Unity3D之Mesh（五）绘制圆

前言：

Unity3D中Mesh的基本单位是三角形，而圆形就是由许许多多的三角形组成的。那么我们就知道了绘制圆形的Mesh需要两个变量：圆的半径  以及分割数；

基本过程与之前的类似，最基本的依然是顶点以及三角形索引数组，即：我们需要根据圆的半径以及预备的分割数，通过算法得到：顶点的Vector3数组 以及对应的三角形索引数组；

1、基本的程序实现架构如下：

using UnityEngine;

[RequireComponent(typeof(MeshRenderer), typeof(MeshFilter))]
public class yuan : MonoBehaviour
{

    public float Radius = 6;    //半径
    public int Segments = 60;   //分割数  

    private MeshFilter meshFilter;

    void Start()
    {

        meshFilter = GetComponent<MeshFilter>();
        meshFilter.mesh = CreateMesh(Radius, Segments);
    }

    Mesh CreateMesh(float radius, int segments)
    {
        Mesh mesh = new Mesh();
        return mesh;
    }
}

2、接下来就需要实现CreateMesh（）函数的基本功能（下述的程序包含该函数功能的实现）；整个程序的代码如下：

using UnityEngine;

[RequireComponent(typeof(MeshRenderer), typeof(MeshFilter))]
public class yuan : MonoBehaviour
{
    public float Radius = 6;    //半径
    public int Segments = 60;   //分割数
    private MeshFilter meshFilter;

    void Start()
    {
        meshFilter = GetComponent<MeshFilter>();
        meshFilter.mesh = CreateMesh(Radius, Segments);
    }

    Mesh CreateMesh(float radius, int segments)
    {
        //vertices:
        int vertices_count = Segments + 1;
        Vector3[] vertices = new Vector3[vertices_count];
        vertices[0] = Vector3.zero;
        float angledegree = 360.0f;
        float angleRad = Mathf.Deg2Rad * angledegree;
        float angleCur = angleRad;
        float angledelta = angleRad / Segments;
        for(int i=1;i< vertices_count; i++)
        {
            float cosA = Mathf.Cos(angleCur);
            float sinA = Mathf.Sin(angleCur);

            vertices[i] = new Vector3(Radius * cosA, 0, Radius * sinA);
            angleCur -= angledelta;
        }

        //triangles
        int triangle_count = segments * 3;
        int[] triangles = new int[triangle_count];
        for(int i=0,vi=1;i<= triangle_count-1;i+=3,vi++)     //因为该案例分割了60个三角形，故最后一个索引顺序应该是：0 60 1；所以需要单独处理
        {
            triangles[i] = 0;
            triangles[i + 1] = vi;
            triangles[i + 2] = vi + 1;
        }
        triangles[triangle_count - 3] = 0;
        triangles[triangle_count - 2] = vertices_count - 1;
        triangles[triangle_count - 1] = 1;                  //为了完成闭环，将最后一个三角形单独拎出来

        //uv:
        Vector2[] uvs = new Vector2[vertices_count];
        for (int i = 0; i < vertices_count; i++)
        {
            uvs[i] = new Vector2(vertices[i].x / radius / 2 + 0.5f, vertices[i].z / radius / 2 + 0.5f);
        }

        //负载属性与mesh
        Mesh mesh = new Mesh();
        mesh.vertices = vertices;
        mesh.triangles = triangles;
        mesh.uv = uvs;
        return mesh;
    }
}

3、效果图：

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