What causes light probe seams on a character mesh?

Each renderer samples one tetrahedron of the probe network at its bounds center and applies that lighting to the whole mesh. When a large character mesh straddles a high-contrast probe boundary (sunlight to shadow), the entire body pops between two lighting values as the center crosses the boundary.

What is a Light Probe Proxy Volume?

LPPV samples the probe network at multiple points across the mesh's bounding volume rather than at a single center point. Lighting interpolates smoothly across the mesh and the seam disappears. Enable it via the Mesh Renderer's Light Probes dropdown.

How dense should my probe placement be?

Pack probes tightly across lighting boundaries (shadow edges, doorways, corners), and sparsely across uniform regions. The point of probes is interpolation; placing them where light gradient is smooth wastes bake time without improving quality.

Fix: Unity Light Probe Seams Visible on Baked Meshes

Quick answer: Densify your Light Probe Group around high-contrast lighting boundaries (shadow edges, doorways) and enable a Light Probe Proxy Volume on any renderer larger than the probe spacing. Single-sample probes always seam on big meshes.

Your character walks across the floor and her body suddenly goes dark mid-step. Or two pieces of identical scenery, an inch apart, are obviously different brightnesses. Light probe seams are showing through, and the answer is more probes plus an LPPV.

The Symptom

Dynamic or non-lightmapped meshes show a hard band where lighting changes abruptly. Walking across the band, the entire mesh pops from one lighting state to another. The boundary follows the geometry of the probe tetrahedralization rather than anything in the actual scene.

What Causes This

Light probes are sampled per renderer, at the renderer’s bounds center. The probe network is tetrahedralized; the sample point falls into one tetrahedron and the lighting is interpolated from that tetrahedron’s four corner probes. When the renderer’s center crosses a tetrahedron boundary, the four corner probes change — sometimes drastically — and the whole mesh pops.

The Fix

Step 1: Densify probes across lighting boundaries. Open your Light Probe Group. Add probes along every shadow edge, doorway, window cast, and indoor/outdoor transition. Keep probe spacing tighter than the smallest visual lighting change you care about.

// Rough rule of thumb
indoor uniform region:    one probe per ~3 m
shadow boundary:          probes every ~0.5 m along the line
doorway:                  probes inside, in plane, outside
character height range:   probes at floor and at head height

Step 2: Enable Light Probe Proxy Volume on big meshes. On any Mesh Renderer that is large compared to your probe spacing (terrain, large props, big characters), set Light Probes → Use Proxy Volume. Add a LightProbeProxyVolume component on the same GameObject. The mesh now samples the probe network at a 3D grid of points across its bounds and interpolates per-fragment.

Step 3: Re-bake. Window → Rendering → Lighting → Generate Lighting. Probe data is part of the bake; new probes are sampled here.

LPPV Settings That Matter

Resolution Mode = Custom. Set explicit X/Y/Z probe counts for the volume. 4×4×4 is plenty for most characters.
Bounding Box Mode = Automatic Local. Tracks the renderer’s bounds.
Probe Position Mode = Cell Corner. Sample at corners; interpolate inside.

Why Static Meshes Should Be Lightmapped, Not Probed

Probes are for dynamic or movable geometry. A static prop should be marked Contribute GI in the lightmapping settings; it then receives baked direct lighting per-texel and probes are irrelevant to it. If you see seams on a clearly static mesh, check that it has a lightmap UV channel and is marked Contribute GI → Lightmap.

Verifying It Worked

Window → Rendering → Light Probe Visualizer (or use the Lighting Window’s Probe Visualization mode). Walk a test object across the boundary in Play Mode; lighting should now interpolate smoothly. Toggle the LPPV on and off to compare.

“Probes where light changes. LPPV on big meshes. Lightmaps on static. Seams disappear.”

Related Issues

For reflection probe staleness, see reflection probe runtime. For static lightmap UV problems, see lightmap UV overlap.

Densify probes. Add LPPV. Re-bake. The lighting becomes one smooth gradient.