Performance Tips

intermediate performance

Radiant GI (URP) · Troubleshooting & FAQ

Overview

Radiant GI is designed to be efficient — it runs entirely on the GPU with no pre-computation. However, real-time GI is inherently demanding. These tips help you find the right quality/performance balance for your target platform.

Recommended Baseline Configuration

The following settings provide a good balance for mid-range hardware (similar to the included Atrium demo scene):

Setting	Recommended Value	Notes
Indirect Intensity	`1`–`3`	Start low and increase to taste
Ray Count	`1`	Each additional ray significantly increases cost
Max Distance	`8`	Keep as low as your scene allows
Max Samples	`24`	`24`–`32` is the sweet spot
Thickness	`0.1`–`0.3`	Lower = more precise but more misses
Raymarch Accuracy	`8`	Reduce to improve performance
Downsampling	`1`	Increase to `2` for significant FPS gains
Reuse Rays	`0`–`0.5`	Cheap way to fill in missing data
Temporal Stability	`8`–`12`	Higher = smoother but slower response
Response Speed	`12`	Balance between ghosting and stability

Optimization Checklist

Optimization	Impact	Details
Reduce Ray Count	High	Going from 2 rays to 1 roughly halves GI computation cost. One ray is enough for compelling results in most scenes.
Increase Downsampling	High	Setting downsampling to `2` processes the GI at half resolution — major FPS improvement with a subtle quality reduction.
Lower Raymarch Accuracy	Medium	Effectively downscales the depth buffer for better GPU cache performance. Reduces precision slightly.
Reduce Max Distance	Medium	Shorter rays = fewer samples = faster. Set to the minimum that covers your room/area.
Reduce Max Samples	Medium	Fewer ray-march steps per ray. `24` is a good default; going lower than `16` may cause visible artifacts.
Use Deferred Rendering	Quality	Deferred provides g-buffer data (albedo, specular) for free, producing better results than forward rendering where this data must be approximated.
Enable Temporal Filter	Quality	Temporal accumulation smooths the noisy single-ray result over multiple frames, allowing you to use fewer rays while maintaining visual quality.
Bypass Post Processing	Low	Enable Ignore Post Processing in the Renderer Feature and disable post-processing on the camera to save a full-screen blit.
Use Local Volumes	Variable	Apply GI only where needed (indoors, key areas) and disable it in open areas where the effect is less noticeable.

Quality Tiers

Consider creating multiple Volume profiles for different hardware:

Tier	Ray Count	Downsampling	Max Samples	Fallbacks
Low	1	2	16	Reuse Rays only
Medium	1	1	24	Reuse Rays + APV/Sky
High	2	1	32	All fallbacks

Profiling tip: Use Unity's Frame Debugger (Window > Analysis > Frame Debugger) to identify which Radiant passes consume the most time. The Debug View in Radiant's settings also helps visualize individual buffers.

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