swift - 如何使 UILabel 在未跟踪图像时出现在屏幕上，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，告诉他们将相机对准图像。每当相机跟踪图像时，我希望 UILabel 消失。

在我的代码中，我得到了它，当跟踪图像时，我可以使标签消失，但是一旦我不再跟踪图像，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
    }

}

我需要帮助，以便在不跟踪图像时显示消息 View 。

Answer 1

使你的planeNode类变量。并检查您的节点是否每帧都可见。

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
            }
        }
    }
}

并参见 isNode(_:insideFrustumOf:)