DUDE — Doom3 Unified Development Engine

DUDE is a fork of dhewm3 (itself the GPL source port of DOOM 3) that modernizes the renderer while keeping the classic DOOM 3 look and gameplay faithful. The stock renderer's ARB assembly shaders are translated to a shared GLSL source tree serving two new backends — OpenGL 3.3 core and Vulkan (1.4, with hardware ray tracing where available) — selectable via the r_graphicsAPI cvar, with the original ARB renderer kept intact as the faithful reference. All visual enhancements are opt-in, driven by in-game quality presets whose floor is the unmodified classic look.

License note: DUDE is a modified version of dhewm3, based on id Software's Doom 3 GPL source release. All DUDE-authored source in this repository — including every file under neo/shaders/ and files without an explicit license header — is licensed under the GNU GPLv3 (see COPYING.txt). Third-party components (Dear ImGui, VMA, FSR2, SMAA, stb) keep their original licenses, stated in their files. No game assets are included or redistributable here: the base/*.pk4 game data is proprietary id/Bethesda content — bring your own Doom 3 installation.

Features

Renderers (r_graphicsAPI opengl | opengl3 | vulkan)

• Legacy OpenGL/ARB path (opengl, the default) — untouched, the faithful reference.
• OpenGL 3.3 core — the stock look re-expressed in GLSL, plus the enhancement suite.
• Vulkan 1.4 — same enhancement suite, plus Vulkan-only features below. VMA-managed memory, persistent scene buffers, GPU timestamps (r_vkGpuTime).

Opt-in enhancement suite (GL3 + Vulkan; presets Potato → Nightmare in the classic System menu, "Potato" = unmodified classic rendering)

• Shadow maps: cube shadows with rotated-Vogel PCF, sun/parallel-light shadow maps (stencil shadows remain the fallback and the faithful default).
• HDR pipeline, SSAO, PBR (GGX) with screen-space reflections, parallax occlusion mapping, soft particles, baked per-material AO maps.
• Anti-aliasing: SMAA 1x / FXAA, and AMD FSR2 in Native-AA mode (motion vectors + jittered projection) on Vulkan.
• Smaller touches: depth-of-field on weapon reload, self-lit pickup glow, emissive GUI surfaces casting light, smoke-in-darkness blending, hi-res GUI font atlases.

Gameplay

• Ultra Nightmare difficulty (unlocked with Nightmare): Nightmare rules plus permadeath — one checkpoint per run written at map starts only, no manual saves, erased when you die (docs/ultra-nightmare.md).

Vulkan-only

• Ray-traced sun shadows (r_rtSunShadows) via VK_KHR_ray_query on RT-capable GPUs.
• GPU tessellation for characters/monsters (PN triangles + displacement), GPU skinning.
• Parallel image decode on level load, buffer-device-address batched indirect depth prepass, and other GPU-driven experiments (see docs/gpu-offload-plan.md).

Engine quality-of-life

• com_interpolate — render above 60 fps while the game simulates at its native 60 Hz.
• com_classicTics — Doom 3's original 62.5 Hz game tic (16 ms, as 1.3.1 ran) instead of 60 Hz, for speedrunners; pair it with com_interpolate (see Configuration.md).
• com_maxFPS frame limiter, SSE4.1 SIMD baseline, runtime ARB→SPIR-V compilation so classic mod shaders work on the new backends, cvar-translation shim for old mods.

Future development — the RTX pipeline

The long-term goal is to progressively replace the raster rendering pipeline with ray tracing on RT-capable hardware. The foundation is already shipped: acceleration-structure infrastructure over the live game scene, VK_KHR_ray_query shading, ray-traced sun shadows, a GPU compute lane, and per-frame GPU-resident deformed geometry for animated models. From there the roadmap (docs/rtx-shadow-roadmap.md) climbs tier by tier:

1. Ray-traced shadows for all lights — replacing shadow maps and stencil volumes with per-pixel traced visibility (the sun tier already works).
2. Ray-traced reflections — replacing screen-space reflections and their off-screen blind spots.
3. Ray-traced ambient occlusion and indirect lighting, converging on a fully ray-traced (path-traced) lighting pipeline in the spirit of the classic-game RTX remasters.

As with everything else in DUDE, the RTX path is additive: the faithful raster renderers remain, both as the default look and as the path for GPUs without ray tracing support.

Supporting the project

If you enjoy DUDE, you can support development at buymeacoffee.com/Inkub0 ☕ — donations go toward new hardware needed to build and test real HDR output support and the RTX pipeline above.

Building

Linux (native):

./build.sh              # GL3 + legacy renderers  -> build/dude
./build.sh --vulkan     # + the Vulkan backend (needs Vulkan headers + glslang)
./run.sh                # launch

Windows (cross-compiled from Linux with mingw-w64):

./build-win.sh          # GL3 + Vulkan            -> dist-win/dude.exe (+ DLLs, self-contained)
./build-win.sh --no-vulkan

Dependencies: CMake, GCC or Clang (C++17 for the Vulkan backend), SDL2 (SDL3 works as a fallback), OpenAL; Vulkan headers + glslangValidator for the Vulkan backend; optional shaderc for runtime mod-shader compilation on Vulkan.

Running

DUDE needs the original DOOM 3 / Resurrection of Evil game data (base/*.pk4, d3xp/*.pk4) from your own copy of the game (the Steam/GOG classic version, not the BFG edition). Point the engine at it with +set fs_basepath /path/to/doom3, or place the pk4s next to the executable. Writable data (configs, saves, screenshots) lives in its own "dude folder" (~/.local/share/dude on Linux, Documents/My Games/dude on Windows).

Quake 4 (in development). The same executable is learning to run the retail Quake 4 from your own install (docs/quake4-port.md). ./run-q4.sh finds a Steam install (or takes Q4DIR=/path/to/Quake 4) and boots its data; until the Quake 4 game library exists it runs a spectator-only "null game" with no gameplay.

Upstream: dhewm3

DUDE is built on dhewm3; everything documented there (game data setup, original compile instructions, mod support, FAQ) applies to DUDE's faithful baseline too:

• Project + README: https://github.com/dhewm/dhewm3
• Homepage: https://dhewm3.org — mods: https://dhewm3.org/mods.html
• FAQ: https://github.com/dhewm/dhewm3/wiki/FAQ

DUDE-specific documentation lives in this repo under docs/ — port architecture, Vulkan backend, and per-feature plans.