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Dev Tools

An in-game authoring aid: build a structure by hand, scan it, and export it as a Java scaffold, a KubeJS script, or a datapack JSON. It automates writing the layer grid by hand; it does not fill in behavior — formation mode, validators, and callbacks are still yours to add. Only the static geometry (layers, symbol keys, core/activation) is captured, and every exported file marks the rest with a TODO.

Enabling

Set devMode = true in config/multilib/common.toml (default false). While off, the dev block, its item, block entity, and menu are never registered — a production build carries no trace of them.

  • Break dev blocks before disabling devMode, or their saved positions load as missing blocks.
  • devMode isn't synced. On a dedicated server, client and server must match, or NeoForge rejects the connection.

When enabled, the Multiblock Dev Block, Dev Wrench, and Preference Wrench appear in the Tools & Utilities creative tab. (The preference wrench is a separate tool for picking which definition an ambiguous block resolves to, not part of the scan/export flow below.)

The dev block

Right-click it (empty-handed or holding anything but the dev wrench) to open its GUI. All fields persist on the block entity across GUI reopens and world reloads:

Field Meaning
Path The structure's id path (e.g. fusion_reactor); also names every exported file.
Display Name Optional translation text; blank falls back to the path.
Offset X/Y/Z Scan-area start, relative to the dev block. Default (0, 1, 0) — one block above.
Size X/Y/Z Scan-area dimensions.

The dev block's own position always counts as air, even if the area overlaps it.

Scanning

Scanning is driven by the auto-detect toggle, not a one-shot button. A scan reads the area into a layer grid (top layer first, same convention as .layer(...)), assigning one symbol per distinct block type in first-appearance order from a 52-symbol alphabet (A–Z, a–z). It's deterministic — an unchanged area always yields the same symbols — and the empty border is trimmed automatically.

Three failure cases, each with its own message:

Failure Cause
Empty area No non-air blocks.
Too many block types More than 52 distinct blocks.
Incomplete multi-part block A door/bed/tall plant has only one half inside the area. Resize to include both.

Auto-detect

The Detect button toggles auto-detect (its label shows the state). While on, the server re-scans the area every devtoolAutoDetectIntervalTicks ticks (default 10), keeping the scan, tag, and HUD list current as you edit blocks. It persists per block and re-registers on world reload.

Render

Render toggles a translucent box outlining the configured area, updating live with the offset/size fields. Persisted, so it reappears after reload.

Show List

Show List toggles a scoreboard-style HUD listing the last scan: the tagged core/activation block, then each distinct block with its count. One list per player at a time. Useful for watching a scan update live alongside auto-detect.

Tagging core/activation

Right-click a block with the Dev Wrench to tag its type. The standard rule applies: a block occurring once becomes the core; one occurring more than once becomes the activation symbol. Right-clicking a tagged type again clears it.

  • Holding the wrench suppresses all other interaction on the block — a wrench click is only ever a tag attempt.
  • Tagging works as soon as the GUI has been opened once, before any scan; occurrences are counted against the live world in the area.
  • Once a scan exists, the block must already be part of it — re-Detect first if you've added a new block type.
  • Multi-part blocks (doors, beds, tall plants) count as one occurrence, so a two-cell door can still be a unique core.
  • Tagging targets a block type; each scan re-resolves it against the fresh grid.

Exporting

Once a scan exists, the three Export buttons write it to disk. Every export uses the fixed namespace devtoolNamespace (default multilib); the Path field supplies only the path half of the namespace:path id and its multiblock.<namespace>.<path> translation key.

Format Written to Result
Java config/multilib/output/<ClassName>.java A MultiLib.define(...) scaffold with layers/keys/core/name filled in, TODOs for the rest. Copy into your mod.
KubeJS kubejs/server_scripts/<namespace>/<path>.js A MultiblockEvents.create(...) script — see KubeJS Integration.
JSON The world's datapacks/<namespace>/.../multiblocks/<path>.json A real datapack definition. The tool scaffolds pack.mcmeta, then enables and reloads the pack, so the structure is detectable immediately.

Each export also writes the Display Name to a lang file (the JSON export uses a client resourcepack under resourcepacks/<namespace>/, since datapacks can't carry translations), plus a standalone <file>.lang.json snippet beside the output for copy-paste.

Re-exporting the same id overwrites without asking. A path collision with a different id is refused with a confirmation prompt; export again to overwrite.

Output directories are overridable via devtoolJavaOutputDir / devtoolKubeJsOutputDir / devtoolJsonOutputDir.

Loading

The Load tab lists every multiblock the tool can find — its own exports in all three formats, plus every multiblock currently registered (Java, JSON, KubeJS). When an id appears in both, the live registered definition wins. Shapeless and PatternProvider definitions are skipped (no static grid).

Loading an entry:

  1. Restores the Path/Display Name fields and scan data.
  2. Resizes the area to the pattern, clears it, and stamps the blocks into the world (re-linking multi-part blocks).
  3. Re-tags the core/activation block if the export had one.
  4. Turns on Render and auto-detect, so the structure appears placed and stays scanned as you edit it.

This makes the block a round-trip loop — open an existing multiblock, tweak it in-world, re-export — not just one-way.

Config reference

All under CommonConfig (config/multilib/common.toml):

Option Default Purpose
devMode false Master switch for the whole dev-tool suite and other debug feedback (ghost-overlay countdown, wrench state chat).
devtoolNamespace multilib Namespace half of every export's id and translation key.
devtoolJavaOutputDir config/multilib/output Java export directory.
devtoolKubeJsOutputDir (empty) KubeJS export directory; empty → kubejs/server_scripts/<namespace>.
devtoolJsonOutputDir (empty) JSON export base; empty → the world's own datapacks/<namespace>.
devtoolAutoDetectIntervalTicks 10 Auto-detect re-scan interval in ticks (20 = 1 second).

See also