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

using UnityEngine;

public class draw_parabola : MonoBehaviour
{
    public Transform startTrans;
    public Transform endTrans;
    public LineRenderer lineRender;
    Vector3[] path;
    void Start()
    {
        draw_parabola_true(startTrans.position, endTrans.position, 10, 5);
    }
    /// <summary>
    /// 绘制抛物线
    /// </summary>
    /// <param name="startPoint">初始点</param>
    /// <param name="endPoint">结束点</param>
    /// <param name="resolution">路径点数量</param>
    void draw_parabola_true(Vector3 startPoint, Vector3 endPoint, int resolution, float height)
    {
        var bezierControlPoint = (startPoint + endPoint) * 0.5f + (Vector3.up * height);
        path = new Vector3[resolution];//resolution为int类型，表示要取得路径点数量，值越大，取得的路径点越多，曲线最后越平滑
        for (int i = 0; i < resolution; i++)
        {
            var t = (i + 1) / (float)resolution;//归化到0~1范围
            path[i] = GetBezierPoint(t, startPoint, bezierControlPoint, endPoint);//使用贝塞尔曲线的公式取得t时的路径点
        }
        lineRender.positionCount = path.Length;
        lineRender.SetPositions(path);
    }

    /// <param name="t">0到1的值，0获取曲线的起点，1获得曲线的终点</param>
    /// <param name="start">曲线的起始位置</param>
    /// <param name="center">决定曲线形状的控制点</param>
    /// <param name="end">曲线的终点</param>
    public static Vector3 GetBezierPoint(float t, Vector3 start, Vector3 center, Vector3 end)
    {
        return (1 - t) * (1 - t) * start + 2 * t * (1 - t) * center + t * t * end;
    }
}