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

public class ItemScript4 : MonoBehaviour
{
    /// <summary>
    /// 要躲避的物體
    /// </summary>
    public Transform center;

    /// <summary>
    /// 引力位置
    /// </summary>
    public Vector3 gravitationPos = Vector3.zero;
    
 
/// <summary>
    /// 出生位置
    /// </summary>
    public Vector3 createPos = Vector3.zero;

    /// <summary>
    /// 力場影響範圍，半徑
    /// </summary>
    public float forceRadius = 4;
    /// <summary>
    /// 斥力
    /// </summary>
    public float repulsion;
    /// <summary>
    /// 吸引力
    /// </summary>
 

    public float targetAttractive;
    // Start is called before the first frame update
    void Start()
    {
        createPos= this.transform.position;
        gravitationPos= this.transform.position;
    }

    // Update is called once per frame
    void Update()
    {
        //速度
        var velocity = Vector3.zero;
        
 
//計算跟隨物體與力場物體的距離
        var len = (this.transform.position - center.position).magnitude;  //計算距離
        //如果距離小於範圍，就是處於力場之中
        if (len < forceRadius)
        {
            //力場半徑-距離/力場半徑
            var rate = (forceRadius - len) / forceRadius;
            //根據距離來計算力的強度（如果沒有這一步，會出現抖動）
            var intensity = repulsion * rate;
            //速度要加上這個值
            velocity += (this.transform.position - center.position) * intensity * Time.deltaTime;  //計算斥力
        }
        
        velocity += (gravitationPos - this.transform.position) * Time.deltaTime * targetAttractive;  //同時計算目標點的引力

        this.transform.position += velocity;

        //計算大小，跟隨物體與引力中心離的越近越小
        this.transform.localScale = Mathf.Clamp01((this.transform.position - center.position).magnitude / forceRadius) * Vector3.one;
    }
}