在发射物已知落点和速度的情况下如果刚体应用重力，不容易算出发射角度，以下为计算过程

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//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().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);  } } 

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/// 目标点（鼠标指向） 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); }

 ///

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; }}