openranch

An open source rewrite of the engine and game logic of Slime Rancher (Monomi Park, 2017), built with Godot 4.7 and C#. It plays the game using the models, textures, sounds and text from your own copy of Slime Rancher, which the importer reads on your PC. Nothing from the game is in this repository, and nothing from the game is ever committed.

You need a legal copy of Slime Rancher (the Steam release, 1.4.x) to use openranch.

openranch is not affiliated with or endorsed by Monomi Park.

Roadmap

The goal is all of Slime Rancher playable 1:1 from your own install. Milestones are weighted by size; overall 54%.

	Milestone	Weight	Done
M0	Foundation: Unity readers, importer, v12 save reader	5	100%
M1	Walk The Ranch: world, collision, zone lighting	8	88%
M2	Core loop: slimes eat and make plorts, vacpack, corrals, plort market	8	88%
M3	Ranch save: full load, save back, running day cycle	6	100%
M4	Every zone walkable, streamed as one world, teleporters	18	67%
M5	Every slime, largo, gordo and tarr; feral; food, crops and chickens	15	67%
M6	Ranch economy: plots and upgrades, expansions, Lab, Exchange, 7Zee	15	40%
M7	Game flow and UI: menus, HUD, vacpack UI, Slimepedia, mail, options, save slots	10	0%
M8	Sound and look: music, sound effects, clean-room landscape, foliage, water, sky	8	13%
M9	Story and completion: Ogden, Mochi, Viktor, Slimeulations, achievements, ending	7	0%

Want to help? See CONTRIBUTING.md.

Status

Milestone 0, the foundation, is done:

• openranch-import inventory reads the game's 11 Unity data files (Unity 2019.4.29f1) and counts every asset by type.
• openranch-import saves --verify reads your saves and re-writes each supported one in memory to prove the reader understands every byte. All 15 version-12 saves on the development PC re-write byte for byte. Saves from before game 1.4 (versions 8 and 9) are listed but not read yet.
• The Godot project starts and lists the ranches it found.

Milestone 1, walking around The Ranch, is in progress:

• The world scene is read straight from your install: The Ranch's 7,241 objects become 4,636 rendered instances (static batches, multimeshes) and 2,291 collision shapes in about 2 seconds.
• Crunched textures (Unity's DXT1/DXT5 "crunch" format) are decoded by a C# port of crunch's decoder; everything else goes to the GPU as stored.
• A first-person controller with a jetpack uses the original player's capsule size and slope limit.
• --collision-check drops the player across the area's ground and checks it lands every time (40 of 40).
• Objects the game switches on and off at runtime follow the same rules: ranch upgrades by progress, night-only decorations by the hour, gadget-site markers by gadget mode. --save FILE shows the world as in one of your saves (read only).
• Sky, fog, ambient light and the sun follow the original's zone settings and time of day, including cave lighting. Fog is drawn with the original's formula in a full-screen pass.
• Reference check: screenshots from 5 fixed spots (home deck, corrals, overgrowth, grotto, docks) line up with the original game's view of the same spots. Colours still differ in places (ranch palette recolouring, landscape detail textures, clouds).
• Script data: every one of the game's 37,299 script components (758 script types, from slime diets to zone ambience) reads cleanly, with layouts worked out at runtime from the game's own assemblies through metadata. No game code is loaded or run. openranch-import scripts --dump SlimeDefinition shows an example.

Milestone 2, vacpack and slimes, works in The Ranch: Pink, Tabby and Rock slimes (built from the game's own item templates) hop, eat and make plorts; the vacpack has 4 slots to suck up and shoot items; corral walls keep slimes in; the plort market buys plorts at the price read from your copy. --m2-check runs it headless: a Pink slime eats a carrot, its plort is vacuumed up and sold, and a Rock slime thrown at the corral wall stays in. The rules underneath, headless:

• src/OpenRanch.Simulation holds slime hunger and eating, the 4-slot vacpack and the plort market with saturation, as plain .NET. Diets, favorites, plorts, eating tuning and market prices are read from your install (SlimeData, MarketData); the rules are in docs/behavior/.
• A test feeds a Pink slime a carrot, vacuums up its plort and sells it at the price read from your copy.

Sound and text: openranch-import sounds reads all 953 of the game's sound clips and converts them (FMOD banks to Ogg/WAV, in memory or exported to a folder outside the repo), and openranch-import text reads its 101 text bundles in every language. Formats are in docs/formats/audio.md and text.md.

The full plan, with milestones M0 to M5, is in the project's rewrite plan document.

Layout

Folder	What it holds
src/OpenRanch.Formats	Readers for Unity serialized files and Slime Rancher saves, plain .NET 8, tested without Godot
src/OpenRanch.Simulation	Game rules (slimes, vacpack, plort market), plain .NET 8, no engine dependency
src/OpenRanch.Importer	The openranch-import command
game/	The Godot 4.7 project (C#)
tests/	Unit tests, plus tests that run against your install when it is present
docs/	Format notes and clean-room behavior notes, written in our own words
tools/	The commit guard, low-priority runner, and off-screen capture and headless check scripts

Building

You need the .NET 8 SDK. Godot 4.7.2 (.NET build) is needed to run the game project.

dotnet build OpenRanch.sln
dotnet test OpenRanch.sln
dotnet run --project src/OpenRanch.Importer -- inventory
dotnet run --project src/OpenRanch.Importer -- saves --verify

Run the game from the Godot editor (open game/project.godot), or from the command line:

godot --path game -- --scene ranch

Scripted runs never take focus: tools/godot-capture.ps1 renders a screenshot in an off-screen window, and tools/godot-headless.ps1 runs checks such as --collision-check with no window.

The game is found through the OPENRANCH_GAME_DIR environment variable or your Steam libraries. On a shared PC, tools/run-low.ps1 runs any of these at below-normal CPU priority, for example powershell -File tools/run-low.ps1 dotnet test OpenRanch.sln /m:2.

Keeping game data out

The repository holds only new code and notes. Please enable the commit guard once after cloning:

git config core.hooksPath .githooks

tools/check_no_game_files.py blocks Unity asset files, sound banks, saves, the game's DLLs and anything that looks like decompiled game code. CI runs the same check on every push.

The rewrite is clean-room: the original's behavior is studied on a developer's own PC and written down in plain words under docs/, and new code is written from those notes. Decompiled code is never copied into this repository.

License

GPL-3.0. See LICENSE.

Third-party code

src/OpenRanch.Formats/Unity/Crunch.cs is an altered version of the crunch texture decoder (Copyright (c) 2010-2016 Richard Geldreich, Jr. and Binomial LLC), translated to C#. It keeps the original ZLIB license notice at the top of the file.

Sound banks are read with Fmod5Sharp (MIT license), a NuGet dependency of OpenRanch.Formats.