A joint used with [Skeleton2D] to control and animate other nodes. A hierarchy of [Bone2D]s can be bound to a [Skeleton2D] to control and animate other [Node2D] nodes. You can use [Bone2D] and [Skeleton2D] nodes to animate 2D meshes created with the [Polygon2D] UV editor. Each bone has a [member rest] transform that you can reset to with [method apply_rest]. These rest poses are relative to the bone's parent. If in the editor, you can set the rest pose of an entire skeleton using a menu option, from the code, you need to iterate over the bones to set their individual rest poses. Stores the node's current transforms in [member rest]. Returns whether this [Bone2D] is going to autocalculate its length and bone angle using its first [Bone2D] child node, if one exists. If there are no [Bone2D] children, then it cannot autocalculate these values and will print a warning. Returns the angle of the bone in the [Bone2D]. [b]Note:[/b] This is different from the [Bone2D]'s rotation. The bone's angle is the rotation of the bone shown by the gizmo, which is unaffected by the [Bone2D]'s [member Node2D.transform]. Returns the node's index as part of the entire skeleton. See [Skeleton2D]. Returns the length of the bone in the [Bone2D] node. Returns the node's [member rest] [Transform2D] if it doesn't have a parent, or its rest pose relative to its parent. When set to [code]true[/code], the [Bone2D] node will attempt to automatically calculate the bone angle and length using the first child [Bone2D] node, if one exists. If none exist, the [Bone2D] cannot automatically calculate these values and will print a warning. Sets the bone angle for the [Bone2D]. This is typically set to the rotation from the [Bone2D] to a child [Bone2D] node. [b]Note:[/b] This is different from the [Bone2D]'s rotation. The bone's angle is the rotation of the bone shown by the gizmo, which is unaffected by the [Bone2D]'s [member Node2D.transform]. Sets the length of the bone in the [Bone2D]. Rest transform of the bone. You can reset the node's transforms to this value using [method apply_rest].