ARKit - 如何从服务器URL下载3d模型？

Question

我正在尝试从URl下载3d模型并放入ARKit应用程序。这是我的代码：

func addItem(hitTestResult: ARHitTestResult) {
    let url = URL(string: "https://doc-0k-9s-docs.googleusercontent.com/docs/securesc/hbcaqfp5mt16eq0ub4t5v9ch588idcc9/66jirrfaadh438gudijui5vq39hblj21/1519236000000/11854387276548053415/11854387276548053415/1ab55L4__Qy7HSPf10-a4H3lqUdWSvPLl?e=download")
    if let objectScene = try? SCNScene(url: url!, options: [.overrideAssetURLs: true]) {
        print("load successful")
        let node = SCNNode()
        for childNode in objectScene.rootNode.childNodes {
            node.addChildNode(childNode)
        }
        sceneView.scene.rootNode.addChildNode(node)
    } else {
        print("Error loading")
    }
}

它在objectScene行崩溃了。如何解决这个问题。谢谢