GitHub - themuffinator/OpenPrey: A complete Prey (2006) engine/game binary replacement for modern PCs - stock-asset compatible and QoL focused.

A modern, open-source engine and game-code replacement for Prey (2006)

Warning

Development Notice: This project leans heavily on exploratory, agentic AI "vibe coding" for speed. If you want a traditionally engineered codebase, this isn't for you.

About

The OpenPrey Project is a minimal, Prey-focused adaptation of the current OpenQ4 codebase. The project keeps the modernization work that makes current builds practical to develop and debug, but retargets the engine, tooling, and game-library workflow around Prey (2006) and its unified game-module model.

What You Need

To use OpenPrey, you need:

A legitimate copy of Prey (2006)
OpenPrey engine binaries from this repository
A supported host system for the current build/package flow: Windows x64, Linux x64, or macOS arm64

Note

OpenPrey does not include commercial Prey assets. On Windows, fs_basepath auto-discovery checks a valid override first, then the current working directory, registry install entries (including App Paths and uninstall metadata), and finally known legacy install roots such as Human Head Studios/Prey, 2K Games/Prey, and Games/Prey.

Features

Core Features

Prey-first Runtime Layout: Unified openprey/ staging for engine overlays, game modules, GUI scripts, shaders, maps, and strings
Unified Game Module Model: Engine prefers game_<arch> for both SP and MP, with legacy gamex86/gamex64 aliases still accepted during migration
Legacy Install Discovery: Windows install detection supports CD-era registry keys, App Paths, uninstall entries, and known install roots instead of assuming Steam/GOG-only layouts
Official Asset Validation: Startup validation checks the required official Prey base PK4 layout before the game continues

Modernization And Tooling

SDL3-first Windows Backend: SDL3 is the default window/input/display backend; the legacy Win32 backend remains transitional
Meson + Ninja Build System: Canonical configure/build/install path with repo-local staging under .install/
Cross-platform Nightly Builds: GitHub Actions builds and packages Windows, Linux, and macOS artifacts from the same Meson staging flow
Debug-Oriented Local Workflow: .install/ for staged runtime files, .home/ for configs/logs/saves, .tmp/ for task artifacts
Crash Diagnostics: Windows debug builds write crash logs and minidumps into crashes/ beside the executable

Runtime And Display Improvements

Modern Window Modes: Windowed, borderless, desktop-native fullscreen, and exclusive fullscreen behavior are all supported
Monitor Selection: SDL3 builds expose r_screen, listDisplays, and listDisplayModes for multi-monitor setup
Staged Validation Launches: Repo-local launch workflows keep logs in .home/logs/openprey.log and avoid writing back into the staged runtime tree

Compatibility Status

This status focuses on compatibility with official Prey assets and the OpenPrey game-library pipeline, not binary interchangeability with proprietary retail DLLs.

Landed

Project Rebrand Completed: Meson project metadata, staged binaries, VS Code launch settings, and documentation now use OpenPrey naming
Prey Install Discovery Path: fs_basepath auto-detection now targets Prey registry/app-path/uninstall metadata and legacy install roots
Unified Game Module Loader: OpenPrey builds and stages a unified game_<arch> module under openprey/
Companion Repo Tooling: Sync/build tooling now targets OpenPrey-GameLibs and supports both Meson-wrapper and legacy VC-solution layouts
Official PK4 Layout Validation: Engine startup rejects missing or modified required base-pack layouts when fs_validateOfficialPaks 1 is enabled
Cross-host Meson Support: Meson source selection, dependency wiring, and nightly packaging now cover Windows, Linux, and macOS hosts

In Progress

Stock-asset SP/MP Smoke Validation: Default staged launch flow is still being verified across single-player and multiplayer startup cases
Prey Gameplay Bring-up: Active src/Prey game-library integration and runtime verification continue during the migration
Particle And FX Compatibility: Doom 3 / Prey-era particle behavior and dependent runtime paths still need restoration and parity checks
Cross-host Runtime Validation: Windows remains the deepest runtime-validation path while Linux/macOS map validation is extended

Not Yet Claimed

Full Campaign Completion: The project does not yet claim end-to-end single-player completion against stock assets
Multiplayer Parity: Multiplayer compatibility remains under active validation

Current follow-up work is tracked in TODO.md, docs-dev/release-completion.md, and docs-dev/prey-gamelibs-compatibility-plan.md.

Quick Start

Prerequisites

Prey (2006) installed from original media or another legitimate distribution
Supported build hosts: Windows x64, Linux x64, or macOS arm64
Build tools: Meson, Ninja, and Python 3
Windows compiler/toolchain: Visual Studio 2026+ recommended (MSVC 19.46+)
Linux compiler/toolchain: GCC or Clang plus system glew, openal, x11, xext, and xxf86vm development packages
macOS compiler/toolchain: Apple Clang with Homebrew glew

Note

tools/build/meson_setup.ps1 automatically syncs ../OpenPrey-GameLibs on setup, compile, and install. Clone the companion repo alongside OpenPrey, or set OPENPREY_SKIP_GAMELIBS_SYNC=1 if you intentionally want to build only from the in-repo mirror.

Installation

Clone the repositories

git clone https://github.com/themuffinator/OpenPrey.git
git clone https://github.com/themuffinator/OpenPrey-GameLibs.git
cd OpenPrey

Build and stage OpenPrey

Windows (PowerShell)

# Setup the build
powershell -ExecutionPolicy Bypass -File tools/build/meson_setup.ps1 setup --wipe builddir . --backend ninja --buildtype=debug --wrap-mode=forcefallback

# Compile
powershell -ExecutionPolicy Bypass -File tools/build/meson_setup.ps1 compile -C builddir

# Stage the local runtime package
powershell -ExecutionPolicy Bypass -File tools/build/meson_setup.ps1 install -C builddir --no-rebuild --skip-subprojects

Linux / macOS (bash)

# Setup the build
bash tools/build/meson_setup.sh setup --wipe builddir . --backend ninja --buildtype=release -Dplatform_backend=sdl3

# Compile
bash tools/build/meson_setup.sh compile -C builddir

# Stage the local runtime package
bash tools/build/meson_setup.sh install -C builddir --no-rebuild --skip-subprojects

Run the staged build

Set-Location .install
.\OpenPrey-client_x64.exe +set fs_game openprey +set fs_savepath ..\.home +set logFile 2 +set logFileName logs/openprey.log +set r_fullscreen 0

For a short single-player smoke test, append +set si_gameType singleplayer +map game/roadhouse_quick.

Building from Source

Detailed Build Instructions

Requirements

Meson 1.2.0 or newer
Ninja build system
Python 3
Windows toolchain: Visual Studio 2026 / MSVC 19.46+ recommended
Linux toolchain: GCC or Clang with system OpenGL/X11/OpenAL development packages
macOS toolchain: Apple Clang with Homebrew glew

Build Options

-Dbuild_engine=true|false         # Build OpenPrey-client_<arch> and OpenPrey-ded_<arch>
-Dbuild_games=true|false          # Build the unified game module from the synchronized mirror
-Dplatform_backend=sdl3|legacy_win32|native
-Duse_pch=true|false
-Denforce_msvc_2026=true          # Fail configure if MSVC is older than 19.46+

Build Commands

Windows (PowerShell)

# Configure
powershell -ExecutionPolicy Bypass -File tools/build/meson_setup.ps1 setup builddir . --backend ninja --buildtype=release

# Build
powershell -ExecutionPolicy Bypass -File tools/build/meson_setup.ps1 compile -C builddir

# Stage the runtime tree used for local validation
powershell -ExecutionPolicy Bypass -File tools/build/meson_setup.ps1 install -C builddir --no-rebuild --skip-subprojects

From a Developer Command Prompt

tools\build\openprey_devcmd.cmd
meson setup builddir . --backend ninja --buildtype=release
meson compile -C builddir
meson install -C builddir --no-rebuild --skip-subprojects

Linux / macOS

# Configure
bash tools/build/meson_setup.sh setup builddir . --backend ninja --buildtype=release -Dplatform_backend=sdl3

# Build
bash tools/build/meson_setup.sh compile -C builddir

# Stage the runtime tree used for local validation
bash tools/build/meson_setup.sh install -C builddir --no-rebuild --skip-subprojects

Output Files

Build directory (builddir/):

OpenPrey-client_x64.exe - main engine executable
OpenPrey-ded_x64.exe - dedicated server executable
openprey/game_x64.dll - unified game module
import libraries and PDBs may be present in local debug builds

Staging directory (.install/):

OpenPrey-client_x64.exe
OpenPrey-ded_x64.exe
OpenAL32.dll when a bundled Windows runtime is available
.install/openprey/game_x64.dll
.install/openprey/{glprogs,guis,maps,materials,script,strings}/

meson install creates the local runtime tree used for testing and packaging input. Release packaging strips build-only artifacts such as .pdb, .lib, .exp, and .ilk.

Nightly Packaging

GitHub nightly builds package the staged .install/ tree into:

openprey-<version-tag>-windows.zip
openprey-<version-tag>-linux.tar.xz
openprey-<version-tag>-macos.tar.gz
openprey/game_<arch>.(dll|so|dylib) stays as a loose runtime module inside the packaged openprey/ directory
staged overlay content is bundled into openprey/pak0.pk4
Linux nightlies include staged share/applications and share/icons payloads
macOS nightlies include an OpenPrey.app launcher bundle beside the packaged binaries
the workflow publishes or updates a nightly-<version-tag> GitHub release with generated notes

Game Directory Structure

OpenPrey uses a unified runtime directory layout under openprey/:

.install/
|-- OpenAL32.dll                  # optional bundled runtime on Windows
|-- OpenPrey-client_x64.exe
|-- OpenPrey-ded_x64.exe
\-- openprey/
    |-- game_x64.dll
    |-- glprogs/
    |-- guis/
    |-- maps/
    |-- materials/
    |-- script/
    \-- strings/

The engine uses the unified module model for both game modes:

Single-player: loads game_<arch> from openprey/
Multiplayer: loads the same unified game_<arch> module
Legacy compatibility: gamex86 / gamex64 aliases are still accepted during migration

SDK And Game Library

OpenPrey keeps SDK-derived game code in the companion OpenPrey-GameLibs repository. Canonical edits for SDK/game-library work belong there first; src/game in this repo is a synchronized mirror used by the Meson build, with additional src/Prey and src/preyengine sync paths brought in as needed for compatibility work.

Companion Workflow

Default companion repo location: ../OpenPrey-GameLibs
tools/build/meson_setup.ps1 syncs the companion repo before setup, compile, and install
OPENPREY_BUILD_GAMELIBS=1 triggers an additional companion build-and-stage pass during compile
tools/build/build_gamelibs.ps1 can consume either a Meson wrapper or the current legacy src/PREY.sln layout
Legacy OPENQ4_* environment variable names are still accepted as temporary migration aliases

Prey SDK License

The companion repo contains code derived from the Prey Software Development Kit and is subject to the original Human Head Studios SDK license.

The bundled SDK EULA allows non-commercial Prey modifications that run only with a legitimate copy of Prey, but it prohibits commercial exploitation and standalone redistribution of the SDK-derived code. See EULA.Development Kit.rtf in the OpenPrey-GameLibs repository for the full terms.

Project Goals

Primary Objectives

Deliver a minimal, clean OpenQ4-to-Prey adaptation
Preserve behavior expected by shipped Prey assets where practical
Keep single-player and multiplayer behavior aligned with Prey's unified game-library model
Prefer Doom 3 / Prey lineage behavior over inherited Quake 4 behavior where Prey depends on it
Keep runtime staging and packaging centered on a single openprey/ directory

Non-Goals

Shipping proprietary Prey assets
Reintroducing the old OpenQ4 closed-source companion-repo workflow
Assuming Steam/GOG-only install layouts for Prey (2006)
Fixing compatibility by shipping content hacks instead of repairing engine/game code

Documentation

Platform Support - Windows-first platform roadmap and SDL3 direction
Porting Baseline - current OpenQ4 -> OpenPrey migration assumptions
GameLibs Compatibility Plan - companion repo integration and game-library bring-up status
Display Settings - fullscreen, borderless, monitor selection, and windowed sizing
Input Key Matrix - keyboard and input reference
Official PK4 Checksums - required Prey base pack layouts and published checksums
Release Completion - shipped work and carry-forward items
Project TODO - known issues and near-term tasks

Asset Validation

OpenPrey validates the official Prey base-pack layout at startup when fs_validateOfficialPaks 1 is enabled (default).

How it works:

Engine scans the detected base/ pack set
Chooses the required layout to validate against:
- classic retail naming (pak000.pk4 ... pak004.pk4)
- consolidated retail naming (pak_data.pk4, pak_sound.pk4, pak_en_v.pk4, pak_en_t.pk4)
Refuses to continue if the required packs are missing or modified

Current checksum status:

Consolidated retail pack checksums are published in official-pk4-checksums.md
Classic retail pack names are enforced by presence, while canonical checksum capture is still being finalized

Advanced Configuration

Display And Graphics Settings

Monitor Selection

r_screen -1 - auto-select current display (default)
r_screen 0..N - force a specific monitor on SDL3 builds
listDisplays - list monitor indices
listDisplayModes [displayIndex] - list exclusive fullscreen modes for a display

Display Modes

r_fullscreen 0|1 - windowed vs fullscreen
r_fullscreenDesktop 1 - desktop-native fullscreen (default)
r_fullscreenDesktop 0 - exclusive fullscreen using r_mode/r_custom*
r_mode -2 - request native desktop resolution for fullscreen mode selection
r_borderless 1 - borderless window when r_fullscreen 0

Windowed Sizing

r_windowWidth / r_windowHeight - window size when running windowed
Validation workflows should force +set r_fullscreen 0

File System And Validation Settings

Path Variables

fs_basepath - detected Prey install root
fs_homepath - writable user path
fs_savepath - save/config/log path (defaults to fs_homepath)
fs_game - active game directory (openprey)
fs_devpath - optional developer override path used by local debug workflows

Validation

fs_validateOfficialPaks 1 - verify required official base packs at startup
Launching from .install/ keeps the staged runtime overlay on the search path while letting .home/ hold writable state

Dependencies

OpenPrey resolves engine dependencies through Meson subprojects and bundled Windows runtime assets:

Library	Version	Purpose
SDL3	3.4.0	Windowing, input, display management
GLEW	2.3.4	OpenGL extension loading
OpenAL Soft	bundled Windows package	3D audio runtime
stb_vorbis	1.22	Ogg Vorbis decoding

Debugging And Development

Local Validation Loop

Launch from .install/ in windowed mode with +set r_fullscreen 0
Use +set fs_savepath ..\.home and +set logFileName logs/openprey.log to keep logs local to the repo
Inspect .home\logs\openprey.log after each short run
Fix warnings/errors in engine/game/parser/loader code before resorting to content-side workarounds

Build Automation

tools/build/meson_setup.ps1 auto-detects and initializes the Visual Studio developer environment when needed
compile -C builddir auto-runs setup --wipe if the build directory is missing or invalid
install auto-adds --skip-subprojects when omitted
tools/build/openprey_devcmd.cmd is available if you want a reusable MSVC developer shell

Companion Repo Integration

Use OPENPREY_GAMELIBS_REPO=<path> to override the companion repo location
Use OPENPREY_SKIP_GAMELIBS_SYNC=1 to suppress automatic mirror sync
Use OPENPREY_BUILD_GAMELIBS=1 to build companion game libraries during compile
Use OPENPREY_SKIP_GAMELIBS_BUILD=1 to skip that additional companion build step

Contributing

OpenPrey is open to contributions, but the project has a few hard constraints:

Keep compatibility work centered on stock Prey assets
Edit SDK-derived sources in OpenPrey-GameLibs first; treat src/game here as a synchronized mirror
Preserve the unified openprey/ runtime layout
Keep documentation updated when workflow, naming, or repository structure changes
Prefer engine/game fixes over shipping replacement assets or content hacks

License

OpenPrey is licensed under the GNU General Public License v3.0 (GPLv3).

The GPLv3 license applies to OpenPrey's engine code in this repository.

SDK-derived game-library code in OpenPrey-GameLibs remains subject to the original Prey SDK license.

Prey game assets are proprietary and are not distributed with OpenPrey.

Credits

OpenPrey builds on work from multiple projects and teams:

Core Contributors

themuffinator - OpenPrey development and maintenance
Justin Marshall - Quake4Doom baseline and related reverse-engineering work
Robert Backebans - RBDOOM-3-BFG modernization work that informs this ecosystem

Original Developers

id Software - id Tech 4 lineage
Raven Software - Quake 4 codebase lineage used by OpenQ4
Human Head Studios - Prey (2006) and the Prey SDK

Third-Party Libraries

Sean Barrett - stb_vorbis
GLEW contributors
OpenAL Soft contributors
SDL contributors

Links

Disclaimer

OpenPrey is an independent project and is not affiliated with, endorsed by, or sponsored by Human Head Studios, 2K, Bethesda, ZeniMax, id Software, or Raven Software.

You must own a legitimate copy of Prey (2006) to use this software. OpenPrey does not include any copyrighted game assets.

Use At Your Own Risk

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND. OpenPrey is experimental software under active development. Use it at your own risk.

Name		Name	Last commit message	Last commit date
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.github		.github
.install		.install
.vscode		.vscode
assets		assets
docs-dev		docs-dev
docs-user		docs-user
openprey		openprey
references		references
src		src
subprojects		subprojects
tools		tools
.gitattributes		.gitattributes
.gitignore		.gitignore
AGENTS.md		AGENTS.md
LICENSE		LICENSE
README.md		README.md
TODO.md		TODO.md
meson.build		meson.build
meson_options.txt		meson_options.txt

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About

What You Need

Features

Core Features

Modernization And Tooling

Runtime And Display Improvements

Compatibility Status

Landed

In Progress

Not Yet Claimed

Quick Start

Prerequisites

Installation

Building from Source

Requirements

Build Options

Build Commands

Output Files

Nightly Packaging

Game Directory Structure

SDK And Game Library

Companion Workflow

Prey SDK License

Project Goals

Primary Objectives

Non-Goals

Documentation

Asset Validation

Advanced Configuration

Monitor Selection

Display Modes

Windowed Sizing

Path Variables

Validation

Dependencies

Debugging And Development

Local Validation Loop

Build Automation

Companion Repo Integration

Contributing

License

Credits

Core Contributors

Original Developers

Third-Party Libraries

Links

Disclaimer

Use At Your Own Risk

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