# IKRig.Joint A definition of a rig joint and its IK solver settings. ``` struct Joint ``` ## Topics ### Structures [`struct ID`](/documentation/RealityKit/IKRig/Joint/ID-swift.struct) The identity type for a joint in a rig. [`struct LimitsDefinition`](/documentation/RealityKit/IKRig/Joint/LimitsDefinition) A definition of joint rotation limits. ### Initializers [`init(name: String, parentID: IKRig.Joint.ID?, restTransform: Transform)`](/documentation/RealityKit/IKRig/Joint/init(name:parentID:restTransform:)) Creates a joint with the provided base elements. ### Instance Properties [`var active: Bool`](/documentation/RealityKit/IKRig/Joint/active) A boolean value that sets whether the solver rotates the joint. [`var fkWeightPerAxis: SIMD3`](/documentation/RealityKit/IKRig/Joint/fkWeightPerAxis) The per-axis weight of the FK demand on the joint. [`var id: IKRig.Joint.ID`](/documentation/RealityKit/IKRig/Joint/id-swift.property) The identifier of the joint. [`var limits: IKRig.Joint.LimitsDefinition?`](/documentation/RealityKit/IKRig/Joint/limits) The per-axis rotation limits of the joint. [`let name: String`](/documentation/RealityKit/IKRig/Joint/name) The name of the joint. [`var parentID: IKRig.Joint.ID?`](/documentation/RealityKit/IKRig/Joint/parentID) The identifier of the parent joint if there is one. [`var restTransform: Transform`](/documentation/RealityKit/IKRig/Joint/restTransform) The local space transformation of the joint in the solver’s rest pose. [`var rotationStiffness: SIMD3`](/documentation/RealityKit/IKRig/Joint/rotationStiffness) The per-axis rotational stiffness of the joint. ## Relationships ### Conforms To [`Identifiable`](/documentation/Swift/Identifiable) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)