在原本是world的地方改成 ARFaceTrackingConfiguration()

    var sceneView: ARSCNView!
    sceneView = ARSCNView(frame: view.frame)
    view.addSubview(sceneView)

    let configuration = ARFaceTrackingConfiguration()
    session.run(configuration)
    session.delegate = self
    
    func updateFaceFeatures(for faceAnchor: ARFaceAnchor) {
    let blendShapes = faceAnchor.blendShapes
    
    // 偵測特定的面部表情
    if let smileLeft = blendShapes[.mouthSmileLeft]?.floatValue, let smileRight = blendShapes[.mouthSmileRight]?.floatValue {
        let isSmiling = (smileLeft + smileRight) / 2.0 > 0.5
        print("笑容偵測: \(isSmiling)")
    }
    
    if let eyeBlinkLeft = blendShapes[.eyeBlinkLeft]?.floatValue, let eyeBlinkRight = blendShapes[.eyeBlinkRight]?.floatValue {
        let isWinking = (eyeBlinkLeft > 0.5 || eyeBlinkRight > 0.5)
        print("眨眼偵測: \(isWinking)")
    }
    
}

接著在ARSessionDelegate裡增加

func session(_ session: ARSession, didUpdate anchors: [ARAnchor]) {
    for anchor in anchors {
        guard let faceAnchor = anchor as? ARFaceAnchor else { continue }
        updateFaceFeatures(for: faceAnchor)
    }
}