• 根据顶点列表生成三角形数组


    根据顶点列表生成三角形数组
    Triangulator.cs

    using UnityEngine;
    using System.Collections.Generic;
    
    public class Triangulator
    {
        private static List<Vector2> points;
        private static Vector3 cameraPosition;
    
        public static Vector2[] ToVector2(Vector3[] m_points)
        {
            Vector2[] vertices2d = new Vector2[m_points.Length];
            for (int i = 0; i < m_points.Length; i++)
            {
                Vector3 pos = m_points[i];
                vertices2d[i] = new Vector2(pos.x, pos.z);
            }
            return vertices2d;
        }
    
        public static int[] Triangulate(Vector2[] m_points, Vector3 m_cameraPosition)
        {
            points = new List<Vector2>(m_points);
            cameraPosition = m_cameraPosition;
    
            List<int> indices = new List<int>();
    
            int n = points.Count;
            if (n < 3)
                return indices.ToArray();
    
            int[] V = new int[n];
            if (Area() > 0)
            {
                for (int v = 0; v < n; v++)
                    V[v] = v;
            }
            else
            {
                for (int v = 0; v < n; v++)
                    V[v] = (n - 1) - v;
            }
    
            int nv = n;
            int count = 2 * nv;
            for (int m = 0, v = nv - 1; nv > 2;)
            {
                if ((count--) <= 0)
                    break;
    
                int u = v;
                if (nv <= u)
                    u = 0;
                v = u + 1;
                if (nv <= v)
                    v = 0;
                int w = v + 1;
                if (nv <= w)
                    w = 0;
    
                if (Snip(u, v, w, nv, V))
                {
                    int a, b, c, s, t;
                    a = V[u];
                    b = V[v];
                    c = V[w];
                    indices.Add(a);
                    indices.Add(b);
                    indices.Add(c);
                    m++;
                    for (s = v, t = v + 1; t < nv; s++, t++)
                        V[s] = V[t];
                    nv--;
                    count = 2 * nv;
                }
            }
    
            bool reversFlag = true;
            int i0 = indices[0];
            int i1 = indices[1];
            int i2 = indices[2];
            Vector3 pos0 = new Vector3(points[i0].x, 0f, points[i0].y);
            Vector3 pos1 = new Vector3(points[i1].x, 0f, points[i1].y);
            Vector3 pos2 = new Vector3(points[i2].x, 0f, points[i2].y);
            Vector3 v1 = pos1 - pos0;
            Vector3 v2 = pos2 - pos1;
            Vector3 crossVec = Vector3.Cross(v1, v2);
            if (Vector3.Dot(cameraPosition, crossVec) > 0)
            {
                reversFlag = false;
            }
            if (reversFlag)
            {
                indices.Reverse();
            }
    
            return indices.ToArray();
        }
    
        private static float Area()
        {
            int n = points.Count;
            float A = 0.0f;
            for (int p = n - 1, q = 0; q < n; p = q++)
            {
                Vector2 pval = points[p];
                Vector2 qval = points[q];
                A += pval.x * qval.y - qval.x * pval.y;
            }
            return (A * 0.5f);
        }
    
        private static bool Snip(int u, int v, int w, int n, int[] V)
        {
            int p;
            Vector2 A = points[V[u]];
            Vector2 B = points[V[v]];
            Vector2 C = points[V[w]];
            if (Mathf.Epsilon > (((B.x - A.x) * (C.y - A.y)) - ((B.y - A.y) * (C.x - A.x))))
                return false;
            for (p = 0; p < n; p++)
            {
                if ((p == u) || (p == v) || (p == w))
                    continue;
                Vector2 P = points[V[p]];
                if (InsideTriangle(A, B, C, P))
                    return false;
            }
            return true;
        }
    
        private static bool InsideTriangle(Vector2 A, Vector2 B, Vector2 C, Vector2 P)
        {
            float ax, ay, bx, by, cx, cy, apx, apy, bpx, bpy, cpx, cpy;
            float cCROSSap, bCROSScp, aCROSSbp;
    
            ax = C.x - B.x; ay = C.y - B.y;
            bx = A.x - C.x; by = A.y - C.y;
            cx = B.x - A.x; cy = B.y - A.y;
            apx = P.x - A.x; apy = P.y - A.y;
            bpx = P.x - B.x; bpy = P.y - B.y;
            cpx = P.x - C.x; cpy = P.y - C.y;
    
            aCROSSbp = ax * bpy - ay * bpx;
            cCROSSap = cx * apy - cy * apx;
            bCROSScp = bx * cpy - by * cpx;
    
            return ((aCROSSbp >= 0.0f) && (bCROSScp >= 0.0f) && (cCROSSap >= 0.0f));
        }
    }
    
     mesh.triangles = Triangulator.Triangulate(Triangulator.ToVector2(points), Camera.main.transform.position);
    
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  • 原文地址:https://www.cnblogs.com/kingBook/p/11417194.html
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