Physics layers and navigation regions

Physics layers

Current physics layers are:

1. Environment: Anything in the environment that the player should collide with and get stopped by
   1. The player and the over-the-shoulder camera will collide with these
2. Player: The player is on their own layer
3. Walls: Anything that the overhead camera should interact with
   1. In general, all Walls should also be in the Environment group
   2. Props that the player might hide behind (i.e. pillars) should be in Envrionment but not Walls
      1. This way, when the player has the overhead camera active and they move behind something, the camera doesn't "snap" in front of the object
4. Pickups: Things that the player can pick up
   1. The player has a shapecast on them that checks for this

Navigation regions

Meshes that should be part of the navigation mesh must be added to the navigation_mesh_source_group group. This is a global group that should 

Navigation regions should be set to have their "Source Geometry Mode" set to "Group Explicit". This makes it so that only nodes in the navigation_mesh_source_group group get parsed as part of navigation mesh baking: