LuminaGI: A Real-Time Global Illumination System Inspired by Unreal Lumen
Ruotong GUAN
Software Development
LuminaGI: A Real-Time Global Illumination System Inspired by Unreal Lumen
LuminaGI is a real-time global illumination system built from scratch on a custom DirectX 12 rendering engine. It targets the longstanding problem of producing dynamic multi-bounce diffuse indirect lighting— color bleeding, soft contact shadows, and stable indoor ambience— without relying on hardware ray tracing. Rather than using baked lightmaps or offline path tracing, LuminaGI adapts the architectural ideas behind Unreal Engine 5’ s Lumen and recent academic radiancecaching work into a compact, fully software-traced GPU pipeline.
probe pipeline that gathers final-frame indirect lighting via importance-sampled signed distance field tracing. A two-stage spherical harmonics integration converts thousands of stochastic samples into smooth, temporally stable irradiance with minimal flicker. The implementation includes per-instance mesh SDF baking with BVH acceleration, a global SDF clipmap, dirty-card-driven incremental updates for moving lights, and a Lumenstyle importance sampling scheme that reuses the previous frame’ s lighting history.
The system runs on three cooperating data structures: a six-axis surface cache atlas that captures each mesh’ s outgoing radiance at high spatial resolution, a world-space voxel lighting volume that propagates light between cards across multiple bounces, and a screen-space
LuminaGI achieves an interactive frame rate of approximately 120 FPS at 1080p on a desktop RTX GPU, producing convincing diffuse global illumination with full multi-bounce energy and graceful degradation under continuous camera and light motion.
86 SOFTWARE DEVELOPMENT