Base class for all objects affected by physics in 3D space. PhysicsBody is an abstract base class for implementing a physics body. All *Body types inherit from it. Adds a body to the list of bodies that this body can't collide with. Removes a body from the list of bodies that this body can't collide with. The physics layers this area is in. Collidable objects can exist in any of 32 different layers. These layers work like a tagging system, and are not visual. A collidable can use these layers to select with which objects it can collide, using the collision_mask property. A contact is detected if object A is in any of the layers that object B scans, or object B is in any layer scanned by object A. The physics layers this area can scan for collisions.