Introduction

Radiant Global Illumination brings screen-space, real-time global illumination to the Built-in Rendering Pipeline in Unity 2022.3+. It computes indirect diffuse lighting from visible surfaces, emissive materials, and virtual emitters — with zero pre-computation and no baking required.

Key Features

• Real-time screen-space GI — indirect diffuse lighting without lightmaps or baking
• Near-field obscurance — built-in ambient occlusion at no extra cost
• Virtual emitters — inject GI from off-screen or hidden light sources
• Fallback system — reflection probes, reuse rays, and reflective shadow maps compensate for off-screen data
• Forward & deferred — works with both rendering paths (deferred recommended)
• Temporal filtering — motion-vector-based reprojection for stable, flicker-free results
• Volume system — global or local volumes to control GI per area
• 100% GPU-based — no CPU overhead, works with dynamic and procedural content

Requirements

How It Works

Global illumination refers to indirect diffuse lighting caused by light bouncing off surfaces. Unity's built-in lights (directional, spot, point) provide direct lighting. Radiant GI computes the indirect contribution in real time using screen-space ray marching:

1. For each pixel, one or more rays are marched through the depth buffer
2. When a ray hits a surface, the color at that point is gathered as indirect light
3. Results are denoised with spatial blur and temporal reprojection
4. The final GI contribution is composited onto the scene