ios - Could not open OBJ file when convert MDLAsset to MDLMesh

I'm working with demonstrating loading and texturing a .OBJ file using ModelIO. This code bellow works fine when I use local file.

guard let url = Bundle.main.url(forResource: "myVase", withExtension: "obj") else {
    fatalError("Failed to find model file.")
}

let asset = MDLAsset(url:url)
guard let object = asset.object(at: 0) as? MDLMesh else {
    fatalError("Failed to get mesh from asset.")
}

But, when I change my code to use file from my Amazon S3 instead of local file. I got errors: "Could not open OBJ file" & "Failed to get mesh from asset." Here is my code:

let url = URL.init(string: "https://s3.amazonaws.com/myObject/.../object.obj")

let asset = MDLAsset(url:url!)
guard let object = asset.object(at: 0) as? MDLMesh else {
   fatalError("Failed to get mesh from asset.")
}

Note: I made the link public and free to download.

1 answer

  • answered 2018-03-14 12:32 Khoa

    I fixed my issue. My issue is that I converted the file before the downloading is finished. Therefore, the local path is created but data is empty because download process hasn't finished yet.

    To solve it, I use async to finish downloading first then converting it.

    let destination: DownloadRequest.DownloadFileDestination = { _, _ in
       let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
       let fileURL = documentsURL.appendingPathComponent("myVase.obj")     
       return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
    }
    
    Alamofire.download(urlString, to: destination).response { response in
        if response.error == nil, let filePath = response.destinationURL?.path {
           print(imagePath)
           let myUrl = "file://" + filePath
    
           let asset = MDLAsset(url:URL(string:myUrl)!)
           guard let object = asset.object(at: 0) as? MDLMesh else {
               fatalError("Failed to get mesh from asset.")
           }
            ...
        }
    }