根据Mesh模型的UV坐标获得这一点的法线和点坐标

分手后的思念是犯贱 2023-10-01 20:51 9阅读 0赞

这段代码经常用到，忘了从哪里复制过来的，经过了一些修改。

using System.Collections;
    using System.Collections.Generic;
    using UnityEngine;
    
    public class GameFun 
    {
        
    
        /// <summary>
        /// //UV坐标转换成3D坐标
        /// </summary>
        /// <param name="mesh">mesh模型</param>
        /// <param name="uv">uv点击坐标</param>
        /// <param name="normal">返回这一点的法线，注意没有标准化</param>
        /// <returns>返回模型坐标</returns>
        public static Vector3 UvTo3D(Mesh mesh, Vector2 uv, out Vector3 normal)
        {
        
            int[] tris = mesh.triangles;
            Vector2[] uvs = mesh.uv;
            Vector3[] verts = mesh.vertices;
            Vector3[] normals = mesh.normals;
            normal = Vector3.zero;
            for (int i = 0; i < tris.Length; i += 3)
            {
        
                //获得三角形三个顶点的UV坐标
                Vector2 u1 = uvs[tris[i]];
                Vector2 u2 = uvs[tris[i + 1]];
                Vector2 u3 = uvs[tris[i + 2]];
    
                float a = Area(u1, u2, u3); if (a == 0) continue;
    
                //计算u1, u2, u3的质心坐标  
                //如果有人是负数，则点在三角形外:跳过它
                float a1 = Area(u2, u3, uv) / a; if (a1 < 0) continue;
                float a2 = Area(u3, u1, uv) / a; if (a2 < 0) continue;
                float a3 = Area(u1, u2, uv) / a; if (a3 < 0) continue;
    
                //三角形内部的点-通过插值找到网格位置
                normal = (normals[tris[i]] + normals[tris[i + 1]] + normals[tris[i + 2]]) / 3f;
                Vector3 p3D = a1 * verts[tris[i]] + a2 * verts[tris[i + 1]] + a3 * verts[tris[i + 2]];
                // 这个是模型坐标,你可以通过TransformPoint转换成世界坐标;
                return p3D;
            }
    
            return Vector3.zero;
        }
    
    
        //使用“2D叉积”计算带符号的三角形面积:  
        static float Area(Vector2 p1, Vector2 p2, Vector2 p3)
        {
        
            Vector2 v1 = p1 - p3;
            Vector2 v2 = p2 - p3;
            return (v1.x * v2.y - v1.y * v2.x) / 2f;
        }
    }