SimCity Expansion
Building expansion-pack manager for New-Simukraft-1.21.1
Bring vanilla, Litematica, and WorldEdit structures into the game, convert and install
them as buildable SimuKraft buildings, edit them in a Litematica-style manager, and
share them as one-click zip packs.
Contents
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 <kbd>\</kbd> (backslash) in-game. All bindings are rebindable under the mod's
category in Options -> Controls.
| Action |
Default key |
| Open the build pack manager |
<kbd>\</kbd> |
| Set world selection corner A |
<kbd>[</kbd> |
| Set world selection corner B |
<kbd>]</kbd> |
| Capture the selection as a blueprint |
<kbd>'</kbd> |
| 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 <kbd>H</kbd> 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:
- Look at a block and press <kbd>[</kbd> to set corner A, then <kbd>]</kbd> to set
corner B. The selection box is drawn in the world.
- Press <kbd>'</kbd> to capture the selection and export it to the import directory.
- 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
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
About the old version
- 1.20.1 Forge has been abandoned for development
