A 2D polyline shape, intended for use in physics. Used internally in CollisionPolygon2D when it's in CollisionPolygon2D.BUILD_SEGMENTS mode.

Being just a collection of interconnected line segments, ConcavePolygonShape2D is the most freely configurable single 2D shape. It can be used to form polygons of any nature, or even shapes that don't enclose an area. However, ConcavePolygonShape2D is hollow even if the interconnected line segments do enclose an area, which often makes it unsuitable for physics or detection.

Warning: Physics bodies that are small have a chance to clip through this shape when moving fast. This happens because on one frame, the physics body may be on the "outside" of the shape, and on the next frame it may be "inside" it. ConcavePolygonShape2D is hollow, so it won't detect a collision.

Performance: Due to its complexity, ConcavePolygonShape2D is the slowest 2D collision shape to check collisions against. Its use should generally be limited to level geometry. If the polyline is closed, CollisionPolygon2D's CollisionPolygon2D.BUILD_SOLIDS mode can be used, which decomposes the polygon into convex ones; see ConvexPolygonShape2D's documentation for instructions.