Distortion on 3d ojbect in UrhoSharp

What I'm trying to do is implementing a 360 degree image viewer.
I'm using UrhoSharp and here are the steps of what I've done to view a 360 degree image:

• Creating a 3d sphere model
• Loading a 360 degree (Panorama) image
• Set image as the Material of the Sphere

All the above steps are OK and I can see the flatten image from different view points but the problem is some kind of waves or distortions are in the image and the line which supposed to be straight are wavy. I don't know what setting could solve the problem, please help.

Here is the wavy outcome:

And here is my code:

private void CreateScene()
{
        // Scene
        var scene = new Scene();
        scene.CreateComponent<Octree>();


        // Node (Rotation and Position)
        var node = scene.CreateChild("room");
        node.Position = new Vector3(0, 0, 0);
        //node.Rotation = new Quaternion(10, 60, 10);
        node.SetScale(1f);

        // Model
        var modelObject = node.CreateComponent<StaticModel>();
        modelObject.Model = ResourceCache.GetModel("Models/Sphere.mdl");

        var zoneNode = scene.CreateChild("Zone");
        var zone = zoneNode.CreateComponent<Zone>();
        zone.SetBoundingBox(new BoundingBox(-300.0f, 300.0f));
        zone.AmbientColor = new Color(1f, 1f, 1f);

        //get image from byte[]

        //var url = "http://www.wsj.com/public/resources/media/0524yosemite_1300R.jpg";
        //var wc = new WebClient() { Encoding = Encoding.UTF8 };

        //var mb = new MemoryBuffer(wc.DownloadData(new Uri(url)));
        var mb = new MemoryBuffer(PanoramaBuffer.PanoramaByteArray);
        var image = new Image(Context) { Name = "MyImage" };
        image.Load(mb);

        //or from resource

        //var image = ResourceCache.GetImage("Textures/grave.jpg");
        var isFliped = image.FlipHorizontal();
        if (!isFliped)
        {
            throw new Exception("Unsuccessful flip");
        }
        var m = Material.FromImage(image);
        m.SetTechnique(0, CoreAssets.Techniques.DiffNormal, 0, 0);
        m.CullMode = CullMode.Cw;
        //m.SetUVTransform(Vector2.Zero, 0, 0);
        modelObject.SetMaterial(m);

        // Camera
        var cameraNode = scene.CreateChild("camera");
        var camera = cameraNode.CreateComponent<Camera>();
        camera.Fov = 75.8f;

        // Viewport
        Renderer.SetViewport(0, new Viewport(scene, camera, null));
    }