unity C# 计算3D空间任意多边形面积,距离,角度测量工具

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效果图

代码：

using UnityEngine;
using System.Collections.Generic;
using System;
/// <summary>
/// 划线面积,距离,角度
/// </summary>
public class UnderlinedMeasureTool : MonoBehaviour
{
    /// <summary>
    /// 相机
    /// </summary>
    public Camera _camera;
    public int size = 30;//文字大小
    //圆点的预制体
    public GameObject aim;
    public LineRenderer lineRender;
    bool sb = false;

    //GL 绘制的顶点数组  顺序是  0->1  2->3 4->5    取法 0 1 3 5 7 9
    //参考UI界面
    private List<Vector3> lv;//划线的点
    private List<Vector3> lv1;//存坐标的点
    public List<GameObject> aims;
    public int type = 3;
    void Start()
    {
        lv = new List<Vector3>();
        lv1 = new List<Vector3>();
        aims = new List<GameObject>();
    }
    void Update()
    {
        if (Input.GetMouseButtonDown(0))//绘制多边形
        {
            Ray ray = _camera.ScreenPointToRay(Input.mousePosition);
            RaycastHit hit;
            if (Physics.Raycast(ray, out hit, Mathf.Infinity))
            {
                //创建圆点
                GameObject go = Instantiate(aim, new Vector3(hit.point.x, hit.point.y, hit.point.z), Quaternion.Euler(90, 0, 0)) as GameObject;
                aims.Add(go);
                lv1.Add(hit.point);
                if (type == 1)
                {
                    if (lv.Count >= 2)
                    {
                        ClearLines();
                        GameObject go1 = Instantiate(aim, new Vector3(hit.point.x, hit.point.y, hit.point.z), Quaternion.Euler(90, 0, 0)) as GameObject;
                        aims.Add(go1);
                        lv1.Add(hit.point);

                        lv.Add(hit.point);
                    }
                    else
                    {
                        lv.Add(hit.point);
                    }
                }
                else if (type == 2)
                {
                    if (lv.Count >= 3)
                    {
                        ClearLines();
                        GameObject go1 = Instantiate(aim, new Vector3(hit.point.x, hit.point.y, hit.point.z), Quaternion.Euler(90, 0, 0)) as GameObject;
                        aims.Add(go1);
                        lv1.Add(hit.point);

                        lv.Add(hit.point);
                    }
                    else if (lv.Count >= 2)
                    {
                        if (sb)
                        {
                            lv.RemoveAt(lv.Count - 1);
                            lv.RemoveAt(lv.Count - 1);
                        }
                        lv.Add(hit.point);

                        sb = true;
                    }
                    else
                    {
                        lv.Add(hit.point);
                    }
                }
                else if (type == 3)
                {
                    if (lv.Count >= 2)
                    {
                        //存入点就是反复存入来自动连线，0--1 1--2 2--3.。。。。类似这格式存储点
                        if (sb)
                        {
                            lv.RemoveAt(lv.Count - 1);
                            lv.RemoveAt(lv.Count - 1);
                        }
                        lv.Add(lv[lv.Count - 1]);
                        lv.Add(hit.point);
                        lv.Add(lv[0]);
                        lv.Add(hit.point);

                        sb = true;
                    }
                    else
                    {
                        lv.Add(hit.point);
                    }
                }
               
            }
            //print(lv.Count);

            lineRender.positionCount = lv.Count;
            lineRender.SetPositions(lv.ToArray());
        }
    }

    void OnGUI()
    {
        GUIStyle text = new GUIStyle();
        text.fontSize = size;
        // 利用gui 为了实时动态更新画线数据
        if (lv.Count >= 2)
        {
            //除了第一个点和最后个点，其它点都是存了两遍
            for (int i = 0; i < lv.Count - 1; i = i + 2)
            {
                Vector3 s = new Vector3((lv[i].x + lv[i + 1].x) / 2, (lv[i].y + lv[i + 1].y) / 2, (lv[i].z + lv[i + 1].z) / 2);
                Vector3 a = _camera.WorldToScreenPoint(s);
                //注意屏幕坐标系与GUI的ui坐标系y轴相反,ToString(".000")保留小数点后3位数，几个零几位数
                //显示线段的长度
                GUI.Label(new Rect(a.x- size, Screen.height - a.y, 50, 20), "<color=red>" + Vector3.Distance(lv[i], lv[i + 1]).ToString(".000") + "</color>" + "<color=blue>" + "m" + "</color>",text);

            }
        }
        //显示面积
        if (lv1.Count > 2 && type == 3)
        {
            Vector3 a = _camera.WorldToScreenPoint(lv1[0]);
            GUI.Label(new Rect(a.x - 0, Screen.height - a.y, 50, 20), "<color=yellow>" + Compute_3D_polygon_area(lv1).ToString(".00") + "</color>" + "<color=blue>" + "㎡" + "</color>", text);
        }
        //显示角度
        if (lv1.Count == 3 && type == 2)
        {
            Vector3 a = _camera.WorldToScreenPoint(lv1[1]);
            GUI.Label(new Rect(a.x, Screen.height - a.y, 50, 20), "<color=yellow>" + Angle(lv1[1], lv1[0], lv1[lv1.Count - 1]).ToString(".000") + "</color>" + "<color=blue>" + "℃" + "</color>", text);
        }
    }
    // 清除重新测量
    public void ClearLines()
    {
        if (lv == null) return;
        sb = false;
        for (int i = 0; i < aims.Count; i++)
        {
            Destroy(aims[i]);
        }
        lv.Clear();
        lv1.Clear();
        aims.Clear();
        lineRender.positionCount = 0;
    }
    //计算任意多边形的面积，顶点按照顺时针或者逆时针方向排列，不需要考虑y轴的坐标. 2D
    public double ComputePolygonArea(List<Vector3> points)
    {
        int point_num = points.Count;
        if (point_num < 3) return 0.0;
        float s = points[0].y * (points[point_num - 1].x - points[1].x);
        for (int i = 1; i < point_num; ++i)
            s += points[i].y * (points[i - 1].x - points[(i + 1) % point_num].x);
        return Mathf.Abs(s / 2.0f);
    }
    public double Compute_3D_polygon_area(List<Vector3> points)
    {
        //points为任意多边形的点集合 注意输入时要按环的流动输入，不能乱序输入
        //此方法是3D空间的，相较于2D更具有普适性
        if (points.Count < 3) return 0.0;

        var P1X = points[0][0];
        var P1Y = points[0][1];
        var P1Z = points[0][2];
        var P2X = points[1][0];
        var P2Y = points[1][1];
        var P2Z = points[1][2];
        var P3X = points[2][0];
        var P3Y = points[2][1];
        var P3Z = points[2][2];

        var a = Mathf.Pow(((P2Y - P1Y) * (P3Z - P1Z) - (P3Y - P1Y) * (P2Z - P1Z)), 2) + Mathf.Pow(((P3X - P1X) * (P2Z - P1Z) - (P2X - P1X) * (P3Z - P1Z)), 2) + Mathf.Pow(((P2X - P1X) * (P3Y - P1Y) - (P3X - P1X) * (P2Y - P1Y)), 2);
        var cosnx = ((P2Y - P1Y) * (P3Z - P1Z) - (P3Y - P1Y) * (P2Z - P1Z)) / (Mathf.Pow(a, 0.5f));
        var cosny = ((P3X - P1X) * (P2Z - P1Z) - (P2X - P1X) * (P3Z - P1Z)) / (Mathf.Pow(a, 0.5f));
        var cosnz = ((P2X - P1X) * (P3Y - P1Y) - (P3X - P1X) * (P2Y - P1Y)) / (Mathf.Pow(a, 0.5f));

        var s = cosnz * ((points[points.Count - 1][0]) * (P1Y) - (P1X) * (points[points.Count - 1][1])) + cosnx * ((points[points.Count - 1][1]) * (P1Z) - (P1Y) * (points[points.Count - 1][2])) + cosny * ((points[points.Count - 1][2]) * (P1X) - (P1Z) * (points[points.Count - 1][0]));

        for (int i = 0; i < points.Count-1; i++)
        {
            var p1 = points[i];
            var p2 = points[i + 1];
            var ss = cosnz * ((p1[0]) * (p2[1]) - (p2[0]) * (p1[1])) + cosnx * ((p1[1]) * (p2[2]) - (p2[1]) * (p1[2])) + cosny * ((p1[2]) * (p2[0]) - (p2[2]) * (p1[0]));
            s += ss;
        }

        return Mathf.Abs(s / 2.0f);
    }
    //计算夹角
    public double Angle(Vector3 cen, Vector3 first, Vector3 second)
    {
        double M_PI = 3.1415926535897931;

        double ma_x = first.x - cen.x;
        double ma_y = first.y - cen.y;
        double ma_z = first.z - cen.z;
        double mb_x = second.x - cen.x;
        double mb_y = second.y - cen.y;
        double mb_z = second.z - cen.z;
        double v1 = (ma_x * mb_x) + (ma_y * mb_y) + (ma_z * mb_z);
        double ma_val = Math.Sqrt(ma_x * ma_x + ma_y * ma_y + ma_z * ma_z);
        double mb_val = Math.Sqrt(mb_x * mb_x + mb_y * mb_y + mb_z * mb_z);
        double cosM = v1 / (ma_val * mb_val);
        double angleAMB = Math.Acos(cosM) * 180 / M_PI;
        return angleAMB;
    }
}

原文链接：https://blog.csdn.net/qq_22972867/article/details/120452678

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