ARFace.swift

extension ViewController: ARSCNViewDelegate {
    
    func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {
        guard let faceAnchor = anchor as? ARFaceAnchor,
            let device = sceneView.device else { return nil }
        let faceGeometry = ARSCNFaceGeometry(device: device)
        let node = SCNNode(geometry: faceGeometry)
        node.geometry?.firstMaterial?.fillMode = .lines

        DispatchQueue.main.async {
            self.updateFeatures(for: node, using: faceAnchor)
        }
        
        return node
    }
    func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
        guard let faceAnchor = anchor as? ARFaceAnchor, let faceGeometry = node.geometry as? ARSCNFaceGeometry else { return }
        
        // 更新，臉部表情變化時的位置
        faceGeometry.update(from: faceAnchor.geometry)
        updateFeatures(for: node, using: faceAnchor)
    }
  
    func updateFeatures(for node: SCNNode, using anchor: ARFaceAnchor) {
        for (feature, indices) in zip(features, featureIndices) {
            let child = node.childNode(withName: feature, recursively: false) as? EmojiNode
            let vertices = indices.map { anchor.geometry.vertices[$0] }
            child?.updatePosition(for: vertices)
        }
    }
}