# 8. Lighting Pitfalls Part of [[Lighting and Baking]]. Previous: [[7.Worked Example Interior Exterior Checklist]]. ## 8.1 Double lighting **Symptom:** Static objects look blown out; Mixed light appears "added twice." **Causes** - Light Mode Mixed/Baked but Lighting Mode / subtractive expectations misunderstood — statics already store direct in Subtractive lightmaps while you also expect full realtime direct. - Emissive materials contributing to GI **and** a duplicate realtime light in the same place. - Reflection probe Intensity and material specular stacked with an overly bright Environment Reflections intensity. **Fix:** Pick one source of direct light per surface type; rebuild after Mode changes; reset Indirect Intensity / probe Intensity to 1 before art-directing. ## 8.2 Missing or empty probes **Symptom:** Dynamic objects go black, grey, or ignore the room's bounce when entering interiors. **Causes** - No LightProbeGroup / APV baked data. - Receive Global Illumination still set to Lightmaps on a dynamic object (no atlas entry → wrong/fallback lighting). - Probes left inside walls; tetrahedral volume does not cover the play space. - URP Asset still on Legacy probes while you only added an APV (or the reverse). **Fix:** Part 4 checklist; doorway density; verify Receive = Light Probes on dynamics. ## 8.3 Pink lightmaps / magenta materials **Symptom:** Magenta meshes after bake or on device. **Causes** - Shader does not support lightmaps / URP (wrong pipeline shader) — see [[URP Shaders and Shader Graph]]. - Lightmap textures stripped or Addressables/bundle path missing in player builds. - LOD group referencing a renderer that never received UV2 / GI flags. **Fix:** Confirm URP Lit (or Shader Graph with GI nodes) on all Contribute-GI meshes; include lightmap data in builds; rebake after LOD setup. ## 8.4 UV streaks, black edges, chart bleed **Causes:** Overlapping UV2, insufficient padding, extreme Scale in Lightmap mismatches, backface sampling. **Fix:** Part 3 — regenerate UVs, raise Lightmap Padding, adjust Lightmap Parameters backface tolerance / pushoff, do not "fix" with only sample counts. ## 8.5 Noisy lightmaps that never clean up **Causes:** Too few Indirect/Environment samples for an HDR sky or emissive interior; denoiser off; GPU tiling thrashing. **Fix:** Raise samples intelligently; enable Filtering Auto/Advanced; reduce resolution; free VRAM (part 2). ## 8.6 Light leaks (especially APV) **Causes:** Thin walls, probes seeing both sides, missing Contribute GI on occluders. **Fix:** Thicken geometry; Probe Adjustment Volumes; APV rendering layer masks per Unity docs; rebake. ## 8.7 Reflection probe "wrong room" **Causes:** Box Size too large (sees outside); Importance fights; Realtime probe stale; Box Projection disabled in URP Asset. **Fix:** Fit boxes per room; bake after lighting; enable Box Projection on asset + probe. ## 8.8 Additive scenes disagree **Causes:** Different Lighting Settings / Directional Mode across additively loaded scenes (Manual warns Directional Mode must match). **Fix:** Shared Lighting Settings asset; same Directional Mode even for UI/loading scenes that load additively. ## 8.9 Quest overdraw from lights **Symptom:** GPU bound in bright rooms with few triangles. **Causes:** Many realtime additional lights; realtime shadows; realtime reflection probes; huge additive particles lit by those lights. **Fix:** Part 6 — bake, cut lights, shorten Shadow Distance, baked probes only; measure with [[5.Quest 2 Performance and Rendering]]. ## 8.10 Auto Generate surprises **Symptom:** Editor hitching; inconsistent CI builds; lightmaps churn while you edit meshes. **Fix:** Disable Auto Generate for production; bake deliberately; commit Lighting Data Asset / lightmaps with clear version-control rules *(exact asset types to commit depend on your team's GI workflow — document them)*. ## 8.11 Quick triage table | Symptom | First place to look | |---|---| | Flat ambient everywhere | Environment lighting / sky intensity; probes missing | | Only statics look good | Dynamics not on Light Probes / APV | | Blotchy dark patches | UVs, backfaces, leaks, low samples | | Magenta | Shader / pipeline / missing lightmap assets | | Good in Editor, dark on Quest | Stripped lightmaps; Quality tier; wrong URP asset on device | | Doorway hard seam | Probe density; lightmap texel density on trim; leak | Return to hub: [[Lighting and Baking]].