Quick answer: Use Adaptive Probe Volumes (APV) or place dense light probes just inside walls to prevent interpolation from pulling outdoor probes into interior lighting.
An open-world game with house interiors shows characters lit by sunlight even inside dark rooms. Probes outside the wall interpolate through, illuminating moving objects as if windowed sunlight.
APV (Recommended)
URP 14+ / HDRP support Adaptive Probe Volumes:
- Add a Probe Volume to the scene.
- Set Subdivision per region (higher near walls/lights).
- Bake.
APV detects geometry boundaries and refines sampling there. Reduces leak dramatically vs traditional light probes.
Manual Probe Placement
For legacy projects without APV: place Light Probe Groups carefully.
- Probes just inside the room (1 unit from wall).
- Probes outside the room (1 unit out).
- Avoid sparse probes across walls — interpolation pulls through.
Place probes along corridors and entry thresholds densely; rooms can be sparser in the middle.
Light Probe Proxy Volume
For large objects (vehicle, big enemy), one probe sample is too coarse. Add Light Probe Proxy Volume component:
- Subdivides the object’s bounds, samples probes per cell.
- Better lighting variation across the object.
Light Probe Group Hierarchy
Group probes per room. Each room gets a Light Probe Group; gameplay logic doesn’t touch lighting. Bake all together — Unity merges into one tetrahedralization.
Verifying
Move a dynamic object across a wall boundary. Outside: lit by sunlight. Inside: lit by interior lights only. Light transition happens at the wall, not gradually. No phantom bright spots in interior.
“Probes don’t know about geometry. You teach them by placing carefully or using APV.”
For tightly enclosed scenes (corridors, dungeons), APV gives near-baked-quality dynamic lighting without manual probe tuning. Major QoL upgrade.