using System.Collections;

using System.Collections.Generic;

using UnityEngine;

//创建球形mesh

public class BallCreater : MonoBehaviour {

    public Material ballMat;//材质

	void Start () {

        createBall("mEarth",new Vector3(0,0,0),100.0f,181,88);

    }

    void Update () {

	}

    /// <summary>

    /// 创建球形mesh

    /// </summary>

    /// <param name="meshName">名称</param>

    /// <param name="center">球心</param>

    /// <param name="radius">半径</param>

    /// <param name="longPart">经线数</param>

    /// <param name="latPart">纬线数</param>

    /// <returns></returns>

    private GameObject createBall(string meshName,Vector3 center, float radius, int longPart, int latPart)

    {

        GameObject meshObject = new GameObject(meshName);

        int verticeNum = longPart * latPart+2* longPart;//经线数*纬线数+极点处多个重合点 (首尾经线重合)

        Vector3[] vertices = new Vector3[verticeNum];//顶点数组

        Vector3[] normals = new Vector3[verticeNum];//顶点法线数组

        Vector2[] uvs = new Vector2[verticeNum];//uv数组

        int[] triangles = new int[(longPart-1)* latPart * 3 * 2];//三角集合数组,保存顶点索引 

        float degreesToRadians = Mathf.PI / 180.0f; //弧度转换

        float deltaLong = 360.0f /(longPart-1);//经度每份对应度数

        float deltaLat = 180.0f/ (latPart+2);//纬度每份对应度数

        //极点放置多个顶点，同位置不同uv

        for (int i = 0; i < longPart; i++)

        {

            vertices[i] = new Vector3(0, 0, 1) * radius;

            normals[i] = vertices[0].normalized;

            uvs[i] = new Vector2((float)i/(float)longPart,0);

        }

        int k = 0;

        for (int i = 0; i < longPart-1; i++)

        {

            triangles[k++] = i;

            triangles[k++] = i+ longPart;

            triangles[k++] = i + longPart+1;

        }

        for (int tempLat = 0; tempLat < latPart; tempLat++)

        {

            float tempAngle1 = ((tempLat+1)* deltaLat) * degreesToRadians;

            for (int tempLong = 0; tempLong < longPart; tempLong++)

            {

                float tempAngle2 = (tempLong*deltaLong) * degreesToRadians;

                int tempIndex = tempLong+ tempLat* longPart+ longPart;

                vertices[tempIndex] = new Vector3(Mathf.Sin(tempAngle1) * Mathf.Cos(tempAngle2), Mathf.Sin(tempAngle1) * Mathf.Sin(tempAngle2), Mathf.Cos(tempAngle1)) * radius;

                normals[tempIndex] = vertices[tempIndex].normalized;

                uvs[tempIndex] = new Vector2((float)tempLong / (float)longPart, (float)tempLat / (float)latPart);

                if (tempLat!= latPart-1)

                {

                    if (tempLong != longPart-1)

                    {

                        triangles[k++] = tempLong + tempLat * longPart + longPart;

                        triangles[k++] = tempLong + tempLat * longPart + 2 * longPart;

                        triangles[k++] = tempLong + tempLat * longPart + longPart + 1;

                        triangles[k++] = tempLong + tempLat * longPart + 2 * longPart;

                        triangles[k++] = tempLong + tempLat * longPart + 1 + 2 * longPart;

                        triangles[k++] = tempLong + tempLat * longPart + 1 + longPart;

                    }

                }

            }

        }

        //极点放置多个顶点，同位置不同uv

        for (int i = 0; i < longPart; i++)

        {

            vertices[verticeNum - 1-i] = new Vector3(0, 0, -1) * radius;

            normals[verticeNum - 1-i] = vertices[verticeNum - 1].normalized;

            uvs[verticeNum - 1-i] = new Vector2(1.0f-(float)i / (float)longPart, 1.0f);

        }

        for (int i = 0; i < longPart-1; i++)

        {

            triangles[k++] = verticeNum - 1-i;

            triangles[k++] = verticeNum - 1-i- longPart;

            triangles[k++] = verticeNum - 2 - i- longPart;

        } 

        Mesh mesh = new Mesh();

        mesh.vertices = vertices;

        mesh.triangles = triangles;

        mesh.normals = normals;

        mesh.uv = uvs;

        mesh.RecalculateBounds();

        mesh.RecalculateNormals();

        meshObject.AddComponent<MeshFilter>();

        meshObject.AddComponent<MeshRenderer>();

        meshObject.GetComponent<MeshFilter>().mesh = mesh;

        meshObject.GetComponent<MeshRenderer>().material = ballMat;

        meshObject.transform.position += center;

        return meshObject;

    }

}