The maximum size in pixels of an individual lightmap texture. (Editor only).
The default value is 1024. Values are squared, so a value of 1024 results in a maximum resolution of 1024 x 1024. Smaller lightmaps might also be generated instead. This happens if it is possible to fit the required UVs into a smaller texture.
This setting affects lightmaps generated by the Baked Global Illumination system.
When Unity serializes this LightingSettings object as a Lighting Settings Asset, this property corresponds to the Max Lightmap Size property in the Lighting Settings Asset Inspector.
Additional resources: Lighting Settings Asset.