using UnityEngine;
using System.Collections;

/*僅僅建立Mesh
 *
 *
 */
public class CreatMesh : MonoBehaviour {

    private GameObject mMesh;
    private Material mMaterial;

    /*  Mesh屬性
     *      長寬
     *      段數
     *      高度
     *      高度差
     */
    private Vector2 size;//長度和寬度
    private float minHeight = -10;//最小高度
    private float maxHeight = 10;//最大高度
    private Vector2 segment;//長度的段數和寬度的段數
    private float unitH;//最小高度和最大高度只差，值為正

    /*  頂點屬性
     *      頂點
     *      uv
     *      三角形 
     */
    private Vector3[] vertexes;//頂點數
    private Vector2 uvs;//uvs座標
    private int[] triangles;//三角形索引

	void Start () {
        creatMesh(100, 100, 3, 3, -10, 10);
	}
	
    private void creatMesh(float width, float height, uint segmentX, uint segmentY,int min, int max)
    {
        size = new Vector2(width, height);
        maxHeight = max;
        minHeight = min;
        unitH = maxHeight - minHeight;
        segment = new Vector2(segmentX, segmentY);

        if (mMesh != null)
        {
            Destroy(mMesh);
        }
        mMesh = new GameObject();
        mMesh.name = "CreateMesh";

        computeVertexes();
        DrawMesh();
    }

    private void computeVertexes()
    {
        int sum = Mathf.FloorToInt((segment.x + 1) * (segment.y + 1));//頂點總數
        float w = size.x / segment.x;//每一段的長度
        float h = size.y / segment.y;
 
        GetTriangles();

        int index = 0;
        vertexes = new Vector3[sum];
        for (int i = 0; i < segment.y + 1;i++ )
        {
            for (int j = 0; j < segment.x + 1; j++)
            {
                float tempHeight = 0;
                vertexes[index] = new Vector3(j*w, 0, i*h);
                index++;
            }
        }
    }

    private void DrawMesh()
    {
        Mesh mesh = mMesh.AddComponent<MeshFilter>().mesh;//網格
        mMesh.AddComponent<MeshRenderer>();//網格渲染器

        mMaterial = new Material(Shader.Find("Diffuse"));//材質

        mMesh.GetComponent<Renderer>().material = mMaterial;

        /*設定mesh*/
        mesh.Clear();//更新
        mesh.vertices = vertexes;
        //mesh.uv 
        mesh.triangles = triangles;

        mesh.RecalculateNormals();
        mesh.RecalculateBounds();

    }

    private int[] GetTriangles()
    {
        int sum = Mathf.FloorToInt(segment.x * segment.y * 6);//三角形頂點總數
        triangles = new int[sum];
        uint index = 0;
        for (int i = 0; i < segment.y; i++)
        {
            for (int j = 0; j < segment.x; j++)
            {
                int role = Mathf.FloorToInt(segment.x) + 1;
                int self = j + (i * role);
                int next = j + ((i + 1) * role);
                //順時針
                triangles[index] = self;
                triangles[index + 1] = next + 1;
                triangles[index + 2] = self + 1;
                triangles[index + 3] = self;
                triangles[index + 4] = next;
                triangles[index + 5] = next + 1;
                index += 6;
            }
        }
        return triangles;
    }
}