unity之不规则多边形uv贴图

快来打我* 2022-09-19 01:26 277阅读 0赞

mesh的uv贴图想必大家都知道是三角形组成原理，我使用三角剖分的方法去解决不规则多边形的uv贴图，

三角剖分算法大家可以百度上去看，很多种教程，具体脚本算法如下：

using UnityEngine;
    using System.Collections;
    using System.Collections.Generic;
    
    public class TriangleSubdivision  :MonoBehaviour{
    	public static int[] TriangulatePolygon (Vector2[] XZofVertices) {
    		int VertexCount = XZofVertices.Length;
            float xmin = XZofVertices[0].x;
            float ymin = XZofVertices[0].y;
            float xmax = xmin;
            float ymax = ymin;
            for (int ii1 = 1; ii1 < VertexCount; ii1++)
            {
    			if (XZofVertices[ii1].x < xmin) 
    			{ 
    				xmin = XZofVertices[ii1].x; 
    			}
    			else if (XZofVertices[ii1].x > xmax) 
    			{
    				xmax = XZofVertices[ii1].x; 
    			}
    			if (XZofVertices[ii1].y < ymin) 
    			{ 
    				ymin = XZofVertices[ii1].y; 
    			}
    			else if (XZofVertices[ii1].y > ymax) 
    			{ 
    				ymax = XZofVertices[ii1].y;
    			}
            }
            float dx = xmax - xmin;
            float dy = ymax - ymin;
            float dmax = (dx > dy) ? dx : dy;
            float xmid = (xmax + xmin) * 0.5f;
            float ymid = (ymax + ymin) * 0.5f;
            Vector2[] ExpandedXZ = new Vector2[3 + VertexCount];
            for (int ii1 = 0; ii1 < VertexCount; ii1++)
            {
    			ExpandedXZ[ii1] = XZofVertices[ii1];
            }
    		//外接三角形的三个点
    		ExpandedXZ[VertexCount] = new Vector2((xmid - 2 * dmax), (ymid - dmax));
            ExpandedXZ[VertexCount + 1] = new Vector2(xmid, (ymid + 2 * dmax));
            ExpandedXZ[VertexCount + 2] = new Vector2((xmid + 2 * dmax), (ymid - dmax));
    		List<Triangle> TriangleList = new List<Triangle>();
            TriangleList.Add(new Triangle(VertexCount, VertexCount+1, VertexCount+2));
            for (int ii1 = 0; ii1 < VertexCount; ii1++)
            {
    			List<Edge> Edges = new List<Edge>();
    			for (int ii2 = 0; ii2 < TriangleList.Count; ii2++)
    			{
    				if (TriangulatePolygonSubFunc_InCircle(ExpandedXZ[ii1], ExpandedXZ[TriangleList[ii2].p1],ExpandedXZ[TriangleList[ii2].p2],ExpandedXZ[TriangleList[ii2].p3]))
    				{
    					Edges.Add(new Edge(TriangleList[ii2].p1, TriangleList[ii2].p2));
    		            Edges.Add(new Edge(TriangleList[ii2].p2, TriangleList[ii2].p3));
    		            Edges.Add(new Edge(TriangleList[ii2].p3, TriangleList[ii2].p1));
    		            TriangleList.RemoveAt(ii2);
    		            ii2--;
    				}
    			}
    			if (ii1 >= VertexCount) { continue; }
    			for (int ii2 = Edges.Count - 2; ii2 >= 0; ii2--)
    			{
    				for (int ii3 = Edges.Count - 1; ii3 >= ii2 + 1; ii3--)
    				{
    					if (Edges[ii2].Equals(Edges[ii3]))
    					{
    						Edges.RemoveAt(ii3);
    						Edges.RemoveAt(ii2);
                            ii3--;
                            continue;
    					}
    				}
    			}
    			for (int ii2 = 0; ii2 < Edges.Count; ii2++)
                {
    				TriangleList.Add(new Triangle(Edges[ii2].p1, Edges[ii2].p2, ii1));
    			}
                Edges.Clear();
                Edges = null;
    		}
    		//大于点集外围的点 外接三角形的三个确认点
            for (int ii1 = TriangleList.Count - 1; ii1 >= 0; ii1--)
            {
    			if (TriangleList[ii1].p1 >= VertexCount ||TriangleList[ii1].p2 >= VertexCount ||TriangleList[ii1].p3 >= VertexCount)
                { 
    				TriangleList.RemoveAt(ii1); 
    			}
            }
    		//不在点集区域内的面
    		for(int ii3 = 0;ii3<TriangleList.Count;ii3++){
    			if(TriangleInPolygonOuter(XZofVertices,XZofVertices[TriangleList[ii3].p1],XZofVertices[TriangleList[ii3].p2],XZofVertices[TriangleList[ii3].p3])){
    				TriangleList.RemoveAt(ii3);
    				ii3--;
    			}
    		}
            TriangleList.TrimExcess();
            int[] Triangles = new int[3 * TriangleList.Count];
            for (int ii1 = 0; ii1 < TriangleList.Count; ii1++)
            {
    			Triangles[3 * ii1] = TriangleList[ii1].p1;
    	        Triangles[3 * ii1 + 1] = TriangleList[ii1].p2;
    	        Triangles[3 * ii1 + 2] = TriangleList[ii1].p3;
            }
    		return Triangles;
    	}

// float.Epsilon这个值为无限接近于0的值，我再pc上正常，在ios端就不能用了，我打印出直接输出0，大家可以模拟一个值，0.0000000001，或者什么   趋近于0，但不等于0就行了，
    	static bool TriangulatePolygonSubFunc_InCircle(Vector2 p, Vector2 p1, Vector2 p2, Vector2 p3) {
    		if (Mathf.Abs(p1.y - p2.y) < float.Epsilon &&Mathf.Abs(p2.y - p3.y) < float.Epsilon)
            { 
    			return false; 
    		}
            float m1, m2, mx1, mx2, my1, my2, xc, yc;
            if (Mathf.Abs(p2.y - p1.y) < float.Epsilon)
            {
    			m2 = -(p3.x - p2.x) / (p3.y - p2.y);
                mx2 = (p2.x + p3.x) * 0.5f;
                my2 = (p2.y + p3.y) * 0.5f;
                xc = (p2.x + p1.x) * 0.5f;
                yc = m2 * (xc - mx2) + my2;
            }
            else if (Mathf.Abs(p3.y - p2.y) < float.Epsilon)
            {
                m1 = -(p2.x - p1.x) / (p2.y - p1.y);
                mx1 = (p1.x + p2.x) * 0.5f;
                my1 = (p1.y + p2.y) * 0.5f;
                xc = (p3.x + p2.x) * 0.5f;
                yc = m1 * (xc - mx1) + my1;
            }
            else
            {
                m1 = -(p2.x - p1.x) / (p2.y - p1.y);
                m2 = -(p3.x - p2.x) / (p3.y - p2.y);
                mx1 = (p1.x + p2.x) * 0.5f;
                mx2 = (p2.x + p3.x) * 0.5f;
                my1 = (p1.y + p2.y) * 0.5f;
                my2 = (p2.y + p3.y) * 0.5f;
                xc = (m1 * mx1 - m2 * mx2 + my2 - my1) / (m1 - m2);
                yc = m1 * (xc - mx1) + my1;
            }
    		float dx = p2.x - xc;
            float dy = p2.y - yc;
            float rsqr = dx * dx + dy * dy;
            dx = p.x - xc;
            dy = p.y - yc;
            double drsqr = dx * dx + dy * dy;
            return (drsqr <= rsqr);
        }
    	static bool TriangleInPolygonOuter(Vector2[] pList,Vector2 p1,Vector2 p2,Vector2 p3){
    		Vector2 centrePoint = new Vector2((p1.x+p2.x+p3.x)/3,(p1.y+p2.y+p3.y)/3);
    		int crossNum = 0;
            for (int i = 0; i < pList.Length; i++)
            {
    			if (IsPointInLine(centrePoint.x, centrePoint.y, pList[i].x, pList[i].y, pList[(i+1)%pList.Length].x, pList[(i+1)%pList.Length].y)==0)
                {
                    crossNum=crossNum+1;
    				continue;
                }else if(IsPointInLine(centrePoint.x, centrePoint.y, pList[i].x, pList[i].y, pList[(i+1)%pList.Length].x, pList[(i+1)%pList.Length].y)==2){
    				crossNum = 1;
    				break;
    			}
            }
    		if ((crossNum % 2) == 0)
    		{
    			return true;
            }
    		crossNum = 0;
    //		}
            return false;
    	}
    	//0   在外  1  在内   2  边上
    	static int IsPointInLine(float x,float y,float x1,float y1,float x2,float y2)
        {
    		float maxY =y1;
            float minY = y2;
    		if(y1>y2){
    		    maxY = y1;
    			minY = y2;
    		}else{
    			maxY = y2;
    			minY = y1;
    		}
    		float averageX = (x1+x2)/2;
    		float averageY = (y1+y2)/2;
    		if(y==averageY&&x==averageX){
    			return 2;
    		}
            if (y < maxY && y >minY)
            {
                if (x >(x1 + (x2 - x1) * (y - y1) / (y2 - y1)))
                {
                    return 0;
                }
            }
            return 1;
        }
    }
     struct Triangle
    {
    	public int p1;
        public int p2;
        public int p3;
        public Triangle(int point1, int point2, int point3)
        {
    		p1 = point1; p2 = point2; p3 = point3;
        }
    }
    class Edge
    {
    	public int p1;
    	public int p2;
    	public Edge(int point1, int point2)
        {
    		p1 = point1; p2 = point2;
        }
    	public Edge() : this(0, 0)
        {}
    	public bool Equals(Edge other)
        {
    		return ((this.p1 == other.p2) && (this.p2 == other.p1)) ||((this.p1 == other.p1) && (this.p2 == other.p2));
        }
    }

使用也很方便，直接调用 TriangulatePolygon，传入你所设置点的坐标数组，它是二维的，返回的就是坐标数组对应的数组下标编号(mesh.triangles)数组，

三角剖分是利用图形外切圆，判断不在多边形内的三角面，使用引射线法，当然大家也可以使用其他的，在这里我使用的这种，具体朋友们可以自己模拟几个点去测试，

下一章我打算写弧形uv贴图，和弧形面贴图，先给出下一章的图形效果，不懂的大家可以随时讨论，由于自己写作水平有限，所以解释的不太清楚，大家可以随时找我讨论，

共同学习进步，相信你们了解了那几个算法后，这一看就明白了，可能也有我没考虑到的，欢迎大家踊跃提出你们的意见

![Image 1][]

![Center][]

[Image 1]: 
[Center]: /images/20220828/9c5f5bb5392d43fe840cf2662d485a25.png