Checked with version: 2018.1
Optimizing Scene lighting is not an exact science - your process usually depends on your artistic direction. There are many parts to creating a pleasing ambiance, and it can depend heavily on the project and its unique architecture, including whether the project uses single Scenes, Multi-Scene editing, or additive loading. For this reason, this document provides many different approaches, rather than one recommended workflow. The following sections, in particular, contain good advice on this subject:
When you start a new project, apply the following settings to use multiple Scenes correctly and achieve a smooth lighting workflow:
Enable Auto Generate only with single Scenes (see the next section, Auto Generate and Generate Lighting ).
Do not mix Scenes with Auto Generate enabled and Scenes that have Auto Generate disabled.
Whether using Multi-Scene editing or additive loading, ensure that all Scenes used together have identical Lighting Settings, with a focus on Global Settings.
If you are interested in making great visuals in Unity, see the Making believable visuals in Unity best practice guide.