Lightmaps
LightmapsLightmaps store baked illumination in textures mapped onto a mesh. A dedicated UV layout assigns surface regions to separate texture charts, with enough padding to keep filtering from mixing unrelated surfaces. Resolution determines how many texels are available to represent lighting detail: too little can blur shadows, while unnecessarily high values increase bake time, storage, and memory.
Good lightmap UVs and sufficient sampling solve different problems. A larger texture cannot fix overlapping charts, and more GI samples cannot give a low-resolution lightmap finer spatial detail.
Features > Lightmaps contains two separate tools: Generate edits shared mesh UV assets, while Set Resolution edits selected scene-component resolution overrides.
These changes prepare the next bake. They do not regenerate saved lighting by themselves.
Generate: selection and UV settings
Selection
Default: Selected Content Browser assets.
Chooses where Generate finds static meshes:
- Selected Content Browser assets uses selected static-mesh assets.
- Selected scene objects collects static meshes from selected actors/components.
Shared mesh assets are processed once even when multiple selected instances use them. This selector does not change the selection source of Set Resolution, which always uses scene objects.
Destination
Default: 1. Range: 0 to 7.
UV channel to replace with generated lightmap UVs. The tool also assigns it as the asset's lightmap coordinate index, so baking knows which channel to use.
Channel 0 commonly contains material UVs. Replacing it can change how the mesh's materials map onto the surface. Choose a channel whose contents can be replaced and remember that editing the asset affects all instances using it.
Resolution
Default: 128. Choices: powers of two from 32 to 4096.
Packing target used when generating the UV layout. It is also assigned as the mesh asset's lightmap resolution. Existing per-component resolution overrides are retained, so an instance can still bake at a different resolution.
Higher values provide more packing pixels, but do not automatically remove an instance's lower override.
Chart Padding
Default: 4. Range: 1 to 32 pixels.
Gap between UV islands measured at the packing Resolution. Padding helps keep filtering from mixing unrelated charts. More padding leaves less space for the charts themselves.
Keep the actual bake resolution at least as high as the packing target to retain that pixel gap. Baking at half the target reduces the output-pixel padding too.
Generate
Creates the UV layout for eligible selected mesh assets and assigns the destination and asset resolution. The button is unavailable during play or without a valid selection.
Generation can be cancelled. Already processed assets remain changed; cancellation does not roll back the entire batch. Review skipped/failed meshes in the Output Log, save the assets you intend to keep, and rebake lighting that used the previous layout.
Set Resolution: scene density
Texels per Meter
Default: 64. Minimum: 0.001; normal slider range: 1 to 128.
Requested lightmap density in world space. A texel is one lightmap texture sample. More texels per meter can capture smaller lighting detail but require larger maps and more bake work.
The preview calculates resolutions for the current scene selection. If the largest object would exceed 4096, the tool reduces the common density for the whole processed selection to preserve relative detail.
This is a requested average density, not a guarantee that every triangle has identical local density. UV distortion still matters.
Resolution preview
The output reports the resulting resolution range, maximum usable density, and skipped objects. A limited indication means the requested density could not be applied unchanged because of the resolution limit.
Waiting for mesh compilation... means the tool is waiting for mesh data. Select scene meshes means there is no suitable selection. Resolve the message rather than repeatedly applying the same settings.
Set Resolution
Applies lightmap resolution overrides to eligible selected static scene mesh components. It does not generate UVs or change the shared mesh asset's default resolution.
Results are constrained to 4 through 4096 and rounded in multiples of four. Some small objects therefore reach the minimum instead of matching an arbitrarily low target exactly.
The result distinguishes updated components, already matching components, and skipped components. As with Generate, cancelling a batch can leave completed changes in place.
Use Generate for the mesh asset's UV layout. Use Set Resolution for the scene instances' density. Run a new lighting bake after either changes lighting inputs.
See UVs and density for troubleshooting and Lightmap storage for bake-wide scale, packing, and compression.