Combining baked lightmaps with lighting probes for moving objects

Plan for surfaces and movement

A room can have attractive baked walls while its moving character looks disconnected from them. Surface lightmaps and spatial lighting probes sample different domains. Treat both as part of the lighting design, and decide which scene elements are allowed to move or change after the bake.

Use a representative route through a doorway, beside a wall, and under an overhang before committing to a level-wide sample budget.

Understand the two representations

Lightmaps attach precomputed illumination to static surfaces through UV charts. Margins and atlas padding help keep unrelated charts from contaminating each other during sampling. [1]

Baked probes store lighting at positions in space; interpolation supplies an approximation for moving objects. [2] Volumetric approaches distribute samples through a region, with density and interpolation affecting both detail and leakage. Epic's implementation documents these accuracy and memory tradeoffs. [3] More surface texels do not automatically improve a character's spatial lighting samples.

Calculate a wall's sampling cost

Consider an illustrative wall 5 metres wide and 3 metres high. At 20 texels per metre, its ideal rectangular chart contains 100 × 60 = 6,000 texels. At 40 texels per metre, that becomes 200 × 120 = 24,000 texels: four times the area before padding, packing waste, and compression.

If the wall already looks smooth but the character brightens near a dark doorway, increasing that chart's resolution targets the wrong representation. Inspect which spatial samples influence the character and whether they cross a lighting boundary. This is a diagnostic example, not a recommended universal texel density.

Validate a complete bake

Freeze geometry and lighting intended to be static. Inspect lightmap UV overlap, chart scale, margins, and the baked atlas at the actual output resolution. Then visualize probe positions or cells and move a neutral test object along the gameplay route at several heights.

Compare its lighting with nearby surfaces, keeping exposure fixed. Inspect thin walls, corners, and transitions between streamed areas. Adjust sample placement or local density only where the failure appears, then measure the resulting data size. Include the final packaged build because missing or mismatched baked data can differ from an editor preview.

Respect the frozen assumptions

Baked lighting describes the geometry and light configuration used to compute it. Opening a previously baked closed door does not automatically recompute its indirect illumination. Probe interpolation also cannot guarantee sharp visibility boundaries through thin walls. [2][3]

Document how dynamic direct lights, shadows, reflections, and changing environments complement the bake. Preserve a reference route and asset settings so later scene edits trigger a deliberate rebuild or an explicit change in lighting strategy.

Sources

• [1] Introduction to Lightmap UVs — Unity Technologies.
• [2] Light Probes — Unity Technologies.
• [3] Volumetric Lightmaps — Epic Games.