BlueMap Structures Paper

Chunkbase-style, seed-derived structure markers for BlueMap, as a Paper/Purpur plugin. Villages, strongholds, ocean monuments and 18 other structure layers appear as toggleable marker layers on your web map — computed from the world seed, without loading or generating chunks.

A Paper-API reimplementation of the Fabric mod mc-bluemap-structures (which cannot run on Paper/Purpur servers).

Features

21 structure layers — village, desert pyramid, jungle temple, swamp hut, igloo, pillager outpost, ancient city, trail ruins, trial chambers, ocean ruin, shipwreck, ruined portal (overworld & nether), ocean monument, woodland mansion, nether fortress, bastion remnant, end city, buried treasure (opt-in), mineshaft (opt-in), stronghold.
Per-layer toggles in the BlueMap sidebar, each with its own icon — generated on first startup from Mojang's official client assets (downloaded by your server directly from Mojang, cached in the plugin data folder; no third-party artwork is bundled or redistributed).
Copyable /tp command in every marker popup.
Zoom-gated visibility for dense layers (shipwrecks, ocean ruins, …) to keep the web app responsive.
Seed-derived, biome-validated — candidate positions come from vanilla's own placement math (same approach as Chunkbase), then each candidate is checked against the world's noise-based biome source (has_structure/* biome tags) through the Paper API. No chunks are loaded or generated at any point.
TPS-friendly — the whole scan is pure math on an async thread and finishes in milliseconds per world; the main thread only publishes the markers.

Requirements

Paper or Purpur, Minecraft 26.1 or later (api-version: '26.1'; built against paper-api 26.1.2)
Java 25
BlueMap 5.x (soft dependency — the plugin idles when BlueMap is absent)

Install

Drop BlueMapStructuresPaper-x.y.z.jar into plugins/.
Restart. On every start the plugin recomputes the markers from each mapped world's seed (milliseconds per world; totals in console) and registers the marker layers.

On the first start the plugin also downloads the Minecraft client jar for your server's version from Mojang (piston-meta.mojang.com, the same source launchers use) and crops the marker icons out of its textures; both the jar and the generated icons are cached under plugins/BlueMapStructuresPaper/. If the download fails (offline server), markers still work with BlueMap's default POI icon and the plugin retries on the next start.

Configuration

plugins/BlueMapStructuresPaper/config.yml:

areas:                     # scanned squares (union of all entries, deduplicated)
  - center: origin         # origin (0,0) | spawn | {x: <block>, z: <block>}
    radius-blocks: 5000    # half-side of the square

#worlds:                   # per-world overrides (replace the default list entirely)
#  resource:
#    areas:
#      - center: spawn
#        radius-blocks: 2000

layers:                    # one toggle per structure layer
  village: true
  # ...
  buried_treasure: false   # opt-in: ~0.01/chunk → thousands of markers at radius 5000
  mineshaft: false         # opt-in: ~0.004/chunk → 1500+ markers at radius 5000

The legacy top-level radius-blocks: 5000 form still works as shorthand for a single origin-centered area.

Markers are recomputed from the seed on every start (it costs milliseconds), so config changes apply on the next restart — there is no cache to clear.

How it works

Structure positions are computed from the world seed with vanilla's placement algorithm (random-spread grids per structure set, concentric rings for strongholds), then validated against the server's noise-based biome source via the Paper API — the same technique as Chunkbase's Seed Map, and the reason no chunks need to exist. An earlier prototype used World#locateNearestStructure; it turned out to sync-load chunks per candidate cell and stall the server (see issue #3). See docs/DESIGN.md for the details and docs/REQUIREMENTS.md for the refined requirements.

Building

./gradlew build          # plugin jar at plugin/build/libs/
./gradlew :core:test     # pure-logic tests only (no Paper repo access needed)

Related projects

mc-bluemap-structures — the Fabric original this plugin reimplements (structure-catalog reference data, see THIRD_PARTY_NOTICES.md).
BlueMapStructures — Paper-based alternative that reads generated chunks from disk instead of predicting from the seed.

License

MIT — see LICENSE. Third-party provenance (reference data from mc-bluemap-structures, runtime-generated icons from Mojang client assets, seed-math provenance) is documented in THIRD_PARTY_NOTICES.md.