Non-directional, Directional or Directional Specular lightmaps rendering mode.
注意：该属性仅在构建玩家时序列化。在所有其他情况下，由 Unity 光照贴图系统（或带有外部光照贴图数据的自定义脚本）负责在进入场景加载或播放模式时进行设置。You can continue reading here if you want to know what the different lightmap modes do.