Working on navigation mesh for AI, this is generated automatically, by selecting an area with a mouse. I'm using Clipper library for this. You can notice the offset from the inner polygons :
Didn't know how to connect vertices in the navigation mesh, so I triangulated it with Poly2Tri and used triangles to form connections. I will have to ditch Poly2Tri for some library that generates polygons instead, and do some "path smoothing"; starting from the yellow node, the node 10 is visible from 5 and should be directly connected in the final path.
In a platformer game this could be used for flying enemies. Triangles/polygons will be used to know in which area the entity and its target is located, so I can quickly get the nodes nearby, connect with them with a temporary node and calculate the final path.