unity 关于射箭时候抛物线,计算

记录一下，
 

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class BulletTest : MonoBehaviour
{
    private Vector2 target_pos;
    private Rigidbody2D _rigidbody;
    private float x_Speed=10;
    private float mass = -9.8f;
    private float y_speed;
    private float moveTime;

    private Vector3 MoveSpeed;
    private Vector3 MasSpeed = Vector2.zero;

    private bool ismove = false;
    public void Init(Transform monster)
    {
        target_pos = monster.position;
        float x = target_pos.x - transform.position.x;
        float y = -transform.position.y + target_pos.y;
        //计算箭只移动到目的地的时间
        moveTime = x / x_Speed;
        //计算y轴上的初始速度
        y_speed = y / moveTime - 0.5f*mass * moveTime;

        //初始速度向量
        MoveSpeed = new Vector3(x_Speed, y_speed);

        //旋转角度
        float eul = Mathf.Atan(y_speed / x_Speed) * 180 / Mathf.PI;
        this.