When you use lots of lightmap pixels or probes:

the Enlighten precompute takes longer
the Enlighten data becomes larger
the time between each lighting update increases

Fortunately, you don't need many pixels or probes to provide high-quality indirect lighting. A relatively small number is sufficient.

The Enlighten configuration for this level strikes a balance between accuracy and cost. The Enlighten Lighting Mode, Enlighten Quality and Enlighten probe resolution keep the number of lightmap pixels and probes small, while providing believable indirect lighting.

In large levels, certain configurations can result in a very large number of lightmap pixels, which might cause the precompute to take a long time.

Radiosity contribution

The level is configured to exclude actors which don't reflect a noticeable amount of light from the Enlighten computations. For example, light reflected by small or thin objects makes very little difference to the overall lighting effect, so they're not included. This reduces the Enlighten lighting complexity.

Make sure the View Mode is set to Lit.
From the Show menu, select Use Defaults to show the level with the default editor visualizations.
To see which actors are included in the Enlighten computations, in the Show menu, enable Enlighten > Radiosity Geometry.
Radiosity Geometry disabled Radiosity Geometry enabled
When Radiosity Geometry is enabled, small objects, such as drainpipes, lampposts, and sattelite dishes, are excluded from the editor view. These are the objects excluded from the Enlighten computations.
Disable Radiosity Geometry to show the small objects again.
In the World Outliner, double-click Props_LampPost01 to focus on it.
This actor isn't included in the Enlighten computations because it wouldn't reflect much light.
Change the view mode to Lighting Only.
Notice that the lighting around the actor is still believable, even though it reflects no light.
You can choose which actors are included in the Enlighten computations in the Details panel by changing the Enlighten Lighting Mode. This is described in the next tutorial.
From the Show menu, select Use Defaults to show the level normally again.
Re-enable Enlighten > Lighting Mode.
Only actors lit with lightmaps (orange) are included in the Enlighten computations.

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