C++ game engine built to explore high-performance architecture.
Currently under active development, serves as both a learning platform and research project.
Or it might just be a playground to test my sanity.
Important
My original Bachelor's Thesis version is archived in the thesis branch.
Honestly? I just really love this stuff.
It started with my Bachelor's Thesis: a dual-renderer engine benchmarking Vulkan path tracing against traditional OpenGL PBR. The focus was purely real-time graphics, so the architecture underneath was single-threaded. It worked, and I had a blast building it!
Then I watched Christian Gyrling's GDC talk, Parallelizing the Naughty Dog Engine Using Fibers, and saw how they saturate every core on the CPU. It made me realise how much I still had left to explore.
So I restarted Luth from scratch to chase exactly that: fiber-based job systems, lock-free memory, bindless Vulkan, and hardware ray tracing. It is absolutely over-engineered for a solo project, but that’s the point.
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| Bistro · clustered Forward+, ray-traced sun shadows | Emissive meshes · ReSTIR area lights, path-traced |
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| Subsurface skin · authored in the node material graph | Volumetric god rays · froxel fog |
Skeletal animation and GPU skinning
More shots land with each release.
Prerequisites:
- OS: Windows 10 / 11
- Compiler: MSVC (v143+) or Clang (C++20-compliant)
- GPU: Hardware ray tracing required (
VK_KHR_ray_query+ acceleration structures). NVIDIA RTX 20-series or newer, AMD RX 6000+, or Intel Arc - SDK: Vulkan SDK 1.3+, with
dynamicRendering,timelineSemaphore, descriptor indexing (UBO update-after-bind), and the KHR ray-tracing extensions
Steps:
- Clone with submodules
git clone --recursive https://github.com/Hekbas/Luth.git
- Generate the VS solution
scripts/setup/setup_windows.bat
- Build. Either open
Luth.slnin Visual Studio 2022, or run the headless script:scripts/build/build_windows.bat
The editor binary lands at bin/windows-x86_64/Debug/Runtime/Luthien.exe.
The short tour. Full detail lives in ARCHITECTURE.md and the per-system references under docs/development/arch/.
- Fiber job system. One worker thread per core. Logical tasks run as lightweight, migratable fibers that yield to the scheduler instead of blocking the OS, so the CPU stays near-saturated. FLS, Chase-Lev work-stealing deques, lock-free queues, spin-locks on the hot path. The context switch is hand-written x86-64 assembly over
VirtualAllocstacks, so every fiber stack is AddressSanitizer-trackable. - Pipelined frames. Game (N), Render (N-1), and GPU (N-2) run at the same time. The handoff between stages is an immutable per-frame snapshot, never shared mutable state.
- Tagged allocators. No
new/deleteon the hot path. A Naughty Dog-style Onion/Garlic split: CPU and GPU tagged page allocators (bulk-freed by tag, GPU pages retiring on the timeline) plus a per-frame linear allocator. - Bindless Vulkan 1.3. Dynamic rendering and timeline semaphores only, no legacy render passes or fences. One global texture array and buffer device addresses mean draws carry integer indices instead of rebinding.
- Render graph. Each frame builds a DAG of passes that declare their reads and writes. The graph solves barriers, culls unused passes, and records commands in parallel across workers.
The scheduler, allocators, and lock-free primitives run under a dedicated 28-case ASan stress harness.
| Real-Time Ray Tracing | Hardware ray query: RT sun shadows, ReSTIR direct + global illumination, stochastic RT reflections. Per-frame TLAS, bindless geometry table |
| Path-Traced Reference | rayQuery megakernel with multi-bounce next-event estimation and progressive accumulation. Ground truth to A/B the real-time path |
| Denoising | SVGF across three channels (diffuse DI, indirect GI, specular) behind a swappable IDenoiser |
| Clustered Forward+ | Log-slice light clusters with a slim G-buffer prepass, ECS-driven |
| Lights | Directional sun, plus clustered and GPU-culled point and spot lights |
| PBR Materials | Cook-Torrance metallic/roughness with Opaque, Cutout, and order-independent Transparent modes |
| Node Material Editor | Blender-style graph that generates Slang per material, identical raster and RT output, live recompile, exposed parameters |
| Shading Models | Clear coat, anisotropy, dielectric transmission (glass), sheen (cloth), and subsurface scattering (skin), across the raster and path-traced paths |
| Surface Detail | Parallax occlusion mapping and projected decals, authored in the node graph |
| Shadows | RT ray-query sun shadows by default; 4-cascade PSSM kept as an A/B toggle |
| Volumetric Fog | Froxel grid: inject, integrate, temporal resolve, composite. Optional per-froxel RT fog shadows |
| Ambient Occlusion | GTAO half-res compute (prefilter, horizon integral, bilateral denoise) |
| IBL | HDR skybox, diffuse irradiance, pre-filtered specular, BRDF LUT, split-sum ambient |
| Anti-Aliasing | TAA plus specular anti-aliasing |
| Vertex Deformation | GPU compute deformation shared by raster and the RT BLAS, driven by procedural wind |
| GPU Culling | Compute frustum culling per cascade and main scene, indirect draws throughout |
| Async Compute | Three-queue Vulkan topology (graphics, async compute, transfer); GTAO and RT chains overlap on the compute queue |
| Bindless | Buffer device addresses and one global 16k-texture array; integer material and texture indices |
| Post-Processing | HDR pipeline: bloom, ACES and AgX tonemap operators, vignette, grain, chromatic aberration |
| Shaders | Slang-only asset pipeline with UUIDs, hot-reload, and SPIRV-Cross reflection |
| Pipeline Cache | Disk-persisted, lazy variant creation, targeted hot-reload invalidation |
| Sampling | Fiber-parallel keyframe evaluation |
| GPU Skinning | Bone-matrix SSBO, vertex-shader skinning |
| Blending | SQT interpolation, crossfade transitions, layered override with bone masks |
| Root Motion | Extracted and applied to the entity transform |
| Debug | Bone overlay in the editor viewport |
| Backend | Jolt Physics, jobified onto the fiber scheduler |
| Rigid Bodies | Static / Kinematic / Dynamic with CCD; primitive, convex-hull, and mesh shapes |
| Materials | UUID-keyed friction / restitution / density with hot-reload |
| Character Controller | Kinematic capsule (JPH::CharacterVirtual) with stair-stepping and stick-to-floor |
| Queries | Raycast and overlap (box / sphere / capsule), layer-mask filtered |
| Events | Contact and trigger add/remove, drained per frame |
| Debug Draw | Wire colliders colored by motion state or ground state |
| Asset Database | UUID registry with .meta sidecars; importers for shaders, textures, models, materials, animations |
| Smart Import | Multi-strategy texture discovery, drag-and-drop with eager import, texture remap dialog |
| Texture Compression | Import-time BCn: BC7 for color, BC5 for normals, uploaded on the transfer queue |
| Model Import | Full DCC hierarchy, cameras, and lights, not just meshes; render-mode and cull flags from the source |
| Hot Reload | FileWatcher-driven live reload for shaders, textures, and project files |
| Scene Format | JSON .luth with dirty tracking and native file dialogs |
| Scene Interaction | Mouse picking, selection outlines, multi-select, shade modes (Lit / Wireframe / Unlit and debug views) |
| Inspector | Material editor, animation controls, light and shadow settings, per-component copy/paste, Add Component |
| Live Preview | Orbit-camera 3D preview for material and model assets |
| Play Mode | Editing / Playing / Paused state machine, JSON scene snapshot, transport bar |
| Game Panel | Camera-driven runtime view with letterbox, no overlays |
| Project Panel | Folder navigation, search, rendered thumbnails, context menus |
| Undo / Redo | Command pattern with UUID entity resolution, gizmo-drag coalescing, compound commands |
| Frame Debugger | Freeze a frame, scrub through every draw, replay any single one to see what it did |
| Profiler | Scheduler, memory, and per-pass GPU dashboard with fiber-aware instrumentation |
| GPU Crash Debugging | Nsight Aftermath device-lost dumps plus tiered Vulkan validation |
| Console | Per-subsystem log channels with level filter and search |
| Persistence | Named workspaces: window layouts and panel state saved across sessions |
See the development roadmap for completed work and version history, and FUTURE.md for the long-tail wishlist.
Next up: GPU particle system, scripting (C# or Lua), prefab system, animation blend trees and IK, procedural sky.
Luth is built on the shoulders of giants:
| Vulkan SDK | Rendering backend |
| Slang | Shader language and compiler (SPIR-V) |
| SPIRV-Cross | Shader reflection |
| VMA | Vulkan memory allocator |
| EnTT | Entity-Component-System |
| ImGui | Editor GUI |
| ImGuizmo | Gizmos and the node graph editor widget |
| Phosphor Icons | Editor icon set |
| Tracy | Frame profiler |
| Nsight Aftermath | GPU crash dumps on device-lost (optional) |
| GLFW | Windowing and input |
| GLM | Math |
| spdlog | Logging |
| assimp | Model importing |
| stb_image | Image loading |
| bc7enc_rdo | BCn texture compression (BC7 / BC5 / BC1) |
| nlohmann/json | JSON serialization |
| Jolt Physics | Rigid-body physics |
Luth implements ideas from these papers and talks. If you want to understand a system, start here.
| Area | Source |
|---|---|
| Fiber job system | Gyrling, Parallelizing the Naughty Dog Engine Using Fibers (GDC 2015) |
| Clustered Forward+ | Olsson, Billeter, Assarsson, Clustered Deferred and Forward Shading (HPG 2012) |
| ReSTIR direct lighting | Bitterli et al., Spatiotemporal Reservoir Resampling (SIGGRAPH 2020) |
| ReSTIR global illumination | Ouyang et al., ReSTIR GI: Path Resampling for Real-Time Path Tracing (HPG 2021) |
| SVGF denoising | Schied et al., Spatiotemporal Variance-Guided Filtering (HPG 2017) |
| Ground-truth AO | Jimenez et al., Practical Real-Time Strategies for Accurate Indirect Occlusion (SIGGRAPH 2016) |
| Volumetric fog | Wronski, Volumetric Fog (SIGGRAPH 2014); Hillaire, Physically Based Volumetric Rendering (2015) |
| Temporal AA | Karis, High-Quality Temporal Supersampling (SIGGRAPH 2014) |
| Specular AA | Tokuyoshi, Kaplanyan, Improved Geometric Specular Antialiasing (i3D 2019) |
| PBR shading | Burley, Physically Based Shading at Disney (2012); Karis, Real Shading in Unreal Engine 4 (2013) |
| Tonemapping | Troy Sobotka, AgX |
Released under the MIT License.