Line of sight can be set when you take a snapshot. When you take a snapshot, a list of access points is presented with varying signal strengths. Each access point has a checkbox in front of it's name/mac address. Check the checkbox of the access point(s) with a clear line of sight.
Let's say that you have created a representation of your office floor. You've added all the workplaces, and you have added the five access points to your floor.
In order for triangulation to work, you need to take snapshots:
-- at least one snapshot with a clear line of sight to each access point. Snapshots with clear line of sight are used to determine the signal strength of each access point.
-- and at least one snapshot in each room. Snapshots without clear line of sight are used to determine signal degradation of each access point in each room.
These snapshots combined allow for localization by triangulation anywhere on your floor.