Add possibility to use AssetBundle from a given url for mesh tracking

Unity serializes .arobject into ARKitReferenceObjectEntry in the editor. ARKitReferenceObjectEntry cannot then be imported at runtime from a .arobjject file. Dynamic loading is not supported yet.

To support adding .arobject without recompiling the full application, we use a dedicated AssetBundle (named "arfmeshes"). To do so:

To support adding .arobject without recompiling the full application, we use a dedicated AssetBundle.

* Place you .arobject in the Assets Folder. For instance under Assets/ARObjects

* Associate the ARKitReferenceObjectEntry with the arfmeshes AssetBundle in the editor

* Build the AssetBundles. For that you can use the following menu: ARF--> Build AssetBundles iOS

* Pace the "arfmeshes" file in the Unity persistent data path of the application on the user device.

Then you have two options:

* Placing the AssetBundle "arfmeshes" file (with this exact file name) in the Unity persistent data path of the application on the user device.

* The variable keyvalueTags of the Trackable can also contain a parameter with the "url" key providing a link to download the AssetBundle to the Unity persistent data path on the user device. Only one AssetBundle can be loaded.

The name of the Trackable in the World Storage must correspond to the name of the ARKitReferenceObjectEntry.

    /// </summary>

    private List<string> m_trackedMeshesInLibrary;

    /// <summary>

    /// Has downloaded asset bundle from an url

    /// </summary>

    private bool m_hasDownloadedBundle; 

    /// <summary>

    /// List of tracked meshses with tracking infos

    /// </summary>

    private Dictionary<string,TrackableInfo> m_trackedMeshes = new Dictionary<string,TrackableInfo>();

        m_trackedObjectManager.trackedObjectsChanged += OnTrackedMeshesChanged;

        m_trackedObjectManager.enabled = true ; // when instantiated without library : it is disabled

        m_entries = null;

        #if UNITY_EDITOR

            string bundlePath = Application.streamingAssetsPath + "/arfmeshes" ;

        #else

            string bundlePath = Application.persistentDataPath  + "/arfmeshes" ;

        #endif

        if (System.IO.File.Exists(bundlePath))

        {

            AssetBundle bu = AssetBundle.LoadFromFile(bundlePath);

            m_entries = bu.LoadAllAssets<XRReferenceObjectEntry>() ;

        }

        m_hasDownloadedBundle = false; 

    }

    /// <summary>

        {

            return false;

        }

        bool resul = AddMeshToLibrary(trackable.Name) ;// (float)trackable.TrackableSize[0]);

        // Check if an AssetBundle url is provided

        string url = "";

        if (trackable.KeyvalueTags.ContainsKey("url"))

        {

            foreach (string s in trackable.KeyvalueTags["url"])

            {

                // first one

                url = s;

                break;

            }

        }

        bool resul = AddMeshToLibrary(trackable.Name , url) ;// (float)trackable.TrackableSize[0]);

        if (resul)

        {

            m_uuidToName[trackable.UUID] = trackable.Name;

    }

    /// <summary>

    ///  Initialize capability object with image tracking

    ///  Initialize capability object with Mesh tracking

    /// </summary>

    public ETSI.ARF.OpenAPI.WorldAnalysis.Capability  GetSupportedCapability()

    {

    /// </summary>

    /// <param name="fileName">file name</param>

    /// <returns></returns>

    protected bool AddMeshToLibrary(string fileName)

    protected bool AddMeshToLibrary(string fileName, string url)

    {

        // check if mesh is in the library

        if (m_trackedMeshesInLibrary.Contains(fileName))

        if (m_entries == null)

        {

            Debug.LogWarning("Try to Track Mesh but ARF Bundle with meshes is null");

#if UNITY_EDITOR

            string bundlePath = Application.streamingAssetsPath + "/arfmeshes";

#else

            string bundlePath = Application.persistentDataPath  + "/arfmeshes" ;

#endif

            if (url.Length > 0 && !m_hasDownloadedBundle)

            {

                KeyValuePair<string, string> download = System.Threading.Tasks.Task.Run(() => WorldAnalysisARFoundationHelper.DownloadFileHTTP(url)).Result; // synchronous : not perfect at all prevent to add another mesh while bundle is downloading

                bundlePath = download.Key;

                m_hasDownloadedBundle = true;

            }

            if (System.IO.File.Exists(bundlePath))

            {

                AssetBundle bu = AssetBundle.LoadFromFile(bundlePath);

                m_entries = bu.LoadAllAssets<XRReferenceObjectEntry>();

            }

            else

            {

                return false;

            }

        }

        XRReferenceObjectEntry toAdd = null ;

        foreach(XRReferenceObjectEntry entry in m_entries)