public static Path GetParticlePath(Point start, Point end, byte[] rgb, Storyboard sb, PathGeometry geometry, double l)
        {
            Path path = new Path
            {
                Style       = (Style)Application.Current.Resources["ParticlePathStyle"],
                Data        = geometry,
                Stroke      = new System.Windows.Media.SolidColorBrush(System.Windows.Media.Color.FromArgb(255, rgb[0], rgb[1], rgb[2])),
                OpacityMask = StoryBoard.GetGradientBrush(start, end),
            };

            //path.ToolTip = string.Format("{0}=>{1}",mapitem.ToString(), toItem.To.ToString());

            var particleTime = 1 / l;

            DoubleAnimation pda0 = StoryBoard.Animation3(particleTime);


            //Path particlePath = PathEllipse.GetParticlePath(startPoint, endPoint, rgb, m_angle, out double l);
            //particlePath.

            Storyboard.SetTarget(pda0, path);
            Storyboard.SetTargetProperty(pda0, new PropertyPath("(Path.OpacityMask).(GradientBrush.GradientStops)[0].(GradientStop.Offset)"));
            sb.Children.Add(pda0);



            var pda1 = StoryBoard.Animation3(particleTime);

            Storyboard.SetTarget(pda1, path);
            Storyboard.SetTargetProperty(pda1, new PropertyPath("(Path.OpacityMask).(GradientBrush.GradientStops)[1].(GradientStop.Offset)"));
            sb.Children.Add(pda1);


            return(path);
        }