ARkit - 从SCNScene中的Web服务器URL加载.scn文件

Question

我正在为我的应用程序使用ARKit,我尝试从我的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()

NSLog的:

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

.scn文件下载与上面提到的(新位置)文件路径..但​​当我尝试使用此下载的文件 SCNScene

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

总是场景值是nil.错误

线程4:致命错误:在解开Optional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

由于你在主包中没有这样的文件(来自下载),你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 {}