SimCity Expansion

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Contents

• Overview
• Features
• Requirements and installation
• Opening the manager
• The manager
• Structure editor
• Capturing builds from the world
• Build packs
• Structure formats
• Directory layout
• Commands
• Documentation
• Building from source
• License
• Acknowledgements

Overview

SimCity Expansion is a NeoForge mod for Minecraft 1.21.1 that adds a complete building expansion-pack pipeline to New-Simukraft-1.21.1 (a city-building mod). It lets you import structures from three common formats, convert them into SimuKraft's buildable format, organise and edit them through a Litematica-style manager, and package them as portable zip packs for one-click install and sharing.

Integration with SimuKraft is a pure file-system convention — the mod writes .sk and .nbt files under <game dir>/simukraftbuilding/<category>/ — so there is no compile-time dependency on SimuKraft. The manager is built on Minecraft's own GUI toolkit and needs no extra library, and the command interface runs on a dedicated server as well.

Features

• Three structure formats — vanilla .nbt, Litematica .litematic (multi-region auto-merge), and Sponge/WorldEdit .schem (v1/v2/v3), all converted to SimuKraft's vanilla buildable format on install.
• Robust conversion — older structures are upgraded through the game DataFixer, missing mod blocks are detected against the registry, and block-entity contents (chest inventories, signs, and so on) are preserved (entities are not).
• Litematica-style manager (open with \) — file tree, fixed-width info panel, material list, and layered previews: embedded thumbnail, real-block 3D scene, isometric voxel view, and top-down map.
• Full structure editor — place / break / pick / replace, brush painting, box selection with fill / frame / hollow / expand, copy / cut / paste, rotate and mirror, symmetry axis, undo / redo, slice planes, and preset camera views; export to .litematic or save and install directly.
• Capture from the world — mark two corners in-game, capture the selection as a blueprint, and optionally include block-entity contents.
• Zip pack ecosystem — manifest-tracked install / uninstall, one-click export of installed buildings into a shareable pack, an optional pack icon and an index.json file manifest, and pass-through of SimuKraft native job/trade definitions (format v2).
• No hard dependencies — the manager runs on Minecraft's own GUI toolkit and SimuKraft is integrated purely through the file system, so neither is a compile-time dependency.
• Server-friendly — the /buildpack command (operator level 2, with tab-completion) installs loose files and packs and captures regions on dedicated servers, reusing the same conversion pipeline as the GUI.
• Localised — English, Simplified Chinese, and Traditional Chinese; numbers, dates, and file sizes are formatted per the active game language.

Requirements and installation

Requirement	Version
Minecraft	1.21.1
NeoForge	21.1.233 or newer

Place the jar in your mods/ folder — there are no other mod dependencies. The in-game manager works out of the box on a client; on a dedicated server the jar loads headless and exposes the /buildpack command.

Opening the manager

Press \ (backslash) in-game. All bindings are rebindable under the mod's category in Options -> Controls.

Action	Default key
Open the build pack manager	\
Set world selection corner A	[
Set world selection corner B	]
Capture the selection as a blueprint	'
Toggle "include block-entity contents"	unbound
Clear the world selection	unbound

The manager

The left panel has three tabs:

• Import Files — loose .nbt / .litematic / .schem files in the import directory.
• Packs — zip build packs in the import directory, shown as an expandable tree (pack -> category -> building). Any building can be previewed and read directly from the zip, without extracting it first.
• Installed — buildings already present in SimuKraft's building directory.

The info panel on the right shows metadata rows, a preview, a material list (counted by block type, with missing blocks flagged), and a .sk metadata form (editable on the Import tab, read-only elsewhere). It supports drag-and-drop import, search, sort, batch install, and two-click delete. When you browse a pack that ships an icon, the icon is shown in the preview area.

Structure editor

Open a structure in the editor to refine it before installing:

• Edit — place, break, pick, and replace blocks; paintbrush with adjustable size and paint strokes; remove or replace a whole block type at once.
• Selection — box-select a region (click two cells or drag a box face), then fill / frame / hollow / expand / clear it, with copy, cut, and paste.
• Transform — rotate 90 degrees and mirror along any axis, with a symmetry axis for mirrored editing.
• History — undo and redo.
• View — cycle slice planes, fit and focus the selection, preset camera angles, grid and gizmo toggles, and perspective toggle.
• Output — Save as New, Save and Install, or Export .litematic.

Press H inside the editor for the full shortcut list.

Capturing builds from the world

Build something in your world, then turn it into a blueprint without leaving the game:

1. Look at a block and press [ to set corner A, then ] to set corner B. The selection box is drawn in the world.
2. Press ' to capture the selection and export it to the import directory.
3. Optionally bind the "include block-entity contents" key to capture chest inventories and similar data, and the "clear selection" key to reset the corners.

The same operation is available on servers via /buildpack capture (see Commands).

Build packs

Buildings are grouped into five fixed categories: residential, commercial, industry, public, and other.

• Install / uninstall — installing a pack converts every building into the matching category directory and records a manifest in simcity_expansion/installed_packs.json, so uninstalling removes exactly the files that pack added.

• Export (Installed tab -> Export) — packages the listed buildings (respecting the current search filter) into a zip. Options:

  • include .sk metadata,
  • include SimuKraft job/trade JSON,
  • include an icon — tick the box and leave the path blank to auto-render one from the first building's preview, or supply a custom PNG path.

  An index.json file manifest (each packed file with its type, category, size, and SHA-256) is always written at the zip root.

• Manifest — pack.json (format 2) carries id, name, version, author, description, an optional icon, and a generated timestamp.

The full pack specification (directory layout, pack.json, .sk / .meta.json metadata, native job/trade JSON, icon.png, and index.json) is documented in docs/pack-format.zh.md.

Structure formats

Extension	Source	Conversion on install
.nbt	Vanilla structure block template	Installed as-is; old versions auto-upgraded
.litematic	Litematica projection	Multi-region merge into one bounding box; reads embedded name / author / creation time / thumbnail
.schem	Sponge / WorldEdit schematic	v1, v2, and v3 supported

All formats are converted to vanilla .nbt on install (SimuKraft's build system only reads the vanilla format). During conversion the structure is DataFixer-upgraded to the current game version, block-entity positions are remapped and preserved, the palette is checked against the registry for missing blocks, and the merged volume is capped at 16,000,000 blocks.

Directory layout

<game dir>/
├── simcity_expansion/
│   ├── import/                 import directory (drop loose files and zip packs here)
│   ├── export/                 exported build packs
│   └── installed_packs.json    installed-pack registry
└── simukraftbuilding/<category>/   SimuKraft building directory (install target)

Commands

All /buildpack subcommands require operator level 2 (game masters) and offer tab-completion.

Command	Description
/buildpack list	List the files in the import directory
/buildpack packs	List installed packs
/buildpack install <file> [category] [name]	Install a loose structure file
/buildpack installpack <zip>	Install a whole zip pack
/buildpack uninstallpack <id>	Uninstall a pack by its id
/buildpack activate <zip>	Serve a pack to SimuKraft virtually (no install) — requires SimuKraft
/buildpack deactivate <id>	Stop serving an activated pack
/buildpack active	List currently active packs
/buildpack capture <from> <to> [name] [format]	Capture a region into a blueprint

Documentation

Document	Audience
Usage guide	Players: import, install, manage, export
Pack format spec v2	Pack authors: layout, pack.json, metadata, conversion

Chinese versions are also available: usage.zh.md and pack-format.zh.md.

Building from source

The project uses the Gradle wrapper and a NeoForge ModDevGradle toolchain (JDK 21).

./gradlew build

The built jar is written to build/libs/.

License

All Rights Reserved. Copyright © 2026 xinian. This source is published for reference; it is not licensed for redistribution or derivative works without permission. When using in a modpack, you must link back to the original link.

Acknowledgements

• New-Simukraft-1.21.1 — the city-building mod this expands.
• devins-badges — the badge artwork in this readme.

About the old version

• 1.20.1 Forge has been abandoned for development