Specifies the number of samples the Progressive Lightmapper uses for direct lighting calculations. (Editor only).
The range is 1 to 1,000,000,000. Higher values result in reduced noise in lightmaps, but baking takes more time. The default value is 32.
This setting affects lightmaps generated by the Baked Global Illumination system. It only applies to the the Progressive Lightmapper.
When Unity serializes this LightingSettings object as a Lighting Settings Asset, this property corresponds to the Direct Samples property in the Lighting Settings Asset Inspector.
Additional resources: Lighting Settings Asset.