image.png

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

public class MyLine : MaskableGraphic
{
    public Color[] LineColor = new Color[] { new Color(0, 1, 0, 0.5f), Color.red, Color.blue };

    public Vector3 p1;
    public Vector3 p2;

    public Vector3[] points;
    public float LineWidth = 1;

    protected override void OnPopulateMesh(VertexHelper vh)
    {
        vh.Clear();

        if (points.Length < 2)
        {
            return;
        }
        //獲取繞Z軸旋轉(zhuǎn)90度的矩陣 這樣就可以得到垂直于這條線段的點 就能根據(jù)寬度繪制mesh點
        var mr = GetMatrixRotateZ(90);
        var ml = GetMatrixRotateZ(-90);

        for (int i = 0; i < points.Length - 1; i++)
        {
            Vector3 p0r = RotatePoint(points[i], points[i + 1], mr);
            Vector3 p0l = RotatePoint(points[i], points[i + 1], ml);
            Vector3 p1r = RotatePoint(points[i + 1], points[i], mr);
            Vector3 p1l = RotatePoint(points[i + 1], points[i], ml);

            //添加點
            vh.AddVert(p0r, LineColor[0], Vector2.zero);
            vh.AddVert(p0l, LineColor[0], Vector2.zero);
            vh.AddVert(p1r, LineColor[1], Vector2.zero);
            vh.AddVert(p1l, LineColor[1], Vector2.zero);

            int baseIndex = i * 4;
            //添加面
            vh.AddTriangle(baseIndex + 0, baseIndex + 2, baseIndex + 1);
            vh.AddTriangle(baseIndex + 0, baseIndex + 3, baseIndex + 2);
        }


        //下面注釋是只有兩個點 不使用循環(huán)寫法

        //Vector3 pp1 = mr * (p1 - p2).normalized;
        //Vector3 pp2 = ml * (p1 - p2).normalized;
        //Vector3 pp3 = mr * (p2 - p1).normalized;
        //Vector3 pp4 = ml * (p2 - p1).normalized;

        //pp1 *= LineWidth;
        //pp2 *= LineWidth;
        //pp3 *= LineWidth;
        //pp4 *= LineWidth;

        //pp1 += p1;
        //pp2 += p1;
        //pp3 += p2;
        //pp4 += p2;

        //vh.AddVert(pp1, c[0], Vector2.zero);
        //vh.AddVert(pp2, c[0], Vector2.zero);
        //vh.AddVert(pp3, c[1], Vector2.zero);
        //vh.AddVert(pp4, c[1], Vector2.zero);

        //vh.AddTriangle(0, 2, 1);
        //vh.AddTriangle(0, 3, 2);

    }


    public Vector3 RotatePoint(Vector3 p1, Vector3 p2, Matrix4x4 m)
    {
        //p1 - p2 得到兩點連線指向p1的向量 標準化后長度為1 左乘矩陣后得到垂直向量
        Vector3 pp1 = m * (p1 - p2).normalized;
        //由于原向量標準化了 所以旋轉(zhuǎn)后的向量長度還是1 所以直接乘上寬度
        pp1 *= LineWidth;
        //向量相加 得到點的坐標(Vector3 既可以是坐標 也可以是方向 注意區(qū)分算出來的結(jié)果是坐標還是方向)
        pp1 += p1;
        return pp1;
    }

    //構(gòu)造一個 旋轉(zhuǎn)矩陣
    public Matrix4x4 GetMatrixRotateZ(float angle = 90)
    {
        angle = angle * Mathf.Deg2Rad;

        var rotateZMatrix = Matrix4x4.identity;

        rotateZMatrix.m00 = Mathf.Cos(angle);
        rotateZMatrix.m01 = Mathf.Sin(angle);

        rotateZMatrix.m10 = -Mathf.Sin(angle);
        rotateZMatrix.m11 = Mathf.Cos(angle);
        return rotateZMatrix;
    }
}