SiegeFX

An open-source, clean-room reimplementation of Dungeon Siege (Gas Powered Games, 2002) in C# / .NET 10, for Windows and Linux — loading the original game's data files directly rather than redistributing any of them.

SiegeFX requires the original game data. It ships no copyrighted assets. You must own a copy of Dungeon Siege (GOG, Steam, or original discs) to use it.

About

SiegeFX loads DS1's .dsres tank archives, parses the GAS template language, runs the original Skrit gameplay scripts on a clean VM, and renders ASP meshes with PRS skeletal animation. Spells, leveling, audio, and save/load are wired against the values DS1 ships in formulas.gas rather than reinvented.

It is clean-room: every claim traces back to headless audits over the bytes the original game ships, and the 2023 leak of the DS1 source is off-limits — you don't need it, just patient tooling. Every claim in the status below is backed by a siegefx audit you can run yourself: see Receipts on the wiki.

Most of the groundwork is other people's — see Credits & prior art.

Current state of development

Latest alpha: v0.5.0, self-contained builds for Windows x64 and Linux x64; every earlier build, back to the first playable v0.0.1, is on the Releases page. On Windows, unzip it and run SiegeFX.exe; on Linux, unpack the tarball and run ./SiegeFX, or install the AUR package siegefx-bin on Arch. GOG and Steam installs are found by themselves (on Linux also through Heroic, Lutris, Bottles and Wine prefixes), or set SIEGEFX_DS1 to your Dungeon Siege folder. Please report what breaks via GitHub issues.

Versioning note: earlier tags tracked internal engine milestones and outpaced the project's playable maturity; the scheme was reset at the first playable build and now tracks progress toward 1.0 = a complete Farmhouse → Castle Ehb campaign. The retired milestone notes live on the wiki's Release Archive.

Alpha software. This is a long-running reverse-engineering project, not finished software. The world's interactive mechanics are function-complete by audit, but the point of the alpha is finding out what real playthroughs hit.

Working today:

• World & navigation — every shipped region streams across boundaries; the live nav mesh drives click-to-move / click-to-attack, cross-region descents into cellars, caves, and dungeons, and Sims-style cutaway fades on the layer above you.
• Party & companions — conversation-driven recruitment; followers that fight with their own gear and trail you through six authentic DS1 formations; a per-companion character sheet (paper doll + backpack) and the Field Commands panel for orders and formation.
• Combat & spells — melee, ranged, and spellcasting enemies with template-driven spawners, pack alerts, and patrol routes; the full authored spell universe firing its own DS1 sfx effects.
• Presentation & UX — a DS1-faithful character creator, scripted intro cinematics (a non-interactive-sequence engine + storyteller narration), a rotating compass, a quest journal and HUD tracker, in-world vendors with retail store chrome, clickable doors, breakable props with authored loot, lossless quicksave/quickload, and streaming mood-driven music.
• Options & comfort — a fully wired options menu in authentic DS1 chrome (resolution, fullscreen/windowed with remembered window size, shadows, texture filtering, gamma, object detail) plus a modern Advanced tab (VSync, frame cap, anisotropy, MSAA, point-light budget, UI scale); Shift+drag HUD rearrangement with snapping; everything persists between sessions.
• Weather & atmosphere — a world clock that runs the authored day: the sun takes the hourly colours DS1 ships, and night-only life such as the crickets sounds only after dark; and the full mood system: per-location scripted rain and snow (the opening-farmland storm, the Glacern blizzards) with authored densities that drift like retail, linear mood fog on every region, wind-sheared precipitation, lightning with thunder, and the placed sound-emitter layer (trigger-activated rain loops, wind beds, waterwheels).
• World mechanics — the moving-node elevator system (216 lifts across 32 regions, lever- and stand-activated, riding the party between floors); openable chests and trapped containers; life/mana shrines that heal and revive; scripted progression gates (stuck doors that open on quest events, key-locked mechanisms, message-broken rubble); the boolean/counter logic-gizmo network quests gate on; and a campaign-wide completability audit whose "unhandled component" table now reads empty across all 81 regions.

Under construction: since v0.4.0 the campaign can be played through to the final boss; the work now is making every part of it behave as the original does, measured row by row on the wiki's Parity page. Still open there: the intro and credits movies (Bink), interior lighting fidelity, and combat balance.

The full per-phase development log, roadmap, and what's queued live on the wiki — start at Status, Architecture, Building and Running, or Engine Quirks and Stumbles.

Project layout

src/
  SiegeFX.Core       class library: file formats, gameplay rules, the parity audits; no UI
  SiegeFX.Audio      OpenAL Soft audio engine and streaming music
  SiegeFX.Runtime    the game (Silk.NET: GLFW + OpenGL 3.3)
  SiegeFX.Tools      the `siegefx` command line: format tools and the headless audits
  SiegeFX.Net.Eos    Epic Online Services multiplayer (needs Epic's SDK; not in the solution)
  SiegeSmith         modding studio & world builder on the same parsers (WPF, Windows)
tests/               data-free unit tests (CI runs them on Linux, macOS and Windows)
tools/               receipts.sh (the pre-push gate), the test-menu generator, ds1/ (the original game under Proton)
packaging/           Linux desktop entry, smoke test, AUR package

SiegeSmith

The repository also ships SiegeSmith — the modding studio and world builder built on the same parsers as the engine. One tool covers the whole loop: browse and view every DS1 format (textures, models, animations with live playback, scripts with compile diagnostics), edit GAS with live validation, package and install mods — and a full World Builder that goes from door-stitched terrain through scatter brushes, patrol routes, triggers, dialogue, quests, weather, and custom imported art, to a one-click playable .dsmap. You can mod Dungeon Siege with it, or build an entirely new game.

Start here: the SiegeSmith wiki section — with the full World Builder Guide, the Making a Game from Scratch walkthrough, and the Modder's Guide.

Build

You need the .NET 10 SDK (global.json pins the band) and your own Dungeon Siege install. The whole solution builds on Linux and on Windows:

dotnet build SiegeFX.sln -c Release

(or ./build-release.sh / build-release.bat). Then run the game:

• Linux: src/SiegeFX.Runtime/bin/Release/net10.0/SiegeFX
• Windows: src\SiegeFX.Runtime\bin\Release\net10.0-windows10.0.22621.0\SiegeFX.exe (the Windows build adds the in-game video recorder)

SiegeFX finds a GOG or Steam install by itself: on Windows through the registry, on Linux where Steam (native, Flatpak or Snap), Heroic, Lutris, Bottles or a Wine prefix put it. Otherwise write your Dungeon Siege folder on the first line of ~/.config/siegefx/ds1path.txt (Windows: %APPDATA%\siegefx\ds1path.txt), or set SIEGEFX_DS1. On Linux the game needs OpenGL 3.3 and, for multiplayer, OpenSSL 3; GLFW and OpenAL Soft come with the build.

./publish.sh vX.Y.Z builds the release artifacts on Linux: the Linux tarballs for x64 and ARM64 (self-contained, with a desktop entry), the macOS tarball for Apple Silicon (its code signatures checked by tools/check-macos-signatures.py), the Windows game zip and the SiegeSmith zip. Internet play rides along when the EOS SDK is unpacked beside the repo; a build from source alone plays on the LAN and by direct IP. publish-alpha.bat builds the Windows two on Windows.

See Building and Running for controls and more.

Checks

• CI builds the solution on Linux (x64 and ARM64), macOS (Apple Silicon) and Windows with warnings as errors, runs the unit tests and the game's self-tests, builds the release artifacts and launches both Linux tarballs and the macOS tarball, each on its own machine, on every push.
• tools/receipts.sh is the gate before a push; it needs a game install: the build, the unit tests, the engine's self-tests, the parity ledger against its committed baseline, and every spell's effect trace against goldens/sfx-timelines.
• siegefx parity ledger <install> measures how much of the original content the engine handles (commands, quests, sounds, template fields, effects…) and lists each gap.
• test-all.bat / test-all.sh: the phase-by-phase test menu, one entry per feature. Edit the .bat; tools/test-menu.sh generates the .sh from it.

Credits & prior art

• Guilherme Lampert — reverse-engineering-dungeon-siege — canonical documentation of Tank, ASP, SNO, RAW formats (MIT). Most of SiegeFX.Core is a port of his work.
• Scott Bilas — GPG's lead engine programmer, whose public writings document the Siege engine internals.
• OpenSiege — github.com/OpenSiege/OpenSiege — earlier C++/OpenSceneGraph reimplementation attempt.
• SiegeTheDay.org — DS1 modding community and original source of the MaxScript importers we lean on for .prs animation.

License

SiegeFX is licensed under the GNU General Public License v3.0 (GPL-3.0-only).

Third-party software

SiegeFX's multiplayer is built on the Epic Online Services (EOS) SDK — © Epic Games, Inc., used under the Epic Online Services terms. Epic, Epic Games, Epic Online Services, and their respective logos are trademarks or registered trademarks of Epic Games, Inc. in the United States and elsewhere. SiegeFX is not affiliated with, endorsed by, or sponsored by Epic Games.

The EOS SDK bundles a number of open-source components; their license notices are reproduced verbatim in THIRD-PARTY-NOTICES.txt, which also ships alongside each release build.