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

public class BezierUtils
{
    /// <summary> 
    /// 二次贝塞尔曲线：根据T值，计算贝塞尔曲线上面相对应的点
    /// </summary> 
    /// <param name="t"></param>T值 
    /// <param name="pStartV"></param>起始点 
    /// <param name="pControlV"></param>控制点 
    /// <param name="pEndV"></param>目标点 
    /// <returns></returns>根据T值计算出来的贝赛尔曲线点 
    public static Vector3 CalculateBezierPointN2(float t, Vector3 pStartV, Vector3 pControlV, Vector3 pEndV)
    {
        float u = 1 - t;

        Vector3 tPos = u * u * pStartV;
        tPos += 2 * u * t * pControlV;
        tPos += t * t * pEndV;

        return tPos;
    }

    /// <summary> 
    /// 二次贝塞尔曲线：获取存储贝塞尔曲线点的数组
    /// </summary> 
    /// <param name="pStartV"></param>起始点 
    /// <param name="pControlV"></param>控制点 
    /// <param name="pEndV"></param>目标点 
    /// <param name="pSegment"></param>采样点的数量 
    /// <returns></returns>存储贝塞尔曲线点的数组 
    public static Vector3[] GetBezierListN2(Vector3 pStartV, Vector3 pControlV, Vector3 pEndV, int pSegment)
    {
        Vector3[] tPath = new Vector3[pSegment + 1];
        for (int i = 0; i <= pSegment; i++)
        {
            float t = i / (float)pSegment;
            Vector3 pixel = CalculateBezierPointN2(t, pStartV, pControlV, pEndV);
            tPath[i] = pixel;
        }
        return tPath;
    }

    /// <summary>
    /// 二次贝塞尔曲线：根据T值，计算贝塞尔曲线上面相对应的点
    /// </summary>
    /// <param name="t"></param>T值
    /// <param name="pStartV"></param>起始点
    /// <param name="pControlV1"></param>控制点1
    /// <param name="pControlV2"></param>控制点2
    /// <param name="pEndV"></param>目标点
    /// <returns></returns>根据T值计算出来的贝赛尔曲线点
    public static Vector3 CalculateBezierPointN3(float t, Vector3 pStartV, Vector3 pControlV1, Vector3 pControlV2, Vector3 pEndV)
    {
        float u = 1 - t;

        Vector3 tPos = Vector3.zero;
        tPos = u * u * u * pStartV;
        tPos += 3 * u * u * t * pControlV1;
        tPos += 3 * u * t * t * pControlV2;
        tPos += t * t * t * pEndV;

        return tPos;
    }

    /// <summary>
    /// 三次贝塞尔曲线：获取存储贝塞尔曲线点的数组
    /// </summary>
    /// <param name="pStartV"></param>起始点
    /// <param name="pControlV1"></param>控制点1
    /// <param name="pControlV2"></param>控制点2
    /// <param name="pEndV"></param>目标点
    /// <param name="pSegment"></param>采样点的数量
    /// <returns></returns>存储贝塞尔曲线点的数组
    public static Vector3[] GetBezierListN3(Vector3 pStartV, Vector3 pControlV1, Vector3 pControlV2, Vector3 pEndV, int pSegment)
    {
        Vector3[] tPath = new Vector3[pSegment + 1];
        for (int i = 0; i <= pSegment; i++)
        {
            float t = i / (float)pSegment;
            Vector3 pixel = CalculateBezierPointN3(t, pStartV, pControlV1, pControlV2, pEndV);
            tPath[i] = pixel;
        }
        return tPath;
    }
}