How do you estimate how much daylight a patio cover will take from the room behind it?

The structural questions around a patio cover are fairly easy to list: attachment, footings, wind load, drainage, and permits. The daylight question seems much harder to judge before anything is built.

A roof that looks open and bright from the yard can still turn the kitchen or living room behind it noticeably darker, especially when the cover is deep or sits above a wide glass door. Seasonal sun angles probably make a simple answer even harder.

This came up while I was comparing photos from a FlexPatio project with the room directly behind the covered area. The outdoor space looked comfortable, but a finished exterior photo offered almost no clue about the indoor light change.

Before approving a design, is there a practical way contractors estimate that effect—temporary shade cloth, a sun-path app, a basic daylight study, or something else? What would you ask to see before signing off?