Specifies the radius the Progressive Lightmapper uses to filter the direct lighting component of the lightmap when using Gaussian filter. (Editor only).
The default value is one. The value range is 0 to 5. A higher value increases the strength of the blur, reducing noise from direct light in the lightmap.
This setting affects lightmaps generated by the Baked Global Illumination system. It applies only when using the Progressive Lightmapper.
When Unity serializes this LightingSettings object as a Lighting Settings Asset, this property corresponds to the Filtering > Direct Filter > Radius property in the Lighting Settings Asset Inspector.
Additional resources: Lighting Settings Asset.