An open-source, clean-room reimplementation of Dungeon Siege (Gas Powered Games, 2002) in C# / .NET 11 — 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.
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.
First playable alpha available: v0.0.1 — a self-contained Windows x64 build. Unzip, run SiegeFX.Runtime.exe (standard GOG/Steam/Microsoft installs are auto-detected; otherwise set SIEGEFX_DS1 to your Dungeon Siege folder), and see how far you can take the campaign. 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 — 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: the end-to-end campaign, time-of-day (mood [sun] tables + hour-gated cricket emitters are parsed but parked), interior lighting fidelity, level-up feedback, 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.
src/
SiegeFX.Core class library — file format parsers, no UI
SiegeFX.Tools unified `siegefx` CLI (tank info/list/extract, raw info/decode)
SiegeFX.Browser WPF asset explorer
SiegeFX.Runtime game / engine host (Silk.NET)
SiegeSmith modding studio & world builder built on the same parsers
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.
dotnet build
Then from src/SiegeFX.Runtime:
dotnet run -c Release
See Building and Running for game-data setup and controls.
- Guilherme Lampert — reverse-engineering-dungeon-siege — canonical documentation of Tank, ASP, SNO, RAW formats (MIT). Most of
SiegeFX.Coreis 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
.prsanimation.
MIT. See LICENSE.