如何在ARKit中自动调整3D文本的背景大小

import ARKit

class ViewController: UIViewController, ARSCNViewDelegate {
    
    @IBOutlet var sceneView: ARSCNView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 设置AR场景的代理
        sceneView.delegate = self
        
        // 创建一个3D文本对象
        let textNode = SCNNode()
        let textGeometry = SCNText(string: "Hello, ARKit!", extrusionDepth: 0.1)
        textNode.geometry = textGeometry
        
        // 设置文本的字体和大小
        textGeometry.font = UIFont(name: "Helvetica", size: 0.1)
        
        // 创建文本渲染器
        let textMaterial = SCNMaterial()
        textMaterial.diffuse.contents = UIColor.white
        textNode.geometry?.materials = [textMaterial]
        
        // 将文本对象添加到AR场景中
        sceneView.scene.rootNode.addChildNode(textNode)
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        // 配置AR场景追踪
        let configuration = ARWorldTrackingConfiguration()
        sceneView.session.run(configuration)
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        
        // 暂停AR场景追踪
        sceneView.session.pause()
    }
    
    func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
        // 获取文本对象的边界框大小
        guard let textNode = sceneView.scene.rootNode.childNode(withName: "textNode", recursively: true),
              let textGeometry = textNode.geometry as? SCNText else {
            return
        }
        
        let (min, max) = textGeometry.boundingBox
        let width = CGFloat(max.x - min.x)
        let height = CGFloat(max.y - min.y)
        
        // 调整文本对象的背景大小
        let backgroundNode = SCNNode(geometry: SCNPlane(width: width, height: height))
        backgroundNode.geometry?.firstMaterial?.diffuse.contents = UIColor.black.withAlphaComponent(0.5)
        backgroundNode.position = SCNVector3((max.x + min.x) / 2, (max.y + min.y) / 2, min.z - 0.01)
        
        // 将背景节点添加到文本节点上
        textNode.addChildNode(backgroundNode)
    }
}