Silverlight balder建立简单位移动画时出现问题

初学Silverlight和balder，使用Silverlight4和balder 0.8.8.9建立项目， 试用coordinateAnimation创建一个方块位移的简单动画。

代码如下：

 namespace _3Dani
{
    public partial class MainPage : UserControl
    {
        Game game = null;
        Balder.Objects.Geometries.Box testB = null;



        public MainPage()
        {
            InitializeComponent();

            game = new Game() { Width = 1280, Height = 600 };
            game.Camera = new Camera();
            game.Camera.Position = new Coordinate(150, 100, 100);
            game.Camera.Target = new Coordinate(0, 0, 0);
            game.Children.Add(new OmniLight() { Position = new Coordinate(0, 0, 0) });

            testB = new Box();
            testB.Name = "container";
            testB.Dimension = new Coordinate(20, 80, 10);
            testB.Position = new Coordinate(0, 0, 0);
            testB.InteractionEnabled = true;
            //testB.PivotPoint = new Coordinate(10, 0, 5);
            testB.Color = Color.FromArgb(100, 150, 150, 150);

            game.Children.Add(testB);
            LayoutRoot.Children.Add(game);



        }

        private void play_Click(object sender, RoutedEventArgs e)
        {
            CoordinateAnimation ani = new CoordinateAnimation();
            ani.Duration = TimeSpan.FromMilliseconds(1000);
            ani.Target = testB;
            ani.TargetName = "container";
            ani.TargetProperty = "(Node.Position)";
            ani.From = new Coordinate(0, 0, 0);
            ani.To = new Coordinate(50, 0, 0);
            Storyboard sb = new Storyboard();
            StoryboardExtensions.SetCoordinateAnimation(sb, ani);
            sb.Begin();
        }
    }
}

XAML页面仅有一个名为layoutRoot的Grid和一个名为play的button。

执行调试，点击play按钮以后，方块testB并不移动，此时用鼠标去旋转方块testB，方块就会突然闪到动画结束的位置。

执行调试，若先用鼠标去旋转方块testB，则动画正常执行。但这就意味着testB的InteractionEnabled属性必须设置为true，而且每次动画前都要手动旋转物体，十分不方便。

所以求问一下，要怎样才能做到点击play按钮，方块testB能直接执行动画，而不用再去拖动方块。

谢谢各位。