Unity 实现Mesh切割的主要原理

变成一棵树 · 发表于 2023-3-31 19:09

Unity是一款非常流行的游戏引擎，它具有强大的3D建模和渲染功能，同时也支持Mesh切割。Mesh切割是指将一个Mesh对象切割成多个部分，这在游戏中经常用于实现物体的破碎效果、武器的攻击效果等。本文将详细讲解Unity实现Mesh切割的主要原理，并给出完整的代码实现。

Mesh切割的原理

代码实现

下面是Unity实现Mesh切割的完整代码，其中包括了计算切割平面、计算切割后的Mesh和生成新的Mesh对象等步骤。
using UnityEngine;

public class MeshCutter : MonoBehaviour {
// 要切割的Mesh对象
public Mesh meshToCut;
// 切割平面的法向量
public Vector3 planeNormal;
// 切割平面上的一点
public Vector3 planePoint;

// 切割后的Mesh对象
private Mesh[] cutMeshes;

// 切割Mesh对象
public void CutMesh() {
      // 计算切割平面
      Plane cuttingPlane = new Plane(planeNormal, planePoint);

      // 计算切割后的Mesh
      cutMeshes = MeshCut.Cut(meshToCut, cuttingPlane);

      // 生成新的Mesh对象
      for (int i = 0; i < cutMeshes.Length; i++) {
         GameObject obj = new GameObject(&#34;Cut Mesh&#34;);
         obj.AddComponent<MeshFilter>().mesh = cutMeshes;
         obj.AddComponent<MeshRenderer>().material = GetComponent<MeshRenderer>().material;
      }
}
}

public static class MeshCut {
public static Mesh[] Cut(Mesh mesh, Plane cuttingPlane) {
      // 初始化切割后的Mesh数组
      Mesh[] cutMeshes = new Mesh[2];
      cutMeshes[0] = new Mesh();
      cutMeshes[1] = new Mesh();

      // 获取原始Mesh的顶点和三角形面片信息
      Vector3[] vertices = mesh.vertices;
      int[] triangles = mesh.triangles;

      // 初始化切割后的Mesh的顶点和三角形面片信息
      Vector3[] cutVertices1 = new Vector3[vertices.Length];
      Vector3[] cutVertices2 = new Vector3[vertices.Length];
      int[] cutTriangles1 = new int[triangles.Length];
      int[] cutTriangles2 = new int[triangles.Length];
      int cutVerticesCount1 = 0, cutVerticesCount2 = 0;
      int cutTrianglesCount1 = 0, cutTrianglesCount2 = 0;

      // 遍历所有的三角形面片
      for (int i = 0; i < triangles.Length; i += 3) {
         // 获取三角形面片的顶点
         Vector3 v1 = vertices[triangles];
         Vector3 v2 = vertices[triangles[i + 1]];
         Vector3 v3 = vertices[triangles[i + 2]];

         // 判断三角形面片是否与切割平面相交
         bool v1Side = cuttingPlane.GetSide(v1);
         bool v2Side = cuttingPlane.GetSide(v2);
         bool v3Side = cuttingPlane.GetSide(v3);

         // 三角形面片与切割平面相交
         if (v1Side != v2Side || v2Side != v3Side) {
            // 计算相交点
            Vector3 v1v2 = v2 - v1;
            Vector3 v1v3 = v3 - v1;
            Vector3 planeNormal = cuttingPlane.normal;
            float distance = cuttingPlane.distance;
            float t1 = (distance - Vector3.Dot(planeNormal, v1)) / Vector3.Dot(planeNormal, v1v2);
            float t2 = (distance - Vector3.Dot(planeNormal, v1)) / Vector3.Dot(planeNormal, v1v3);
            Vector3 p1 = v1 + t1 * v1v2;
            Vector3 p2 = v1 + t2 * v1v3;

            // 判断相交点在哪个半球中，并将相交点添加到对应的Mesh中
            if (v1Side) {
                  cutVertices1[cutVerticesCount1] = v1;
                  cutVertices1[cutVerticesCount1 + 1] = p1;
                  cutVertices1[cutVerticesCount1 + 2] = p2;

                  cutVertices2[cutVerticesCount2] = p1;
                  cutVertices2[cutVerticesCount2 + 1] = p2;
                  cutVertices2[cutVerticesCount2 + 2] = v3;

                  cutTriangles1[cutTrianglesCount1] = cutVerticesCount1;
                  cutTriangles1[cutTrianglesCount1 + 1] = cutVerticesCount1 + 1;
                  cutTriangles1[cutTrianglesCount1 + 2] = cutVerticesCount1 + 2;

                  cutTriangles2[cutTrianglesCount2] = cutVerticesCount2;
                  cutTriangles2[cutTrianglesCount2 + 1] = cutVerticesCount2 + 1;
                  cutTriangles2[cutTrianglesCount2 + 2] = cutVerticesCount2 + 2;

                  cutVerticesCount1 += 3;
                  cutVerticesCount2 += 3;
                  cutTrianglesCount1 += 3;
                  cutTrianglesCount2 += 3;
            }
            else {
                  cutVertices2[cutVerticesCount2] = v1;
                  cutVertices2[cutVerticesCount2 + 1] = p1;
                  cutVertices2[cutVerticesCount2 + 2] = p2;

                  cutVertices1[cutVerticesCount1] = p1;
                  cutVertices1[cutVerticesCount1 + 1] = p2;
                  cutVertices1[cutVerticesCount1 + 2] = v3;

                  cutTriangles1[cutTrianglesCount1] = cutVerticesCount1;
                  cutTriangles1[cutTrianglesCount1 + 1] = cutVerticesCount1 + 1;
                  cutTriangles1[cutTrianglesCount1 + 2] = cutVerticesCount1 + 2;

                  cutTriangles2[cutTrianglesCount2] = cutVerticesCount2;
                  cutTriangles2[cutTrianglesCount2 + 1] = cutVerticesCount2 + 1;
                  cutTriangles2[cutTrianglesCount2 + 2] = cutVerticesCount2 + 2;

                  cutVerticesCount1 += 3;
                  cutVerticesCount2 += 3;
                  cutTrianglesCount1 += 3;
                  cutTrianglesCount2 += 3;
            }
         }
         // 三角形面片与切割平面不相交
         else {
            // 将三角形面片添加到对应的Mesh中
            if (v1Side) {
                  cutVertices1[cutVerticesCount1] = v1;
                  cutVertices1[cutVerticesCount1 + 1] = v2;
                  cutVertices1[cutVerticesCount1 + 2] = v3;

                  cutTriangles1[cutTrianglesCount1] = cutVerticesCount1;
                  cutTriangles1[cutTrianglesCount1 + 1] = cutVerticesCount1 + 1;
                  cutTriangles1[cutTrianglesCount1 + 2] = cutVerticesCount1 + 2;

                  cutVerticesCount1 += 3;
                  cutTrianglesCount1 += 3;
            }
            else {
                  cutVertices2[cutVerticesCount2] = v1;
                  cutVertices2[cutVerticesCount2 + 1] = v2;
                  cutVertices2[cutVerticesCount2 + 2] = v3;

                  cutTriangles2[cutTrianglesCount2] = cutVerticesCount2;
                  cutTriangles2[cutTrianglesCount2 + 1] = cutVerticesCount2 + 1;
                  cutTriangles2[cutTrianglesCount2 + 2] = cutVerticesCount2 + 2;

                  cutVerticesCount2 += 3;
                  cutTrianglesCount2 += 3;
            }
         }
      }

      // 设置切割后的Mesh的顶点和三角形面片信息
      cutMeshes[0].vertices = cutVertices1;
      cutMeshes[0].triangles = cutTriangles1;
      cutMeshes[1].vertices = cutVertices2;
      cutMeshes[1].triangles = cutTriangles2;

      // 返回切割后的Mesh数组
      return cutMeshes;
}
}

总结
本文详细讲解了Unity实现Mesh切割的主要原理，并给出了完整的代码实现。通过本文的学习，读者可以了解到Mesh切割的基本原理和实现方法，在游戏开发中可以根据需求自行实现Mesh切割功能。
对啦！这里有个游戏开发交流小组里面聚集了一帮热爱学习游戏的零基础小白，也有一些正在从事游戏开发的技术大佬，欢迎你来交流学习。

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Unity 实现Mesh切割的主要原理

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