OpenMCM2

OpenMCM2

An open-source engine for Motocross Madness 2 (Rainbow Studios, 2000), rebuilt from scratch in Rust from a study of the original game. It runs natively on macOS (Metal), Windows (DX12/Vulkan) and Linux (Vulkan).

Built with AI. OpenMCM2 is entirely vibe coded: one fan directing Claude Code (Anthropic's AI coding agent), which did the reverse engineering, wrote the code and docs, and checked the result against the original game. Every line was written by AI under human direction and testing. Bug reports, reviews and human contributions are very welcome.

This repository contains no game files. Like OpenMW, the engine reads the tracks, models, textures, sounds and menus from a copy of the game that you own. Point it at the folder of your install (or the CD's GAME folder).

Project page: https://crspytopgn.github.io/openmcm2/

Watch the showcase video: https://youtu.be/rP0TEnWLzNo

Playing

Download a release and start OpenMCM2 (OpenMCM2.app on a Mac, mm2-launcher on Windows and Linux). The first time, point it at your own copy of Motocross Madness 2: a CD image (.iso, .bin/.cue, .img, .mdf, .nrg), the CD itself, or the folder it is installed in. It copies the game's GAME folder into the port's user folder (~/Library/Application Support/MM2/GAME on a Mac, %APPDATA%\MM2\GAME on Windows, ~/.local/share/mm2/GAME on Linux). Then pick the look, effects, full screen, window size and vsync, and press Play. The game itself is never downloaded: OpenMCM2 ships without any game data.

More tracks. The launcher's Get tracks section lists the player-made tracks on MDX Racing and, only for the ones you pick, downloads the zip from there and adds its track to the game (tracks.ini in the user folder records them, so Remove takes them out; a track never replaces a file it didn't add). Tracks only offered as .rar link to the site instead.

The game can also be started directly with its folder, from a terminal:

./mm2-viewer "/path/to/Motocross Madness 2"

Started with no folder, mm2-viewer uses the launcher's copy of the game (or a game folder it is run from). mm2-launcher --import <image or folder> does the setup without a window. To build it yourself, install Rust from https://rustup.rs, then:

cargo build --release -p mm2-viewer -p mm2-launcher
./target/release/mm2-launcher

On a Mac, sh tools/make-mac-app.sh builds target/release/OpenMCM2.app.

It opens the original front end: profiles, the main menu, single player and its event screens, Bike & Rider, options, the Pro Circuit career, replays and network races between copies of OpenMCM2. Every event the original has is in: Supercross and National races, Baja and Enduro gate races, the Stunt Quarry, Moto-Tag, ghost races and replays. Given a track .ENV instead of the game folder, it starts a race on that track straight away.

Keys are the profile's own map (the original's factory keyboard by default): Up/Down gas and brake, Left/Right steer, W/S lean, Z/X stunts, Enter Kahuna, Space taunt, LShift Thrill Cam, LAlt Reverse Cam, LCtrl clutch, Backspace back up. In a race Numpad5 (or C) cycles the camera views, Home/End zoom, F5 to F10 switch the stats, radar, gauges, sky, particles and shadows, [ ] or PgUp/PgDn watch the other riders. In network races / opens chat. Alt+Enter (Option+Return on a Mac) switches full screen.

Controllers. Xbox and PlayStation pads and flight sticks work, as the original's DirectInput joystick did: the X axis steers, the Y axis leans, buttons 1 and 2 are gas and brake, 3 and 4 the stunts, and on a pad the right and left triggers are gas and brake too. Options > Controls binds the pad's or stick's buttons to any action, and Accelerate also takes a flight stick's throttle lever. The Controls page names the pad in use and shows its own button names (Xbox A/B/LB/RT, PlayStation Cross/Circle/L1/R2), and the stick can be bound to steer or lean. The pad also works the menus: the stick or D-pad moves the pointer, A clicks and B goes back. With several plugged in, the one last touched rides.

Optional extras, off unless asked for:

• --enhanced draws a gently remastered look (sun shadows, HDR, ambient occlusion, detailed ground, dust, widescreen race display). F3 switches between it and the original look while racing; the riding is the same either way. See docs/enhanced-graphics.md.
• --hires <pack> uses a high-resolution texture pack that you make yourself from your own copy of the game. See docs/hires-textures.md. Packs are never shared here.

On Linux, building needs ALSA and libudev headers (sudo apt install libasound2-dev libudev-dev pkg-config); build with --no-default-features to leave gamepad support out.

How close it is

The player's bike runs the game's full player model from crates/mm2-physics (rigid body, two tyres on shocks, engine and gears, crash rules, tricks), stepped once per frame as the original does. The computer riders run the game's own AI model and controller. The riding is checked against recordings of the original game: most comparison runs match it (crash outcome, speed and pitch), but some jump landings, rough ground and knife-edge object clips still differ, and the computer riders crash a little more and do fewer tricks than the original's. The notes are in docs/physics.md.

Formats

Format	Used by	Status
RS2 archive	RES/ENGINE.RES, RES/*.TEX, UI/*.DAT	Reads and extracts
FAOE container	other RES/*.RES, TERAFORM/**/*.ENV	Decodes (RS2 behind a byte cipher keyed by file name)
LZW streams	inside .trn and other files	Decodes
.trn terrain	each track .ENV	Heightmap, normals, textures and texture tiles
.scn scene	each track .ENV	Start position, lights, fog, models, sounds
.slb model	RES/MODELS.RES, RES/BIKE.RES	Frames, materials, LODs, meshes
model textures	RES/OBJECTS.RES, RES/*.TEX	RGB555 (magenta = transparent) and ARGB4444 with mips
.mcf / .mot	RES/OBJECTS.RES, RES/BIKE.RES	Animated models and their motions
.mbf rider morphs	RES/BIKE.RES	Corrective shapes for elbows, hips and so on
.col collision	RES/COLSEG.RES	Solid objects
.tdf track definition	each track .ENV	Course, start and finish lines, gates
.pb presets	UI/UIRES.RES	Bikes, riders, presets
.dtm UI	UI/*.DAT	The original menus
procedural .vue paths	RES/PROCVUE.RES	Trains and other traffic that follow a path
Indeo 5 video	UI/*.AVI	The intro and credits movies

Tools

cargo run -p mm2-tools -- info  /path/to/GAME/RES/*.RES
cargo run -p mm2-tools -- list  /path/to/GAME/RES/ENGINE.RES
cargo run -p mm2-tools -- extract /path/to/GAME/RES/BIKE.RES extracted/bike
cargo run -p mm2-tools -- terrain /path/to/GAME/TERAFORM/SX/SX01.ENV sx01-terrain
cargo run -p mm2-tools -- model extracted/bike/Yamaha.slb

Tests

cargo test runs without any game files. To also check every archive, track, model and texture of your install, set MM2_DATA to the game folder:

MM2_DATA="/path/to/Motocross Madness 2" cargo test

Credits

• The Indeo 5 decoder in crates/mm2-indeo is a port of FFmpeg's, by Maxim Poliakovski, and keeps FFmpeg's licence (below).
• Ground materials for --enhanced are from ambientCG, CC0.

Supporting the project

OpenMCM2 is free and always will be. If you enjoy it and want to chip in, you can sponsor it on GitHub.

Legal

OpenMCM2 is an independent fan project. It is not affiliated with, endorsed by or sponsored by Microsoft or Rainbow Studios. Motocross Madness is a trademark of Microsoft Corporation, and the game, its data and artwork are © Microsoft. This repository contains no game files and no code from the original game: it is a new implementation, and you need your own legitimately obtained copy of Motocross Madness 2 to use it. Do not commit game files, extracted assets or texture packs made from them.

Licence

Licensed under either of the Apache License, Version 2.0 or the MIT licence, at your option, except crates/mm2-indeo, which is under the GNU LGPL 2.1 or later (COPYING.LGPLv2.1). The full source of every release is here, so release builds can always be rebuilt with a changed copy of that crate. Unless you state otherwise, any contribution you submit is dual licensed as above.