2 * #mapblocks bytes:  node_ids of the mapblocks in (4096 * uint16) portions
4096 * #mapblocks bytes:      param1 data of the mapblocks
4096 * #mapblocks bytes:      param2 data of the mapblocks
remaining bytes:              chunk manifest in json format

Chunk manifest

Json-file in the following format:

{
  "mapblocks": [{
    "pos": {
      "x": 10,
      "y": -1,
      "z": 4
    },
    "has_metadata": true,
    "metadata": {
      "meta": {},
      "timers": {}
    }
  }],
  "mtime": 1649956501
}

NOTE: the mapblocks[].pos field references absolute world-positions in mapblocks

Global manifest

Saved in ${import_mod}/manifest.json

Json file that serves as an index to look up global infos:

• Amount of chunks and bytes saved
• Last modification time
• Node-ID mapping
• Max- and min-bounds of the chunks saved
• Modgen version used to save this map
• UID of the map (gets saved in the mod_storage of the world to prevent mod-misplacement)

{
  "chunks" : 17,
  "mtime" : 1649956501,
  "next_id": 82,
  "node_mapping": {
    "access_cards:palm_scanner_off": 25,
    "air": 0,
    "default:chest": 53,
    "digilines:wire_std_00100000": 72
  },
  "bounds": {
    "min": {
      "x": 0,
      "y": 0,
      "z": 0
    },
    "max": {
      "x": 0,
      "y": 0,
      "z": 0
    }
  },
  "size" : 184548,
  "uid" : "970683",
  "version" : 3
}

Export versions

Major versions with breaking changes:

• Version 1: Initial release
• Version 2: Reordered export axes from x-y-z to z-x-y (30% size decrease)
• Version 3: Export whole chunks (50% size decrease)
• Version 4: Manifest with easy accessible mtime info

To migrate between the major versions export everything into the world and re-import with the new version

Testing

Requirements:

• Docker
• docker-compose

Usage:

docker-compose up --build

License

• Code: MIT
• Textures: CC-BY-SA 3.0 (http://www.small-icons.com/packs/16x16-free-application-icons.htm)