120 lines
3.3 KiB
C#
120 lines
3.3 KiB
C#
using UnityEngine;
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using System.Collections.Generic;
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public class Triangulator
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{
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private List<Vector2> m_points = new List<Vector2>();
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public Triangulator(Vector2[] points)
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{
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m_points = new List<Vector2>(points);
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}
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public int[] Triangulate()
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{
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List<int> indices = new List<int>();
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int n = m_points.Count;
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if (n < 3)
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return indices.ToArray();
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int[] V = new int[n];
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if (Area() > 0)//如果逆时针选点，点的index正向记录
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{
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for (int v = 0; v < n; v++)
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V[v] = v;
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}
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else
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{//如果顺时针选点，点的index反向记录
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for (int v = 0; v < n; v++)
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V[v] = (n - 1) - v;
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}
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int nv = n;
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int count = 2 * nv;
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for (int v = nv - 1; nv > 2;)
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{
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if ((count--) <= 0)
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return indices.ToArray();
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int u = v;
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if (nv <= u)
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u = 0;
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v = u + 1;
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if (nv <= v)
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v = 0;
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int w = v + 1;
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if (nv <= w)
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w = 0;
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if (Snip(u, v, w, nv, V))//u,v,w三点是否能构成三角面
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{
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int a, b, c, s, t;
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a = V[u];
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b = V[v];
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c = V[w];
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indices.Add(a);
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indices.Add(b);
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indices.Add(c);
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for (s = v, t = v + 1; t < nv; s++, t++)//增加一个三角数据，把这个三角剪去
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V[s] = V[t];
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nv--;
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count = 2 * nv;
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}
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}
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indices.Reverse();//翻转法线
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return indices.ToArray();
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}
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private float Area()
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{
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int n = m_points.Count;
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float A = 0.0f;
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for (int p = n - 1, q = 0; q < n; p = q++)
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{
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Vector2 pval = m_points[p];
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Vector2 qval = m_points[q];
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A += pval.x * qval.y - qval.x * pval.y;//两向量叉乘只取z值，如果为负则顺时针
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}
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return (A * 0.5f);
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}
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private bool Snip(int u, int v, int w, int n, int[] V)
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{
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int p;
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Vector2 A = m_points[V[u]];
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Vector2 B = m_points[V[v]];
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Vector2 C = m_points[V[w]];
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if (Mathf.Epsilon > (((B.x - A.x) * (C.y - A.y)) - ((B.y - A.y) * (C.x - A.x))))//判断三点是否为顺时针排列，如果是的话是凹陷，不计算三角
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return false;
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for (p = 0; p < n; p++)
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{
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if ((p == u) || (p == v) || (p == w))
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continue;
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Vector2 P = m_points[V[p]];
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if (InsideTriangle(A, B, C, P))//是否有其他的点在三角形内部，是，不计算三角
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return false;
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}
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return true;
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}
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private bool InsideTriangle(Vector2 A, Vector2 B, Vector2 C, Vector2 P)
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{
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float ax, ay, bx, by, cx, cy, apx, apy, bpx, bpy, cpx, cpy;
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float cCROSSap, bCROSScp, aCROSSbp;
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ax = C.x - B.x; ay = C.y - B.y;
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bx = A.x - C.x; by = A.y - C.y;
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cx = B.x - A.x; cy = B.y - A.y;
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apx = P.x - A.x; apy = P.y - A.y;
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bpx = P.x - B.x; bpy = P.y - B.y;
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cpx = P.x - C.x; cpy = P.y - C.y;
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aCROSSbp = ax * bpy - ay * bpx;
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cCROSSap = cx * apy - cy * apx;
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bCROSScp = bx * cpy - by * cpx;
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return ((aCROSSbp >= 0.0f) && (bCROSScp >= 0.0f) && (cCROSSap >= 0.0f));//都是逆时针，P在ABC内
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}
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} |