Specifies the radius the Progressive Lightmapper uses to filter the ambient occlusion component in the lightmap when you use the Gaussian filter. (Editor only).
The value range is 0 through 5. The default value is 2. A higher value increases the strength of the blur, which reduces the amount of noise in the ambient occlusion component of the lightmap.
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 Filtering > Ambient Occlusion Filter > Radius property in the Lighting Settings Asset Inspector.
Additional resources: Lighting Settings Asset.