Unity3D之Mesh（五）繪制圓

前言：

Unity3D中Mesh的基本單位是三角形，而圓形就是由許許多多的三角形組成的。那么我們就知道了繪制圓形的Mesh需要兩個變量：圓的半徑  以及分割數；

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一、實現過程

基本過程與之前的類似，最基本的依然是頂點以及三角形索引數組，即：我們需要根據圓的半徑以及預備的分割數，通過算法得到：頂點的Vector3數組 以及對應的三角形索引數組；

1、基本的程序實現架構如下：

using UnityEngine;

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

    public float Radius = 6;    //半徑  
    public int Segments = 60;   //分割數  

    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、接下來就需要實現CreateMesh（）函數的基本功能（下述的程序包含該函數功能的實現）；整個程序的代碼如下：

using UnityEngine;

[RequireComponent(typeof(MeshRenderer), typeof(MeshFilter))]
public class yuan : MonoBehaviour
{
    public float Radius = 6;    //半徑  
    public int Segments = 60;   //分割數  
    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++)     //因為該案例分割了60個三角形，故最后一個索引順序應該是：0 60 1；所以需要單獨處理
        {
            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;                  //為了完成閉環，將最后一個三角形單獨拎出來

        //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);
        }

        //負載屬性與mesh
        Mesh mesh = new Mesh();
        mesh.vertices = vertices;
        mesh.triangles = triangles;
        mesh.uv = uvs;
        return mesh;
    }
}

3、效果圖：

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碰到的小知識：

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