Question

我正在为我的应用程序使用ARKit，并尝试从我的Web服务器（URL）动态加载.scn文件

这是我的代码的一部分

 let urlString = "https://da5645f1.ngrok.io/mug.scn"
        let url = URL.init(string: urlString)
        let request = URLRequest(url: url!)
        let session = URLSession.shared
        let downloadTask = session.downloadTask(with: request,
                completionHandler: { (location:URL?, response:URLResponse?, error:Error?)
                -> Void in
                print("location:\(String(describing: location))")
                let locationPath = location!.path
                let documents:String = NSHomeDirectory() + "/Documents/mug.scn"
                ls = NSHomeDirectory() + "/Documents"
                let fileManager = FileManager.default
                if (fileManager.fileExists(atPath: documents)){
                     try! fileManager.removeItem(atPath: documents)
                }
                try! fileManager.moveItem(atPath: locationPath, toPath: documents)
                print("new location:\(documents)")
                let node = SCNNode()
                let scene =  SCNScene(named:"mug.scn", inDirectory: ls)
                let nodess = scene?.rootNode.childNode(withName: "Mug", recursively: true)
                node.addChildNode(nodess!)
                let nodeArray = scene!.rootNode.childNodes
                for childNode in nodeArray {
                    node.addChildNode(childNode as SCNNode)
                }
                 self.addChildNode(node)
                 self.modelLoaded = true

        })
        downloadTask.resume()

的NSLog：

location:Optional(file:///private/var/mobile/Containers/Data/Application/A1B996D7-ABE9-4000-91DB-2370076198D5/tmp/CFNetworkDownload_duDlwf.tmp)

new location:/var/mobile/Containers/Data/Application/A1B996D7-ABE9-4000-91DB-2370076198D5/Documents/mug.scn

使用上述（新位置）文件路径下载.scn文件..但是当我尝试在SCNScene

中使用此下载文件时

let scene =  SCNScene(named:"mug.scn", inDirectory: ls)

始终场景值为nil。错误

线程4：致命错误：在展开可选值时意外发现nil

如何解决这个问题。谢谢

Answer 1

关于init?(named: String)，文档说：

从应用程序主包中具有指定名称的文件加载场景

由于您在主程序包中没有此类文件（来自下载），您可以尝试使用以下构造函数：

init(url: URL, options: [SCNSceneSource.LoadingOption : Any]? = nil)

所以你的代码可能是：

do {
   let documents = "yourValidPath"
   let scene = try SCNScene(url: URL(fileURLWithPath: documents), options: nil)
} catch {}

Answer 2

    let documentDirectory = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
    let pathToObject = documentDirectory + "ship.scn"
    let fileUrl = URL(fileURLWithPath: pathToObject)

    guard let cshipScene = try? SCNScene(url: fileUrl, options: nil) else { return }
    let shipNode = SCNNode()
    let shipSceneChildNodes = shipScene.rootNode.childNodes
    for childNode in shipSceneChildNodes {
        shipNode.addChildNode(childNode)
    }

    node.addChildNode(shipNode)

ARkit - 从SCNScene中的Web服务器URL加载.scn文件

2 个答案: