Leon Ops: Zombies Kennedy

Resident Evil 4's Leon S. Kennedy in Call of Duty: Black Ops Zombies, played the RE4 way - now with online co-op for up to 4 players. A fan mod: you bring your own copies of both games, and the characters are built from your Resident Evil 4 on your own PC. Nothing from either game is in this repository or its releases.

• Co-op for up to 4 players, each as their own RE4 character (see Co-op)
• Four characters with their own perks: Leon, Ada, HUNK and Luis, each with their own voice, hits and death - press Switch Weapon at the start of a match to change (see Characters)
• Over-the-shoulder camera, RE4 tank controls (turning on the spot with RE4's own step-turn), RE4's quick 180 turn, and a sidestep while aiming
• Laser sight with RE4's own aim sway (from RE4's aiming code); standing still, the mouse swings the camera around Leon, and aiming turns him to where it looks
• RE4's HUD in place of Black Ops' ammo counter: the stone ring life meter (half a ring, the whole ring with Juggernog; green, then yellow, then red as you're hurt), your rounds and reserve inside it (red when low), and your character's name - all converted from your own Resident Evil 4
• RE4's animations for every kind of gun (handgun, Broken Butterfly, shotgun / Striker reloaded shell by shell, rifle, Chicago Typewriter, TMP, rocket launcher, the mine thrower for the wonder weapons), played with RE4's own motion code
• Knife slash and grenades the RE4 way; stagger a zombie with a head or leg shot (it glows faintly yellow), then roundhouse kick it - the staggered zombie always dies, and the others the kick catches die or get back up (Ada's kicks kill more often)
• Super Salvador in every Hellhound round: he comes out of the dogs' lightning shouting "¡Te voy a matar!" and chases you with the Mercenaries' chainsaw spin, its engine roaring - one touch of the saw downs you. Head and leg shots, the Thundergun and traps make him flinch (traps can't kill him); killing him gives 1000 points and a Fire Sale
• RE4's Merchant at the Mystery Box: "What're ya buyin'?", and a line for the weapon it gives you ("Stranger, stranger, now that's a weapon!" for the wonder weapons)
• Leon's hit reactions, death, pain grunts and voice
• Gamepad support with RE4's layout
• Boots straight to the zombies map list

Controls

	Keyboard / mouse	Gamepad
Walk / turn	W S / A D	Left stick
Run	Shift (press once)	Hold A, or press L3 once
Quick 180 turn	S + Shift	Back + A
Aim / fire	Right / left mouse	LT / RT
Sidestep (aimed)	A D	Left stick
Knife	Space	B or R3
Kick (staggered zombie), use, reload	F / R	X
Change character (start of a match)	Switch weapon	Switch weapon

Characters

Pick one with Switch Weapon during the first seconds of a match; the line under the prompt shows the perk.

	Perk
Leon	His head and leg shots stagger zombies far more easily, he takes one more hit (+50 health, on top of Juggernog's), and he is a 5% faster
Ada	15% back on everything she buys, a second chance at a power-up on each kill, and a wider, harder kick
HUNK	Aims, reloads, switches guns and readies grenades about 1.4x faster (Speed Cola still upgrades him)
Luis	25% more damage, and his grenades, launchers and explosive wonder weapons blast a wider area

Everyone moves 20% faster than Black Ops' own pace.

Play it

You need, on Windows, Call of Duty: Black Ops (Steam app 42700) and Resident Evil 4 (2005), Ultimate HD Edition (Steam app 254700). The base game has Kino der Toten and "Five"; the other zombie maps come with the Black Ops map packs.

The Resident Evil 4 HD Project works too (and so does the plain Ultimate HD Edition).

With Melty: get it from https://melty.gg/m/leon-zombies-kennedy and press Play. Melty installs it, builds the characters the first time and starts it.

Without Melty: download the latest LeonZombies-<version>.zip from Releases, unzip it anywhere and run LeonLauncher.exe. It finds both games in your Steam libraries (or asks for their folders once), builds the four characters from your Resident Evil 4 the first time (under a minute) and starts the game. Neither game's folder is changed.

Co-op

Up to 4 players, each on their own PC with their own copies of both games and Steam running. Everyone plays their own character - pick one with Switch Weapon at the start of the match - and sees the others' moves: their aim and laser sights, shots, reloads, knife, grenades, kicks, hits and voices. A downed teammate shows the revive icon; once you bleed out you spectate a teammate, and you're back in the next round.

With Melty (easiest): the host presses Play and starts a map. Friends open the mod's Melty page and press Join: Melty starts their game and puts them straight into the host's match. Melty relays the connection, so nobody forwards ports or types addresses. The first time you host, Windows may ask to let BO1Zombies.exe through its firewall - allow it.

Without Melty: the host starts a map from LeonLauncher.exe. Friends start theirs, open the console (~) and type /connect <host's IP address>:3074 (with the slash). On the same network that's the host's local address (e.g. 192.168.1.20). Over the internet the host needs UDP port 3074 forwarded to their PC - or everyone joins the same virtual LAN (ZeroTier, Tailscale, Radmin VPN...) and uses the host's address on it.

Joining a match already under way works: you spawn next to your team.

How it works

BO1Zombies.exe is the Black Ops engine rebuilt from a decompilation, with this mod's changes. It runs from its own folder and reads your Black Ops install (BO1Z_GAME_DIR). The mod lives in mods/leon (scripts) and the engine (src/gfx_d3d/r_runtime_xmodel.cpp builds Leon's model at level load; src/cgame_mp, src/client_mp and src/bgame hold the camera, controls, aiming and animation code). tools/leon-converter turns the characters' and Super Salvador's models, textures, motions and voices from your Resident Evil 4 into mods/leon/rtmodels/*.rlm and mods/leon/sound, and RE4's HUD images into mods/leon/rtmodels/re4hud.rlh (drawn by src/cgame_mp/cg_re4hud_mp.cpp). Super Salvador is an RE4 model carried by a hidden zombie (mods/leon/maps/leon/_salvador.gsc, _rtenemy.gsc).

Co-op is Black Ops' own network game: the host's game is a listen server and friends connect to it. A joining PC compiles the level's scripts itself so its zombies' animations match the host's, every player's character is set by the server's scripts (mods/leon/maps/leon/_character.gsc), and another player's RE4 actions are rebuilt on each screen from what the network sends about him (src/cgame_mp/cg_pose_mp.cpp: RtRemoteActions). With Melty, the game reads the friend's address to join from %LOCALAPPDATA%\LeonZombiesKennedy\melty.properties and writes the address it hosts on to melty.log there (src/qcommon/common.cpp); Melty carries the connection between them. tools/leon-launcher is the launcher, tools/melty and melty.json the release package and Melty's install recipe.

Build from source

1. Build the engine (Visual Studio 2022, 32-bit): cmake -B build -A Win32, then cmake --build build --config Release --target BO1Zombies copy_mods.
2. Build the converter's two native pieces (tools/leon-converter/README.md): lfsunpack.exe (with libmspack) and the RE4 decomp's motion host.
3. python -m venv build\melty\venv, build\melty\venv\Scripts\pip install pyinstaller pillow, then powershell -File tools\melty\build_leon_package.ps1 -Version <version> writes build\melty\LeonZombies-<version>.zip.

Not included here, though the decompilation project ships them: Valve's Steam client DLLs (the exe needs only the SDK's steam_api.dll), and the retail-derived files of its mods/_stack and mods/zinfo examples (copies of Treyarch's maps/_zombiemode_ffotd.gsc and entity placements from the retail maps). The Leon mod needs none of them; those two example mods do (tools/leon-publish/publish_public.sh filters them out of this repository).

Credits

• Black Ops engine: MisaDev4/bo1-zombies-decompiled, the decompiled engine code for Black Ops 1 Zombies this project is built on.
• Resident Evil 4 GameCube decompilation: adonis-singh/re4, whose motion code plays RE4's animations on Leon exactly as the game does.
• Resident Evil 4 UHD tools: JADERLINK's RE4-UHD-PACK-TOOL and RE4-UHD-BIN-TPL-TOOLS (MIT), the reference for the UHD texture packs and model files.
• RE4 .lfs archives: emoose's re4-research (the format) and libmspack (LGPL 2.1, its LZX decoder).
• Resident Evil 4 and Leon S. Kennedy © Capcom. Call of Duty: Black Ops © Activision. A fan project, not affiliated with or endorsed by either.

License

The project's own work is MIT (LICENSE); the decompiled engine, the credited projects and both games keep their own terms.