Getting started

What you need to play mods, to make them, and where everything goes.

Playing mods

Install the port

Install Jet Force Gemini: Recompiled (its Releases page has the downloads) and point it at your own US ROM.

Put the mod in the mods folder

Copy the .nrm into the port’s mods folder (next to the game’s executable), or install it from the launcher’s Mods page.

Turn it on and order it

Enable it in the Mods list (launcher or in game). Higher in the list wins when two mods change the same thing (see When mods meet).

Play

Data mods, scripts and planets apply when the game starts; texture packs apply at once.

Where to look when something’s off: bin/jfg_mods.log records every pack the game loaded, what it replaced, the numbers its levels got, conflicts, and script errors.

Making mods

You need	For
Your own US ROM of Jet Force Gemini	Studio reads it to show the game’s levels, objects and models while you edit; the build reads the entries your pack copies.
JFG-Studio (Python 3.12)	The level and pack editor.
The decomp checkout	Studio uses its `tools/jfgformats` to read and write the game’s formats.
Jet Force Gemini: Recompiled	Studio’s Play button installs your pack there and starts the game in your level.
Blender 3.5+ (optional)	Modelling level geometry; the jfg64 add-on helps.
LLVM 18.1.8 and RecompModTool (optional)	Only for C code mods.

Installing JFG-Studio

JFG-Studio’s source is on GitHub: VibinToast/JFG-Studio .


git clone https://github.com/VibinToast/JFG-Studio.git
cd JFG-Studio
python -m venv .venv
.venv\Scripts\python -m pip install -e .[dev]
.venv\Scripts\python -m jfgstudio

On Windows, studio.bat does the last step for you. Then set the three paths in File › Settings… (or jfgstudio settings set <key> <path>):

Setting	Points at	Found automatically
`decomp`	The decomp checkout (with `tools/jfgformats`)	A `Decomp` folder next to JFG-Modding-Tools
`port`	The Jet Force Gemini: Recompiled folder	No
`rom`	Your US ROM (z64, v64 or n64 byte order)	`baserom.us.z64` or `jfg-us.z64` in the workspace

The first time Studio needs it, it builds a catalog from your ROM in your user data folder: the game’s levels, object types, models and planet map. It stays on your machine. Without it the Scene still opens your own geometry, but the Prefabs, Models and Kinds windows say “No catalog”.

Where things go

Path	What
`<port>/mods/`	Installed packs (`.nrm`)
`<port>/bin/jfg_mods.log`	The mods log
`<port>/bin/mod_ids.json`	Numbers the packs’ levels and content got (keep it)
`<port>/bin/saves/<save>_worlds.json`	Opened and completed pack planets, per save file
`<port>/bin/texture_packs/`	Folder texture packs
`<port>/bin/texture_dump/`	Dumped textures: the game’s, and `texture_dump/<mod id>/` for each pack’s own
`my_planet.jfgproj/`	A Studio project (format)
`my_planet.jfgproj/build/`	The pack Studio built

Open the example world to see a finished pack, or start your own with Your first planet.