//PlaneBuilder.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

#region Editor

#if UNITY_EDITOR

using UnityEditor;

[CustomEditor(typeof(PlaneBuilder))]
public class PlaneBuilderEditor : Editor
{
 public override void OnInspectorGUI()
 {
 PlaneBuilder builder = (PlaneBuilder)target;

 EditorGUI.BeginChangeCheck();

 base.OnInspectorGUI();

 if (EditorGUI.EndChangeCheck())
 {
  builder.UpdateMesh();
 }

 if (GUILayout.Button("更新網(wǎng)格"))
 {
  builder.UpdateMesh();
 }
 }
}

#endif

#endregion Editor

[RequireComponent(typeof(MeshFilter), typeof(MeshRenderer))]
public class PlaneBuilder : MonoBehaviour
{
 [SerializeField]
 private MeshFilter _meshFilter;

 [SerializeField]
 private MeshRenderer _meshRenderer;

 /// <summary>
 /// 單元格大小
 /// </summary>
 [SerializeField]
 private Vector2 _cellSize = new Vector2(1, 1);

 /// <summary>
 /// 網(wǎng)格大小
 /// </summary>
 [SerializeField]
 private Vector2Int _gridSize = new Vector2Int(2, 2);

 public MeshRenderer MeshRenderer
 {
 get
 {
  return _meshRenderer;
 }
 }

 public MeshFilter MeshFilter
 {
 get
 {
  return _meshFilter;
 }
 }

 private void Awake()
 {
 _meshFilter = GetComponent<MeshFilter>();
 _meshRenderer = GetComponent<MeshRenderer>();
 UpdateMesh();
 }

 public void UpdateMesh()
 {
 Mesh mesh = new Mesh();

 //計算Plane大小
 Vector2 size;
 size.x = _cellSize.x * _gridSize.x;
 size.y = _cellSize.y * _gridSize.y;

 //計算Plane一半大小
 Vector2 halfSize = size / 2;

 //計算頂點及UV
 List<Vector3> vertices = new List<Vector3>();
 List<Vector2> uvs = new List<Vector2>();

 Vector3 vertice = Vector3.zero;
 Vector2 uv = Vector3.zero;

 for (int y = 0; y < _gridSize.y + 1; y++)
 {
  vertice.z = y * _cellSize.y - halfSize.y;//計算頂點Y軸
  uv.y = y * _cellSize.y / size.y;//計算頂點紋理坐標(biāo)V

  for (int x = 0; x < _gridSize.x + 1; x++)
  {
  vertice.x = x * _cellSize.x - halfSize.x;//計算頂點X軸
  uv.x = x * _cellSize.x / size.x;//計算頂點紋理坐標(biāo)U

  vertices.Add(vertice);//添加到頂點數(shù)組
  uvs.Add(uv);//添加到紋理坐標(biāo)數(shù)組
  }
 }

 //頂點序列
 int a = 0;
 int b = 0;
 int c = 0;
 int d = 0;
 int startIndex = 0;
 int[] indexs = new int[_gridSize.x * _gridSize.y * 2 * 3];//頂點序列
 for (int y = 0; y < _gridSize.y; y++)
 {
  for (int x = 0; x < _gridSize.x; x++)
  {
  //四邊形四個頂點
  a = y * (_gridSize.x + 1) + x;//0
  b = (y + 1) * (_gridSize.x + 1) + x;//1
  c = b + 1;//2
  d = a + 1;//3

  //計算在數(shù)組中的起點序號
  startIndex = y * _gridSize.x * 2 * 3 + x * 2 * 3;

  //左上三角形
  indexs[startIndex] = a;//0
  indexs[startIndex + 1] = b;//1
  indexs[startIndex + 2] = c;//2

  //右下三角形
  indexs[startIndex + 3] = c;//2
  indexs[startIndex + 4] = d;//3
  indexs[startIndex + 5] = a;//0
  }
 }

 //
 mesh.SetVertices(vertices);//設(shè)置頂點
 mesh.SetUVs(0, uvs);//設(shè)置UV
 mesh.SetIndices(indexs, MeshTopology.Triangles, 0);//設(shè)置頂點序列
 mesh.RecalculateNormals();
 mesh.RecalculateBounds();
 mesh.RecalculateTangents();

 _meshFilter.mesh = mesh;
 }

#if UNITY_EDITOR

 private void OnValidate()
 {
 if (null == _meshFilter)
 {
  _meshFilter = GetComponent<MeshFilter>();
 }
 if (null == _meshRenderer)
 {
  _meshRenderer = GetComponent<MeshRenderer>();
  if (null == _meshRenderer.sharedMaterial)
  {
  _meshRenderer.sharedMaterial = new Material(Shader.Find("Standard"));
  }
 }
 }

#endif
}