r=Math.Pi/6;
butterfly_sprite[0].SetX(Window.GetWidth() / 2 + Math.Cos(theta) * a * Math.Cos(r) + Math.Sin(theta) * b * Math.Sin(r));
butterfly_sprite[0].SetY(Window.GetHeight() / 2 - Math.Cos(theta) * a * Math.Sin(r) + Math.Sin(theta) * b * Math.Cos(r));
butterfly_sprite[0].SetImage(butterfly_images[Math.Int(progress / 6) % 4].Rotate(theta));
r=0-Math.Pi/2;
butterfly_sprite[1].SetX(Window.GetWidth() / 2 + Math.Cos(theta) * a * Math.Cos(r) + Math.Sin(theta) * b * Math.Sin(r));
butterfly_sprite[1].SetY(Window.GetHeight() / 2 - Math.Cos(theta) * a * Math.Sin(r) + Math.Sin(theta) * b * Math.Cos(r));
butterfly_sprite[1].SetImage(butterfly_images[Math.Int(progress / 6) % 4].Rotate(theta));
r=Math.Pi/6*5;
butterfly_sprite[2].SetX(Window.GetWidth() / 2 + Math.Cos(theta) * a * Math.Cos(r) + Math.Sin(theta) * b * Math.Sin(r));
butterfly_sprite[2].SetY(Window.GetHeight() / 2 - Math.Cos(theta) * a * Math.Sin(r) + Math.Sin(theta) * b * Math.Cos(r));
butterfly_sprite[2].SetImage(butterfly_images[Math.Int(progress / 6) % 4].Rotate(theta));
三个椭圆运动起来后完全看不出是三个椭圆轨迹组成的:4_95:快速运动后,残影还会形成一个三角形:4_98: