unity 实现摄像机绕某点旋转一周

if (turnaround)
  {
    playercamera.rotatearound(transform.localposition, transform.up, time.deltatime * rotatespeed);
    degree += time.deltatime * rotatespeed;
    if (degree >= 360)
    {
      turnaround = false;        
      degree = 0;
     }
   }

public transform camera2;
public gameobject target;
private float dis;
public float xspeed = 200, yspeed = 200, mspeed = 10;                   //移动速度
public float yminlimit = -50, ymaxlimit = 50;                           //摄像机的y轴移动最小最大限制
public float distance = 7, mindistance = 2, maxdistance = 30;           //摄像机与目标物体的距离
public bool needdamping = true;                                         //阻尼默认开启
float damping = 5.0f;                                                   //默认阻尼为5.0f
public float x = 0.0f;                                                  //x轴
public float y = 0.0f;                                                  //y轴
// use this for initialization
void start() {
    instance = this;
    camr = camera2rotation.close;
    vector3 angles = transform.eulerangles;
    x = angles.y;
    y = angles.x;  
}
private void update()
{
}
void lateupdate()
{
            //使用按下鼠标左键移动物体
            if (input.getmousebutton(1))
            {
                x += input.getaxis("mouse x") * xspeed * 0.02f;
                y -= input.getaxis("mouse y") * yspeed * 0.02f;
                y = clampangle(y, yminlimit, ymaxlimit);
            }
            distance -= input.getaxis("mouse scrollwheel") * mspeed;
            distance = mathf.clamp(distance, mindistance, maxdistance);
            quaternion rotation = quaternion.euler(y, x, 0.0f);
            vector3 disvector = new vector3(0.0f, 0.0f, -distance);
            vector3 position = rotation * disvector + target.transform.position;
            //adjust the camera
            if (needdamping)
            {
                transform.rotation = quaternion.lerp(transform.rotation, rotation, time.deltatime * damping);
                transform.position = vector3.lerp(transform.position, position, time.deltatime * damping);
            }
            else
            {
                transform.rotation = rotation;
                transform.position = position;
            }   
}
/// <summary>
/// 旋转角度的控制
/// </summary>
/// <param name="angle">旋转的角度</param>
/// <param name="min">最小角度</param>
/// <param name="max">最大角度</param>
/// <returns></returns>
static float clampangle(float angle, float min, float max)
{
    if (angle < -360)
        angle += 360;
    if (angle > 360)
        angle -= 360;
    return mathf.clamp(angle, min, max);
}
void movecameratotarget()
{
    if (target != null)
    {
        camera2.lookat(target.transform);
        camera2.position = vector3.movetowards(camera2.position, target.transform.position, 5 * time.deltatime);
        dis = vector3.distance(camera2.transform.position, target.transform.position);
        if (dis < 1.5f)
        {
            camr = camera2rotation.open;
            cancelinvoke();
        }
    }
}