上一節範例程式列印到主控台的資訊，包含 Y Bot 機器人模型的所有關節名稱，共有65個關節，內容如下：

機器人關節名稱65
[
"mixamorig_Hips",
"mixamorig_Hips/mixamorig_Spine",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_Neck",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_Neck/mixamorig_Head",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_Neck/mixamorig_Head/mixamorig_HeadTop_End",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandThumb1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandThumb1/mixamorig_LeftHandThumb2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandThumb1/mixamorig_LeftHandThumb2/mixamorig_LeftHandThumb3",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandThumb1/mixamorig_LeftHandThumb2/mixamorig_LeftHandThumb3/mixamorig_LeftHandThumb4",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandIndex1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandIndex1/mixamorig_LeftHandIndex2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandIndex1/mixamorig_LeftHandIndex2/mixamorig_LeftHandIndex3",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandIndex1/mixamorig_LeftHandIndex2/mixamorig_LeftHandIndex3/mixamorig_LeftHandIndex4",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandMiddle1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandMiddle1/mixamorig_LeftHandMiddle2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandMiddle1/mixamorig_LeftHandMiddle2/mixamorig_LeftHandMiddle3",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandMiddle1/mixamorig_LeftHandMiddle2/mixamorig_LeftHandMiddle3/mixamorig_LeftHandMiddle4",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandRing1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandRing1/mixamorig_LeftHandRing2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandRing1/mixamorig_LeftHandRing2/mixamorig_LeftHandRing3",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandRing1/mixamorig_LeftHandRing2/mixamorig_LeftHandRing3/mixamorig_LeftHandRing4",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandPinky1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandPinky1/mixamorig_LeftHandPinky2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandPinky1/mixamorig_LeftHandPinky2/mixamorig_LeftHandPinky3",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_LeftShoulder/mixamorig_LeftArm/mixamorig_LeftForeArm/mixamorig_LeftHand/mixamorig_LeftHandPinky1/mixamorig_LeftHandPinky2/mixamorig_LeftHandPinky3/mixamorig_LeftHandPinky4",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandThumb1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandThumb1/mixamorig_RightHandThumb2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandThumb1/mixamorig_RightHandThumb2/mixamorig_RightHandThumb3",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandThumb1/mixamorig_RightHandThumb2/mixamorig_RightHandThumb3/mixamorig_RightHandThumb4",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandIndex1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandIndex1/mixamorig_RightHandIndex2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandIndex1/mixamorig_RightHandIndex2/mixamorig_RightHandIndex3",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandIndex1/mixamorig_RightHandIndex2/mixamorig_RightHandIndex3/mixamorig_RightHandIndex4",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandMiddle1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandMiddle1/mixamorig_RightHandMiddle2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandMiddle1/mixamorig_RightHandMiddle2/mixamorig_RightHandMiddle3",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandMiddle1/mixamorig_RightHandMiddle2/mixamorig_RightHandMiddle3/mixamorig_RightHandMiddle4",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandRing1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandRing1/mixamorig_RightHandRing2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandRing1/mixamorig_RightHandRing2/mixamorig_RightHandRing3",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandRing1/mixamorig_RightHandRing2/mixamorig_RightHandRing3/mixamorig_RightHandRing4",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandPinky1",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandPinky1/mixamorig_RightHandPinky2",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandPinky1/mixamorig_RightHandPinky2/mixamorig_RightHandPinky3",
"mixamorig_Hips/mixamorig_Spine/mixamorig_Spine1/mixamorig_Spine2/mixamorig_RightShoulder/mixamorig_RightArm/mixamorig_RightForeArm/mixamorig_RightHand/mixamorig_RightHandPinky1/mixamorig_RightHandPinky2/mixamorig_RightHandPinky3/mixamorig_RightHandPinky4",
"mixamorig_Hips/mixamorig_LeftUpLeg",
"mixamorig_Hips/mixamorig_LeftUpLeg/mixamorig_LeftLeg",
"mixamorig_Hips/mixamorig_LeftUpLeg/mixamorig_LeftLeg/mixamorig_LeftFoot",
"mixamorig_Hips/mixamorig_LeftUpLeg/mixamorig_LeftLeg/mixamorig_LeftFoot/mixamorig_LeftToeBase",
"mixamorig_Hips/mixamorig_LeftUpLeg/mixamorig_LeftLeg/mixamorig_LeftFoot/mixamorig_LeftToeBase/mixamorig_LeftToe_End",
"mixamorig_Hips/mixamorig_RightUpLeg",
"mixamorig_Hips/mixamorig_RightUpLeg/mixamorig_RightLeg",
"mixamorig_Hips/mixamorig_RightUpLeg/mixamorig_RightLeg/mixamorig_RightFoot",
"mixamorig_Hips/mixamorig_RightUpLeg/mixamorig_RightLeg/mixamorig_RightFoot/mixamorig_RightToeBase",
"mixamorig_Hips/mixamorig_RightUpLeg/mixamorig_RightLeg/mixamorig_RightFoot/mixamorig_RightToeBase/mixamorig_RightToe_End"
]

這是從「print(機器人模型.jointNames)」得到的內容，可以看得出來：

  1. jointNames 資料類型是「字串陣列」
  2. 字串內容實際上是完整的關節路徑，路徑包含所有上層關節，名稱用 “/” 分開
  3. 所有關節形成一個樹狀目錄，最上層的根節點是 mixamorig_Hips （臀部）
  4. 整個骨骼系統包含65個關節，對應65個路徑名稱

若將關節名稱加註到圖片中，會更容易看清楚，如下：

截圖 2025-09-03 下午5.00.45.png

從關節分布可看得出來，手掌關節最精細，兩手共46個關節（佔總數70%）；其他頭、頸、肩、脊椎、腿、腳掌合計才19個關節，相對簡略。由此推論，這個機器人手部動作最靈活，肢體動作也還行，但無法開口、眨眼或做任何臉部表情。

如何操縱這些關節呢？

我們得先了解關節的屬性（參考原廠文件）：

// MeshResource.Skeleton.Joint
init(
    name: String,
    parentIndex: Int?,    // nil for root joint
    inverseBindPoseMatrix: simd_float4x4,
    restPoseTransform: Transform
)

模型關節只有4個屬性，除了名稱(name)、父關節索引(parentIndex)之外，restPoseTransform 是靜止姿勢的座標變換，inverseBindPoseMatrix 是目前姿勢的反矩陣。為什麼叫 Pose (姿勢）下節說明。

還記得上一課的幾何連接點(GeometricPin)嗎？幾何連接點的主要屬性(position, orientation)就是一個座標變換，用來設定連接點的位置與旋轉面向。