Show->Visualize->Volume Lighting Samples to visualize the lighting samples generated by Lightmass.
The goal with this workflow is to require as little content setup as possible. However, sometimes this placement heuristic
gives insufficient detail in areas that are floating in space, for example an elevator that characters ride on or a flying
section. You can place LightmassCharacterIndirectDetailVolumes around those areas to get more detail.
At runtime, the Indirect Lighting Cache will interpolate the lighting samples to positions around each movable object. A movable object is any component with Mobility set to Movable.
Here the torus is a movable Static Mesh and the 5x5x5 interpolation positions are shown.
This interpolation only happens when the object moves enough to invalidate it, hence the cache naming. Note that the positions
are quite far from the object's bounds. This is to provide continuous and stable lighting as the object moves through the world.
Most objects will effectively get 3x3x3 interpolation resolution. The volume lighting samples store directional indirect lighting which allows normal maps to work.