Unity实现已知落点和速度自动计算发射角度

/// <summary>
/// 挂载到发射器上即可
/// </summary>
public class rotate : monobehaviour
{
 public gameobject prefab; //发射物
 public float speed;   //发射物速度
 public bool 抛射 = false; //抛射：仰角 > 45°，否：仰角 < 45°
 ray raymouse;
 vector3 direction;
 quaternion rotation;
 
 void update()
 {
  if (input.getmousebuttondown(0))
  {
   gameobject go = instantiate(prefab, transform.position, transform.rotation);
   go.addcomponent<rigidbody>().velocity = go.transform.forward * speed;
  }

  raycasthit hit;
  raymouse = camera.main.screenpointtoray(input.mouseposition);
  if (physics.raycast(raymouse.origin, raymouse.direction, out hit, mathf.infinity))
  {
   rotatetomousedirection(gameobject, hit.point);
  }
 }

 /// <summary>
 /// 执行整体旋转
 /// </summary>
 /// <param name="obj">旋转的物体（自身）</param>
 /// <param name="destination">目标点（鼠标指向）</param>
 void rotatetomousedirection(gameobject obj, vector3 destination)
 {
  direction = destination - obj.transform.position;
  rotation = quaternion.lookrotation(direction);

  vector3 finalangle = rotation.eulerangles;
  float targetang = angle(destination);
  finalangle = new vector3(-targetang, finalangle.y, finalangle.z);//注意正负

  obj.transform.localrotation = quaternion.euler(finalangle);
 }

 /// <summary>
 /// 自动计算x欧拉角，即仰角
 /// </summary>
 /// <param name="target">目标点坐标</param>
 /// <returns></returns>
 float angle(vector3 target)
 {
  float anglex;
  float distx = vector2.distance(new vector2(target.x, target.z), new vector2(transform.position.x, transform.position.z));
  float disty = target.y - transform.position.y;
  float posbase = (physics.gravity.y * mathf.pow(distx, 2.0f)) / (2.0f * mathf.pow(speed, 2.0f));
  float posx = distx / posbase;
  float posy = (mathf.pow(posx, 2.0f) / 4.0f) - ((posbase - disty) / posbase);
  if (posy >= 0.0f)
  {
   if (抛射) //字段
    anglex = mathf.rad2deg * mathf.atan(-posx / 2.0f + mathf.pow(posy, 0.5f));
   else
    anglex = mathf.rad2deg * mathf.atan(-posx / 2.0f - mathf.pow(posy, 0.5f));
  }
  else
  {
   anglex = 45.0f;
  }
  return anglex;
 }
}