如何使 UILabel 在未被跟踪图像时显示在屏幕上，并在跟踪图像时消失

Question

我正在使用ARKit制作一个图像识别应用程序，用户将相机指向空间中的几个不同图像，视频将在这些图像上播放。我创建了带有消息的UILabel，以便向用户提供说明。当用户第一次打开应用程序时，我想向他们显示一条消息，告诉他们将相机指向图像。每当相机跟踪图像时，我都希望UILabel消失。

在我的代码中，当跟踪图像时，我可以让标签消失，但一旦不再跟踪图像，我就无法让它重新出现。

extension ViewController: ARSCNViewDelegate {
func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: 
ARAnchor) -> SCNNode? {
let node = SCNNode()
//Show video overlayed to image
if let imageAnchor = anchor as? ARImageAnchor{
DispatchQueue.main.async { self.messageView?.isHidden = 
true }
let plane = SCNPlane(width: 
imageAnchor.referenceImage.physicalSize.width, height: 
imageAnchor.referenceImage.physicalSize.height)
//Create Plane
switch imageAnchor.referenceImage.name!{
case "slaveAuction":
//Set AVPlayer as the planes texture and play
plane.firstMaterial?.diffuse.contents = 
self.slaveAuction
self.slaveAuction.play()
case "columbus":
plane.firstMaterial?.diffuse.contents = 
self.columbus
self.columbus.play()
case "isabellasCourt":
plane.firstMaterial?.diffuse.contents = 
self.isabellasCourt
self.isabellasCourt.play()
case "hawksbell":
plane.firstMaterial?.diffuse.contents = 
self.hawksbell
self.hawksbell.play()
default:
print("Images not found")
}
let planeNode = SCNNode(geometry: plane)
// Rotate the plane to match the anchor
planeNode.eulerAngles.x = -.pi/2
// Add plane node to parent
node.addChildNode(planeNode)
}
return node
}
}

当我不跟踪图像时，我需要帮助使消息视图显示出来。

Answer 1

使planeNode类变为变量。并检查节点是否在每帧都可见。

func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
if let pointOfView = sceneView.pointOfView, planeNode != nil {
let isMaybeVisible = sceneView.isNode(planeNode, insideFrustumOf: pointOfView)
DispatchQueue.main.async {
if isMaybeVisible{
self.messageView.isHidden = true
}else{
self.messageView.isHidden = false
}
}
}
}

参见isNode(_：内部FrustumOf：)