trajectory

代码说明：

  产生轨迹，可以产生直线轨迹，直线加速轨迹，转弯轨迹，得到的物体真实运动的轨迹，并且显示出来。(Have a track, you can have a straight-line trajectory, a straight-line speed up the track, turning the track has been real movement of the object trajectory, and displayed.)