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Concave polygon shape resource for 2D physics.
The shape consists of a collection of line segments, and as such it does not include any "inside" that the segments might be enclosing. If the segments do enclose anything, then the shape is hollow, as opposed to a ConvexPolygonShape2D which is solid. See also CollisionPolygon2D.
Being made out of line segments, this shape is the most freely configurable single 2D shape. It can be used to form (hollow) polygons of any nature, convex or concave.
Note: When used for collision, ConcavePolygonShape2D is intended to work with static PhysicsBody2D nodes like StaticBody2D and is not recommended to use with RigidBody2D nodes in a mode other than Static. A CollisionPolygon2D in convex decomposition mode (solids) or several convex objects are advised for that instead. Otherwise, a concave polygon 2D shape is better suited for static bodies.
Warning: The nature of this shape makes it extra prone to being tunneled through by (small) fast physics bodies. For example, consider a (small) rigid body Ball traveling toward a static body Box at high speed. If the box uses a ConcavePolygonShape2D consisting of four segments, then the ball might end up inside the box or tunnel all the way through the box, if it goes fast enough. This is (partly) because the ball can only collide against the individual segments of the hollow box. In interactions with rigid bodies tunneling can be avoided by enabling continuous collision detection on the rigid body.
Warning: Using this shape for an Area2D (via a CollisionShape2D node) may give unexpected results: the area will only detect collisions with the segments in the ConcavePolygonShape2D (and not with any "inside" of the shape, for example).
Performance: Due to its complexity, ConcavePolygonShape2D is the slowest collision shape to check collisions against. Its use should generally be limited to level geometry. For convex geometry, using ConvexPolygonShape2D will perform better. For dynamic physics bodies that need concave collision, several ConvexPolygonShape2Ds can be used to represent its collision by using convex decomposition; see ConvexPolygonShape2D's documentation for instructions. However, consider using primitive collision shapes such as CircleShape2D or RectangleShape2D first.
PackedVector2Array segments =
The array of points that make up the ConcavePolygonShape2D's line segments. The array (of length divisible by two) is naturally divided into pairs (one pair for each segment); each pair consists of the starting point of a segment and the endpoint of a segment.