I want to implement a building system. For units movement, I'm using NavigationPolygonInstance, with some "negative" areas where units cannot break through.
Each building type will have its own scene.
The problem is: what happens when a new building is created, a building scene is instanced? How do I edit the NavigationPolygonInstance to add a new "negative" area around the new building has been built, so units cannot break trough?
I thought I could create an NavigationPolygonInstance within the building scene, so both Navigation nodes (in the building scene and the parent scene (called Main)) could merge... but it's not working, so I'm running out of ideas.
Here's a pic of my project, the main building (red roof) and the farm are not instanced scenes, they are embedded in the Main scene.

I want to implement a building system. For units movement, I'm using NavigationPolygonInstance, with some "negative" areas where units cannot break through.
Each building type will have its own scene.
The problem is: what happens when a new building is created, a building scene is instanced? How do I edit the NavigationPolygonInstance to add a new "negative" area around the new building has been built, so units cannot break trough?
I thought I could create an NavigationPolygonInstance within the building scene, so both Navigation nodes (in the building scene and the parent scene (called Main)) could merge... but it's not working, so I'm running out of ideas.
Here's a pic of my project, the main building (red roof) and the farm are not instanced scenes, they are embedded in the Main scene.