You can use the Enlighten Lighting Mode property to control how an actor interacts with indirect lighting.

This is an important way to optimize your level. It:

makes the precompute faster
reduces the latency of indirect lighting updates in game mode

Radiosity: include or exclude

You can choose whether or not to include each actor in Enlighten radiosity computations. Excluded actors have no effect on the indirect lighting result, but can still be lit by indirect lighting.

To speed up the precompute, choose to exclude actors that have no significant effect on the bounce lighting. See the Beginner tutorials for more information.

The actors in your level that have a fixed shape and position are static. The actors that can move during gameplay are non-static.

Actors that are static are included by default. For example:

large architectural features such as terrain and buildings
smaller props such as furniture, debris or foliage

Actors that are non-static are excluded by default. For example:

objects that move around the world during gameplay
objects that deform during gameplay, such as skeletal meshes

If an actor that moves during gameplay were included in Enlighten radiosity computations, the indirect lighting might look obviously incorrect.

Lighting: lightmaps or probes

You can choose to light each actor using either lightmaps or probes. Which method is best depends on the mesh.

To speed up the precompute, choose to use probe lighting for actors that cannot be lit efficiently using a lightmap. See the Beginner tutorials for more information.

Lightmaps provide efficient lighting for:

meshes with surface area (or groups of meshes with combined surface area) larger than the lightmap pixel size
meshes with simple topology easily unwrapped to a flat surface, such as terrain and buildings

Probes provide efficient lighting for:

meshes that are relatively small, and so can be lit effectively using a limited number of samples per mesh
meshes with complex topology that isn't easily unwrapped to a flat surface, such as foliage or body parts

Actors that move during gameplay are always lit using probes. Landscape and Geometry Brush actors are always lit using lightmaps.

Choose a lighting mode

To set the lighting mode for a mesh, under Details, under, use the Lighting Mode menu.

Lighting Mode	Lighting	Example use
Contribute Lightmap	Lightmaps	Simple meshes that reflect a noticeable amount of light, such as floors and walls
Contribute Probe	Probes	Complex meshes that reflect a noticeable amount of light, such as larger trees
Probe	Probes	Small meshes that don't reflect a noticeable amount of light, such as small furniture or decorative objects
Detail	Lightmaps¹	Meshes directly on surfaces, such as debris or posters (see Shared lightmaps)
Disabled	Sky lighting	Very distant background meshes

¹ Actors using the Detail lighting mode automatically share nearby lightmaps.

This applies to all standard actor types, including Static Mesh Actors, Landscape, Geometry Brushes, Instanced Foliage and Landscape Spline Meshes.

The set of lighting modes available is different depending on the type of actor.

Actor Type	Lighting Modes
Static Mesh Actor	All
Instanced Foliage	All except Contribute Lightmap
Landscape	Only Contribute Lightmap
Landscape Spline Mesh	All
Geometry Brush	Only Contribute Lightmap
other actors	Only Probe