Unity 2D游戏中的抛物运动

using UnityEngine;

public class ProjectileMotion : MonoBehaviour
{
    //投掷物
    [SerializeField] private GameObject bomb;
    //力
    [SerializeField] private float force;

    [SerializeField] LineRenderer lineRenderer;

    private float theta;
    //速度
    private float velocity;

    Vector3[] ves;

    private void Start()
    {
        lineRenderer.positionCount = 100;
        ves = new Vector3[100];
    }
    Vector2 dir;
    private void Update()
    {
        //弧度
        float yLength = Camera.main.ScreenToWorldPoint(Input.mousePosition).y - transform.position.y;
        float xLength = Camera.main.ScreenToWorldPoint(Input.mousePosition).x - transform.position.x;
        //返回其切线为两个浮点数的商的角度。
        theta = Mathf.Atan2(yLength, xLength);
        dir = ((Vector2)Camera.main.ScreenToWorldPoint(Input.mousePosition) - (Vector2)transform.position).normalized;
        //速度
        velocity = (dir * force).magnitude;

        if (Input.GetKeyDown(KeyCode.J))
        {
            GameObject Projectile = Instantiate<GameObject>(bomb, transform.position, Quaternion.identity);
            Projectile.GetComponent<Rigidbody2D>().velocity = dir * force;
        }
      
        for (int i = 0; i < 100; i++)
        {
            float t = i * 0.05f;
            float x = velocity * t * Mathf.Cos(theta) + transform.position.x;
            float y = velocity * t * Mathf.Sin(theta) + 0.5f * Physics2D.gravity.y * t * t + transform.position.y;
            ves[i] = new Vector3(x, y, 0);
        }

        lineRenderer.SetPositions(ves);
    }
}