Resident Evil 1 for PC Decompilation

Introduction

This is a decompilation Resident Evil 1 for PC released in 1997. The original game code, reverse-engineered from the Ghidra decompilation of the 1997 executable, is rebuilt on a modern rendering layer, for two platforms:

Platform	Renderer	Audio	FMV
Windows (Win32)	Direct3D 11	XAudio2	MCI
Linux (SDL2 + OpenGL 3.3)	OpenGL core	SDL2 mixer	ffmpeg (Cinepak AVI)

Both builds share every line of game logic; only the platform layer and the renderer backend differ (src/marni/MarniDX.cpp vs MarniDX_GL.cpp, src/platform/win32/ vs src/platform/linux/). The GL backend is written against the GLES-3-compatible subset so the same code can be repointed at Android/Switch later.

The port is functional-complete: the entire original game is playable — every room, enemy, cutscene, FMV, menu and ending. Extensive playtesting confirms it behaves like the original release.

The DirectX 5.0 wrapper of the original (Capcom's Marni System, built on DirectDraw/DirectSound) is re-implemented on top of those backends (src/marni/)

Completion status

Measured against the Ghidra project: 2393 functions in the original binary (+161 DLL imports provided by the loader). Every function has been triaged:

Stream	Count	Status
Game logic implemented in src\	1716 of 1717	done
Marni System DirectX internals → DX11 / OpenGL backends	84 of 84	done
CRT / MSVC runtime (provided by toolchain)	290	out of scope
Compiler SEH / static-init glue (absorbed by real C++ ctors/dtors)	177	out of scope
Raw D3D5 API paths (replaced by MarniDX)	108	out of scope
Software-FMV shared-memory player (replaced by MCI / ffmpeg)	11	out of scope
Import thunks (loader-provided)	6	out of scope

How to build

Windows

Requirements: - Windows - Visual Studio with C++ toolset and MSBuild (Game.sln, Win32 platform)

Build:

build.bat

This invokes MSBuild on Game.sln (Release / Win32) and produces bin\Release\residentevil.exe. For a Debug build use:

build_debug.bat

This produces bin\Debug\residentevil.exe.

Both scripts find MSBuild with vswhere.exe, so any Visual Studio edition and version (2017 or newer) works without editing a path. The solution itself pins PlatformToolset=v145 / SDK 10.0.26100.0; on an older installation override them with the RE1_TOOLSET and RE1_SDK environment variables, e.g.

set RE1_TOOLSET=v143
set RE1_SDK=10.0
build.bat

Note: Release intentionally builds with WholeProgramOptimization disabled — /GL+/LTCG miscompiles the task scheduler's naked-assembly stack switching (cross-TU inlining assumes standard prologues), which caused intermittent crashes at room load. Don't re-enable it.

Note: never call raw OutputDebugStringA from code that can run inside a scheduler task — without a debugger it fail-fasts the process (0xC0000409) because the exception cannot be dispatched on the task's switched stack. Use dbg_printf / dbg_safe_str (src/DebugPrint.h), which are gated on IsDebuggerPresent.

To build from a developer command prompt instead:

msbuild Game.sln /p:Configuration=Release /p:Platform=Win32 /t:Build

Linux

A native 32-bit binary (-m32) built with CMake. The game logic and the Marni layer are shared with Windows; the platform layer, the OpenGL backend and the ffmpeg FMV decoder are Linux-only files (src/platform/linux/, src/marni/MarniDX_GL.cpp).

Requirements (64-bit host building 32-bit).

Debian/Ubuntu:

sudo dpkg --add-architecture i386
sudo apt update
sudo apt install build-essential cmake g++-multilib libc6-dev-i386 \
                 libsdl2-dev:i386 \
                 libavformat-dev:i386 libavcodec-dev:i386 \
                 libavutil-dev:i386 libswresample-dev:i386

On Ubuntu 24.04 (noble) libsdl2-dev:i386 cannot be resolved: it pulls libpulse-dev:i386 and libibus-1.0-dev:i386, whose libglib2.0-dev:i386 dependency has no i386 build there (the glib dev utilities are amd64-only). None of those headers are used, so install the rest and force the SDL2 dev package past its dependency check:

sudo apt install -y --no-install-recommends libgl-dev libsdl2-2.0-0:i386 \
     libavformat-dev:i386 libavcodec-dev:i386 \
     libavutil-dev:i386 libswresample-dev:i386
cd /tmp && apt-get download libsdl2-dev:i386
sudo dpkg -i --force-depends --force-overwrite libsdl2-dev_*_i386.deb

Arch/CachyOS (with [multilib] enabled in /etc/pacman.conf):

sudo pacman -S --needed base-devel cmake lib32-glibc lib32-gcc-libs \
                        sdl2 lib32-sdl2 ffmpeg lib32-ffmpeg lib32-mesa

The 32-bit packages are the point: the target is 32-bit. On Arch the lib32-* packages ship runtime objects only, so the ordinary sdl2/ffmpeg packages supply the headers, and lib32-mesa is the GL driver SDL loads when it creates the context. The build finds the 32-bit library directory itself (Debian /usr/lib/i386-linux-gnu, Arch /usr/lib32) and links the sonames actually installed, so the same tree configures on both — no pkg-config path or other environment needed.

Note that the result is dynamically linked against the host's ffmpeg ABI (ffmpeg 6 = libavcodec.so.60 on Ubuntu 24.04, ffmpeg 9 = .so.62 on Arch): build on the distribution you intend to run on.

Build:

cmake -S . -B build/linux -DCMAKE_BUILD_TYPE=Release
cmake --build build/linux -j

This produces build/linux/residentevil, which can be launched from anywhere — assets and saves are resolved from the binary's directory plus config.ini, not from the working directory:

./build/linux/residentevil

Diagnostics go to stderr; RE1_DEBUGLOG=1 also appends them to re1_debug.log. A fatal signal writes a symbolized crash.log. Test hooks: --capture <file> [frames] dumps the back buffer and exits, --press <scancode> <frame> [hold] injects a synthetic key press, which together can drive an attract-demo run headlessly.

For the sanitizer build (ASan/UBSan) and the rest of the porting notes see docs/LINUX_PORT.md.

Packaging a portable bundle

build/linux/residentevil is linked against the build host's ffmpeg, so it only runs where those exact sonames exist. To run it on another distribution, whose rootfs is read-only and whose package repo is frozen — build a bundle:

bash tools/package_linux.sh            # --with-assets also copies assets/

dist/residentevil-<version>-linux-x86/ then holds the binary, a launcher that puts lib/ on LD_LIBRARY_PATH, the initial config.ini (from config.ini.template) and the bundled 32-bit libraries. Only the glibc family and the GL driver stack (libGL/libEGL/libdrm/libgbm/ libvulkan) stay the host's, because they have to match the running kernel and GPU — on Arch/CachyOS that means lib32-mesa, which SteamOS and any 32-bit-capable desktop already have. Everything else travels, including the X11/Wayland and ALSA/PulseAudio clients, so the bundle does not depend on the target's 32-bit package set.

Game data is not included, same as the Windows release — migrate your own copy into place with the asset migrator and put the USA/ (and optionally JPN/, and the Director's Cut DC/) trees next to the launcher.

Installation

Getting the game data into place - which releases are supported, the asset migrator, the folder layout, config.ini and choosing the USA / JPN release - is covered in INSTALLATION.md.

Features

WebP backgrounds and HD textures

The port has an HD mode: high-resolution backgrounds, textures, model skins, movies and fonts, all optional and all read from files. With no HD/ folder the game looks exactly as the original. Everything below is read as WebP (lossy or lossless, any resolution) unless noted:

• Room backgrounds. A Stage<n>/RC*.webp file is used in place of the .pak of the same name. The asset migrator can write a whole tree that way (Room backgrounds option: lossless is the same picture about 20 % smaller), and a hand-made high-resolution background is installed the same way.
• HD textures. Any other texture - models, items, menus, fonts, room masks
• can be replaced by dropping <hash>.webp into an HD/ folder beside USA/ (or into a sub-folder of it, to group a pack by type). Set DumpTextures=1 to have the game write the originals, named by that hash, to HD/dump/.
• Model skins. A character or enemy skin can also be named after its model, HD/<TREE>/ENEMY/EM1010.webp (TREE = the folder the model was read from).
• HD movies. HD/USA/MOVIE/OU.mp4 is played ahead of the tree's own .mp4 / .avi.
• HD fonts. Text is drawn in real TrueType fonts instead of the bitmap sheets: Archivo Black for the title menu, Archivo Narrow for the 8x8 text and Libertinus Serif / M PLUS 2 for the in-game messages, item names and files (HD/<USA|JPN>/Data/TITLEFNT.TTF, FONTUS.TTF / FONT.TTF, FONTUS_14.TTF / FONT_14.TTF). The asset migrator's HD Pack tab installs them; the fonts are under the SIL OFL 1.1.

[Textures]
HdTextures=1     ; use HD/<hash>.webp replacements (default; free with no HD/ folder)
DumpTextures=0   ; 1 = write every texture to HD/dump/<hash>.png

docs/HD_TEXTURES.md explains how to make a pack and what its limits are. The asset migrator's HD Pack tab imports the Seamless HD Project pack format (made for Classic REbirth) into HD/, grouped by texture type: backgrounds and masks from a built-in table, model skins under the model's name, the Seamless HD Project movies, and the rest by matching against the game's own texture dump. Set HdTextures=0 or in the game settings menu to switch all of HD mode off without removing the folder.

Options menu (title screen)

The title menu is NEW GAME / LOAD GAME / EXTRA / OPTIONS in every mode (EXTRA appears only while the Battle Game is offered). OPTIONS opens a menu of its own with four pages, so none of the settings below need a text editor:

Page	What it holds
DISPLAY	Window mode (windowed / borderless fullscreen), resolution, vsync. The picture always stays 4:3: a widescreen monitor or window size gets black bars instead of a stretched image. Resolution is the window's size; fullscreen uses the desktop's.
INPUT	Every control, for the keyboard and for the gamepad: select a cell and press the new key or button. Each device has a reset row. The arrow keys, Enter and Esc always work in this menu, whatever is bound.
GAME	Game mode, region, PS1 ending credits, PS1 FMV subtitles, skip any FMV, Battle Game, western difficulty - the [Game] keys and [Assets] Version described in the sections below. An entry whose assets are not installed cannot be selected.
BONUS	The outfit each playable character wears, with the model shown beside the list, and an on/off switch for each bonus weapon you have unlocked. Moving onto a weapon row shows its owner aiming it: Chris with the rocket launcher and the Minimi, Jill with the Colt Python and the Ingram.

Game mode and region are read once at start-up, so changing either needs a restart: APPLY AND RESTART on the GAME page does it for you, and leaving the menu without it keeps the change for the next start.

Bonuses are kept in bonus.dat in the save folder, across every save and every mode:

Bonus	How it is unlocked
Alternate outfit (Chris, Jill)	getting the special key, in any mode
PC outfit (Chris, Jill)	getting the special key in the original mode
Director's Cut outfit (Chris, Jill, Rebecca)	clearing the Director's Cut's ADVANCED (arrange) game
Saturn outfit (Chris, Jill)	getting the special key in Saturn mode
Rocket launcher	earning it at the ending, in any mode
Colt Python	the ADVANCED best ending of the Director's Cut
Ingram (Jill) / Minimi (Chris)	earning it at the ending in the original mode

An outfit other than DEFAULT is worn in every mode, in the campaign and in the Battle Game, and takes priority over the wardrobe. A bonus weapon that is switched on is put in the item box when a new game of the campaign starts; the Battle Game never uses the bonus weapons (nor the Colt Python's infinite ammo). The Director's Cut and Saturn outfits need those releases migrated (see Asset migration).

The menu needs the title font, Data/TITLEFNT.BIN, which the asset migrator's PC tab writes; without it the title keeps the art the release shipped with and has no OPTIONS item.

Options menu (in game)

The button that opened the original options screen ("A" key) now opens the same menu in game, cut down to DISPLAY, INPUT, BACK TO TITLE (asks for confirmation; unsaved progress is lost) and BACK (Esc / cancel does the same) to return to the game. The pages are the title menu's, so a rebinding made here applies at once. The room's music keeps playing underneath.

Director's Cut mode

[Game] Mode in config.ini picks which release's content runs. It is a single key that selects both the code branches and the asset overlay folder, so the two can never disagree:

[Game]
; OG = the PC release (default); DC = the PS1 Director's Cut overlay
Mode=DC

DC is an overlay, not a second full tree: DC/ beside USA/ and JPN/ holds only the files the Director's Cut changes or adds, laid out like a base tree. ResolveAssetRoot (src/system/AssetPath.cpp) probes it first and falls through to the base tree for the folders the DC disc genuinely cannot supply, so the base trees stay complete and pristine and several releases can share one install. Build the overlay with the Director's Cut tab of the asset migrator; the full design is in docs/DC_PORT.md.

PS1 ending credits

The PC release plays its credits as movies with the text baked into the picture (stfc_r, stfj_r, stfz_r, staf_r). The PS1 versions draw them live instead, and the port can do the same, following PS1 ENDING.EXE:

• Endings 1-3 (staff roll): the STAFF2.STF credit strips scroll up over a black screen, with the movie playing as music only. The last strips are the RESIDENT EVIL logo, which fades out with the rest.
• Endings 4-7 (cast roll): the character's movie (STFC for Chris, STFJ for Jill) plays in shots that fade in and out. The STAFF.STF name panels appear beside it, a black wipe covers part of one shot, and the roll ends on the zoomed BIO.TIM logo.

Director's Cut mode turns it on automatically. In OG mode, turn it on in config.ini:

[Game]
; 1 = draw the PS1 credits over the ending movies (DC mode is always on)
Ps1EndingCredits=1

It needs these files in the active tree (the DC/ overlay, or USA/ / JPN/ in OG mode):

File	Holds
Data/STAFF.STF	the cast-roll name panels (endings 4-7)
Data/STAFF2.STF	the staff-roll strips (endings 1-3)
Data/BIO.TIM	the RESIDENT EVIL logo
Movie/STFC.mp4, Movie/STFJ.mp4	the PS1 movies, which have no text in them

The Director's Cut tab of the asset migrator already writes all of these into DC/. For OG mode, tick Add PS1 assets from a PS1 disc image on the PC Assets tab and point it at a PS1 disc (the 1996 release or the Director's Cut). Use a raw .bin/.cue image so the movies keep their CD-XA audio. If the .STF files are missing, the ending plays the PC credit movie as before.

Skippable FMVs

Each movie carries its own skip mask in the original's FMV table (0x004c39dc, src/video/VideoPlayback.cpp): 0x0fff for the cutscenes and the Capcom/Virgin logos, 0x0000 — unskippable — for the endings (ED1-ED8, EU4/EU5), the PC credit movies (stf*_r) and DMF / DME. A single config key lifts that:

[Game]
; 1 = let every FMV be skipped, including the ones the original locks
SkipUnskippableFmv=1

It is off by default, so the shipped behaviour is the original's masks. The original's 100-frame grace period still applies, so a press during the first few seconds of a movie is ignored.

Battle Game (Saturn mode)

Sega Saturn mode carries a second game mode the other releases never had: the Battle Game, a fixed 15-arena run through STAGE8 with a preset loadout, scored on the ammo you did not spend. It is reached from the title menu's EXTRA item.

The Saturn unlocks that item with any ending, or with a port-2 X + Y + Z + Start code on the press-start screen. The code is not ported there is no second controller — so if you would rather not clear a game first, force it on:

[Game]
Mode=SATURN
; 1 = offer the BATTLE GAME item without having cleared a game
BattleGame=1

It is off by default and only does anything with Mode=SATURN. It is a read-time override: it never writes the unlock into a save, so a game finished with it on still records only what you actually earned. Clearing the game once also unlocks it for real, permanently, in that save.

Status: the entry into a run is ported — the item, the loadout and the first arena's art all work. The arena sequence itself is not finished, so a run ends at the first arena. See docs/SATURN_PORT.md.

Controls

The port keeps the original 1997 input model: every binding is a function (action, cancel, aim, inventory, options), and both the keyboard and the pad are remapped onto the same PS1 button word before the game logic sees them (JoyToPSX, src/game/InputSystem.cpp). Both devices are always live and can be used interchangeably.

Keyboard (default layout)

The original "Key Def" defaults, unchanged (g_keyBindingData, src/Globals.cpp):

Key	Function
Arrow Up / Down	Walk forward / backward
Arrow Left / Right	Turn left / right
C, Enter, Space	Action / confirm (open, examine, fire while aiming)
V, Ctrl	Cancel / run (hold while moving to run)
Esc	Cancel / back
X	Aim — hold to ready the weapon, then press the action key to fire
Z	Inventory / status screen
A	Options screen

Game pad

Every backend publishes into the same joystick slot, so the game cannot tell them apart:

• XInput (Xbox pads and anything exposing an XInput device) — preferred on Windows, brought up first (src/marni/MarniXInput.cpp).
• WinMM / HID — the original 1997 joystick path, used on Windows when no XInput pad is present (e.g. a DualShock 4 plugged in directly, or an old SideWinder).
• SDL_GameController — the Linux backend (src/platform/linux/input.cpp); the standard SDL mapping covers Xbox, DualShock/DualSense and Switch Pro pads.

The original joystick defaults had no OPTIONS binding at all, so the port installs a usable layout out of the box (InstallPadDefaultBindings). It only ever replaces a table that is still empty or byte-identical to the 1997 default — anything configured in the options screen is left untouched.

XInput / SDL	WinMM / HID (DualShock naming)	Function
Left stick / D-pad	Left stick / D-pad / POV hat	Move and turn
A	Cross	Action / confirm
B	Circle	Cancel / run
X, LB, RB, RT	Square, L1, R1, R2	Aim
Y, Start	Triangle, Options	Inventory / status screen
LT	L2	Run
Back	Share	Options screen

A pad may be plugged in or unplugged at any time; the XInput backend rescans on a throttle and takes over slot 0 when a pad appears.

Rebinding

Both layouts are editable from the INPUT page of the title screen's OPTIONS menu and from the in-game options menu (see Options menu above). Bindings are saved to config.ini. The original in-game screen ("Key Def" / "Joy Def", with its four direction-mapping presets, src/game/OptionsMenu.cpp) is no longer reachable.

As in the original, a save file carries the bindings it was made with, and loading it restores them - so loading a save made before a rebind brings the old layout back until you save again.

System keys

Key	Action
F9	In game: return to title screen (press again to confirm). At the title: exit the game (press again to confirm). Debounced, and blocked during FMV playback.
Print Screen	Save the current frame as a timestamped .BMP next to the game (original behaviour; skipped when the target drive has under 1 MB free).

Debug keys (port addition)

Compiled into both configurations but gated at runtime on [Debug] EnableDebug in config.ini (default: on in Debug builds, off in Release):

Key	Action
F1, or pad L1+R1 together	Open / close the debug menu: room change, inventory editor, flag editor, quick access (save / load / item box). Freezes gameplay underneath. Navigate with the arrows / Enter / Esc, or with the pad's bound action, cancel, aim and direction functions.
F6	Texture viewer overlay. Arrows select a page, hold A + arrows to pan, R resets the pan, F6 or Esc closes.
F8	Toggle the collision boundary overlay.

The debug menu's open/close pad combo is the one input read from raw hardware rather than through the remap table — L1+R1 are buttons 5 and 6 in the XInput, WinMM and SDL orderings, so the combo means the same thing on every backend.

Project layout

• src/marni/ — the Marni System compatibility layer; MarniDX.h is the backend interface, implemented by MarniDX.cpp (DX11/XAudio2, Windows) and MarniDX_GL.cpp (OpenGL, Linux). Both replace DirectDraw/DirectSound/D3D5.
• src/game/ — decompiled game logic (rooms, entities, menus, door system, TMD renderer, effects, screens), one module per subsystem where practical. Shared verbatim by both platforms.
• src/platform/win32/, src/platform/linux/ — entry points, input, audio, video, settings, crash reporting; src/platform/platform.h is the seam.
• src/video/ — FMV playback: a shared state machine over plat_video_* (MCI on Windows, ffmpeg on Linux).
• docs/ — architecture notes: task scheduler, memory layout, classes and vtable conventions, implementation plan, and LINUX_PORT.md for the port.
• src/third_party/ — vendored single-file decoders (stb_vorbis.c, simplewebp.h); their licences are in THIRD_PARTY_NOTICES.txt.
• tests/ — build/verification scripts (compile gate, frame comparison).
• tools/ — tools used to help decompilation

Every rewritten function carries its original address as a comment, and every named global documents its original variable address, so any line in src/ can be traced back to the Ghidra project.

License

This project is licensed under the GNU General Public License v3.0 — see LICENSE for the full text.

In practice: fork it, port it, mod it — but derivative works have to ship their source under the same terms, so improvements stay available to everyone.

The license covers only the source in this repository (src/, tools/, tests/, docs/). It does not and cannot grant any rights over the original game.

Legal notice

• No game assets are distributed here. The repository contains source code only; assets\ is git-ignored. Running the build requires your own legally obtained copy of Resident Evil for PC (the GOG or 1997 retail USA release, or the Japanese Biohazard PC release) to supply the data files.
• Resident Evil, its code, assets, characters and trademarks are the property of CAPCOM CO., LTD. This project is an independent reverse-engineering and preservation effort, not affiliated with, authorized, endorsed or sponsored by Capcom in any way.
• The decompiled logic in src\ is derived from the original executable for interoperability, documentation and preservation purposes. It is published in the belief that this constitutes fair use / lawful reverse engineering in the contributors' jurisdictions; no rights over Capcom's copyrighted work are claimed or granted.