public LightmapsMode directionalityMode { get; set; }

When this is set to , Unity generates an additional lightmap that encodes a vector for the dominant direction of incoming light at each texel’s position. When this is set to /Non-Directional/, Unity does not generate these additional lightmaps.

The use of directional lightmaps can improve the rendering of normal mapped materials, but at the cost of increased storage and memory.

Directional lightmaps cannot be decoded on SM2.0 hardware; in these cases, Unity falls back to using non-directional lightmaps.

This property determines whether the next bake will produce directional or non-directional lightmaps. You can access whether the previous bake produced directional or non-directional lightmaps using the LightmapSettings.lightmapsMode property.

This setting affects lightmaps generated by the Baked Global Illumination system.

When Unity serializes this object as a Lighting Settings Asset, this property corresponds to the Directional Mode property in the Lighting Settings Asset Inspector.

Additional Resources: Lighting Settings Asset,Directional lightmapping.