初识Unity Mesh

Mesh概念：Mesh是Unity中的一个组件，称为网格组件。通俗的讲，Mesh是指模型的网格，3D模型是由多边形拼接而成，而多边形实际上是由多个三角形拼接而成的。所以一个3D模型的表面其实是由多个彼此相连的三角面构成。三维空间中，构成这些三角形的点和边的集合就是Mesh。

Mesh组成：

1、顶点坐标数组vertexes 

2、顶点在uv坐标系中的位置信息数组uvs

3、三角形顶点顺时针或者逆时针索引数组triangles

4、MeshFiler组件，用于增加mesh属性

5、MeshRender组件，增加材质并渲染出来。

6、可能还需要每个顶点的法线的数组normals

using UnityEngine;
using UnityEditor;
using System.Collections;

public class GenMesh
{
    [MenuItem("GameEditor/scene/Weather/GenMesh")]
    static public void GenMeshM()
    {
        Mesh m1 = CreateRect();
        AssetDatabase.CreateAsset(m1, "Assets/_Resource/model/prefab/weather/m1.asset");
    }

    public static Mesh CreateRect()
    {
        Mesh mesh = new Mesh();

        int particleNum = 10;
        //顶点坐标
        Vector3[] verts = new Vector3[4 * particleNum]; 
        //uv坐标
        Vector2[] uvs = new Vector2[4 * particleNum];
        //三角形索引
        int[] tris = new int[2 * 3 * particleNum];

        Vector3 position;
        for (int i = 0; i < particleNum; i++)
        {
            int i4 = i * 4;
            int i6 = i * 6;

            position.x = 5 * i;
            position.y = 5 * i;
            position.z = 0;

            //顶点坐标
            verts[i4 + 0] = position;
            verts[i4 + 1] = position + new Vector3(2, 0, 0);
            verts[i4 + 2] = position + new Vector3(2, 2, 0);
            verts[i4 + 3] = position + new Vector3(0, 2, 0);

            //四个顶点在UV坐标系中的位置
            uvs[i4 + 0] = new Vector2(0.0f, 0.0f);
            uvs[i4 + 1] = new Vector2(1.0f, 0.0f);
            uvs[i4 + 2] = new Vector2(1.0f, 1.0f);
            uvs[i4 + 3] = new Vector2(0.0f, 1.0f);

            //顺时针绘制三角形0 1 2 / 0 2 3
            tris[i6 + 0] = i4 + 0;
            tris[i6 + 1] = i4 + 1;
            tris[i6 + 2] = i4 + 2;
            tris[i6 + 3] = i4 + 0;
            tris[i6 + 4] = i4 + 2;
            tris[i6 + 5] = i4 + 3;
        }

        mesh.vertices = verts;
        mesh.triangles = tris;
        mesh.uv = uvs;
        mesh.RecalculateBounds();

        return mesh;
    }

    public static Mesh CreateCircle()
    {
        Mesh mesh = new Mesh();

        int particleNum = 10;
        Vector3[] verts = new Vector3[4 * particleNum];
        Vector2[] uvs = new Vector2[4 * particleNum];
        int[] tris = new int[2 * 3 * particleNum];

        Vector3 position;
        for (int i = 0; i < particleNum; i++)
        {
            int i4 = i * 4;
            int i6 = i * 6;

            position.x = 5 * i;
            position.y = 5 * i;
            position.z = 0;

            verts[i4 + 0] = position;
            verts[i4 + 1] = position + new Vector3(2, 0, 0);
            verts[i4 + 2] = position + new Vector3(2, 2, 0);
            verts[i4 + 3] = position + new Vector3(0, 2, 0);

            uvs[i4 + 0] = new Vector2(0.0f, 0.0f);
            uvs[i4 + 1] = new Vector2(1.0f, 0.0f);
            uvs[i4 + 2] = new Vector2(1.0f, 1.0f);
            uvs[i4 + 3] = new Vector2(0.0f, 1.0f);

            //顺时针绘制三角形0 1 2 / 0 2 3
            tris[i6 + 0] = i4 + 0;
            tris[i6 + 1] = i4 + 1;
            tris[i6 + 2] = i4 + 2;
            tris[i6 + 3] = i4 + 0;
            tris[i6 + 4] = i4 + 2;
            tris[i6 + 5] = i4 + 3;
        }

        mesh.vertices = verts;
        mesh.triangles = tris;
        mesh.uv = uvs;
        mesh.RecalculateBounds();

        return mesh;
    }
}

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