Introduction

What is Radiant GI?

Radiant Global Illumination is a real-time, screen-space global illumination asset for Unity's Universal Render Pipeline (URP). It computes indirect diffuse lighting entirely on the GPU with zero pre-computation, making it ideal for dynamic scenes, procedural content, and any surface or light source.

Unlike baked GI solutions, Radiant works instantly with moving objects, changing lights, and runtime-generated geometry. It integrates as a standard URP Renderer Feature and Volume override, so it fits seamlessly into any existing URP project.

Key Features

Global Illumination

• Screen-Space GI — real-time indirect diffuse lighting computed per frame with no baking required.
• Forward & Deferred — works with both URP rendering paths; deferred produces the most realistic results.
• Multi-Bounce — optional extra bounce pass reuses previous-frame data for richer light propagation at minimal cost.
• Near Field Obscurance — integrated ambient occlusion consistent with the indirect lighting, similar to SSAO but at no extra pass cost.
• Specular Indirect — optional specular reflections driven by the GI data.

Fallback Systems

• APV / Sky — leverages Adaptive Probe Volumes or sky ambient for off-screen contribution.
• Reflection Probes — samples nearby reflection probe cubemaps when rays miss in screen space.
• Reflective Shadow Maps — renders the scene from the directional light's point of view for accurate off-screen GI.
• Reuse Rays — ultra-cheap fallback that recycles successful rays from previous frames.

Special Features

• Virtual Emitters — place invisible GI light sources anywhere in the scene to simulate off-screen or hidden emitters.
• Organic Light — injects procedural lighting into g-buffers for more natural environment illumination (deferred only).
• Transparent Support — enables light bouncing on transparent surfaces via a global texture or per-object script.
• Stencil Masking — exclude specific objects (UI, FPS weapons) from GI via stencil buffer.
• Volume-Based Control — restrict GI to specific areas using local post-processing volumes.

Debug & Comparison Tools

• Debug Views — inspect intermediate GI buffers, normals, depth, and ray data.
• Compare Mode — split-screen or side-by-side before/after comparison.
• Scene View Preview — visualize GI results directly in the editor without entering Play Mode.

Requirements

Next Steps

Ready to get started? Follow the recommended path:

1. Quick Start — see your first GI result in under 5 minutes.
2. Setup Guide — learn about the Renderer Feature, rendering paths, and volume configuration.
3. Parameters Reference — full list of every setting organized by category.
4. FAQ — common questions answered.