Determines the degree to which direct lighting is considered when calculating ambient occlusion in lightmaps. (Editor only).
Ambient occlusion (AO) is an effect that approximates how much ambient light a given point on a surface receives. When you apply AO to a Scene, areas of concavity - such as creases, holes and adjacent surfaces - appear darker.
This property determines how much direct lighting contributes to ambient occlusion calculations. Note that AO using direct lighting is not correct; the effect is intended to give the impression of occlusion from indirect lighting which is more diffuse. However it a can be used to achieve specific art styles.
The range is 0 through 10. The default value is 0. Higher values result in occluded areas becoming increasingly darker.
This setting affects lightmaps generated by the Baked Global Illumination system. Note that this property relates only to baked AO, and has no effect on any real-time AO post-processing effects.
When Unity serializes this LightingSettings object as a Lighting Settings Asset, this property corresponds to the Ambient Occlusion > Direct Contribution property in the Lighting Settings Asset Inspector.
Additional resources: Lighting Settings Asset, aoExponentIndirect.