Real-Time Indirect Lighting with Radiant GI
Achieving realistic bounce lighting without the long bake times of Enlighten or Progressive Lightmapper is a massive workflow win. Radiant Global Illumination Unity 7.1.1 utilizes a sophisticated screen-space raymarching technique to compute indirect light. By integrating with the URP Render Graph, it provides a performant path for dynamic GI that reacts instantly to moving lights and emissive materials.
Integration Tips
- Deferred Rendering Path: While Forward is supported, I strongly recommend switching your URP or Built-in pipeline to Deferred. This allows Radiant GI to access G-buffer data more efficiently, resulting in more accurate light bounces.
- GI Injectors: For off-screen light sources, place ‘GI Injectors’ (virtual emitters). Screen-space effects usually lose data at the edges of the frustum; these injectors help maintain lighting consistency when the light source isn’t visible.
- Bilateral Filtering: If you notice noise in the indirect shadows, increase the spatio-temporal filter weight. This smooths out the raymarching results across frames without the ghosting typical of cheaper SSGI implementations.
Best Use Cases
1. Dynamic Day/Night Cycles
Baking lighting for every time of day is impossible for large open worlds. Radiant GI provides the necessary light bounces from the skybox and sun to ground your objects in the scene as the light angle changes in real-time.
2. High-Action Shooters with Emissive FX
Muzzle flashes and explosions can act as GI sources. Since every pixel can contribute to the GI, your VFX will naturally illuminate the surrounding environment, drastically increasing the visual impact of combat.