//圓柱體是由兩個圓和一個長方形組成的 先輸入長方形的頂點 然后在輸入圓頂點
 private void UpdateMesh(Mesh mesh,int edg_x, int edg_y, float rad, float len)
 {
  edg_x = Mathf.Max(2, edg_x);//保證最低2個邊
  edg_y = Mathf.Max(2, edg_y);
  int _deglen = (edg_x +1)*edg_y;//長方體
  int totalcount = _deglen + (1 + edg_x + 1) * 2; //加兩個圓
 
 
  Vector3[] normals = new Vector3[totalcount];
  Vector3[] verts = new Vector3[totalcount];
  Vector2[] uvs = new Vector2[totalcount];
  int[] trians = new int[edg_x * edg_y*6]; 
  float reg = 6.28318f / edg_x;
  float _len = len / (edg_y - 1);
 
  
 
  for (int y = 0; y < edg_y; y++)
   for (int x = 0; x < edg_x + 1; x++)//多一個邊來保存UV值
   {
    int i = x + y * (edg_x + 1);
    verts[i] = new Vector3(Mathf.Sin((reg * (x % edg_x)) % 6.28318f) * rad, Mathf.Cos((reg * (x % edg_x)) % 6.28318f) * rad, rightPos + y * _len);//計算頂點坐標
    normals[i] = new Vector3(verts[i].x, verts[i].y, 0);//計算法線方向
    int id = x % (edg_x + 1) * 6 + y * edg_x * 6;
    if (x < edg_x + 1 && y < edg_y - 1 && (id + 5) < trians.Length)//計算頂點數(shù)組
    {
     if(length>0)
     {
      trians[id] = i;
      trians[id + 1] = trians[id + 4] = i + edg_x + 1;
      trians[id + 2] = trians[id + 3] = i + 1;
      trians[id + 5] = i + edg_x + 2;
     }
     else
     {
      trians[id] = i;
      trians[id + 1] = trians[id + 3] = i + 1;
      trians[id + 2]= trians[id + 5]=i + edg_x + 1;
      trians[id + 4] = i + edg_x + 2;
     }
     
    }
    //if (edg_x != 2)//計算UV，考慮到2個邊的情況
    // uvs[i] = new Vector2(x == edg_x ? 1f : quaduvStep.x * x, y == edg_y - 1 ? (2*rad+len)/totalLen : quaduvStep.y * y);
    //else
    // uvs[i] = new Vector2(x % edg_x, y == edg_y - 1 ? (2 * rad + len) / totalLen : quaduvStep.y * y);
   }
  
  int maxId = edg_x * (edg_y - 1) * 6;
  verts[_deglen] = new Vector3(0,0,rightPos);
  
  normals[_deglen] = -Vector3.forward;
 
  //uvs[_deglen] = new Vector2(0.5f, (rad) / totalLen);
  //原點一面
  for (int x = 0; x < edg_x+1 ; x++)
  {
   verts[_deglen + 1 + x] = new Vector3(Mathf.Sin((reg * (x % edg_x)) % 6.28318f) * rad, Mathf.Cos((reg * (x % edg_x)) % 6.28318f) * rad, rightPos);
   normals[_deglen + 1 + x] = -Vector3.forward;
   if (x == edg_x) continue;
 
   if(length>0)
   {
    trians[3 * x + maxId] = _deglen;
    trians[3 * x + 1 + maxId] = _deglen + 1 + x;
    trians[3 * x + 2 + maxId] = _deglen + 2 + x;
   }
   else
   {
    trians[3 * x + maxId] = _deglen;
    trians[3 * x + 1 + maxId] = _deglen + 2 + x;
    trians[3 * x + 2 + maxId] = _deglen + 1 + x;
   }
  }
 
 
  //遠點一面
  maxId += 3 * edg_x;
  verts[_deglen + 2 + edg_x] = new Vector3(0, 0, leftPos);
  normals[_deglen + 2 + edg_x] = Vector3.forward;
  //uvs[_deglen + 1] = new Vector2(0.5f, (3 * rad + len) / totalLen);
  
  for (int x = 0; x < edg_x+1; x++)
  {
   verts[1 + x+edg_x+2+ _deglen] =new Vector3(Mathf.Sin((reg * (x % edg_x)) % 6.28318f) * rad, Mathf.Cos((reg * (x % edg_x)) % 6.28318f) * rad,leftPos);
   normals[1 + x + edg_x + 2 + _deglen] = Vector3.forward;
   if (x == edg_x) continue;
   if (length > 0)
   {
    trians[3 * x + maxId] = _deglen + 2 + edg_x;
    trians[3 * x + 1 + maxId] = _deglen + 2 + edg_x + x + 2;
    trians[3 * x + 2 + maxId] = _deglen + 2 + edg_x + x + 1;
   }
   else
   {
    trians[3 * x + maxId] = _deglen + 2 + edg_x;
    trians[3 * x + 1 + maxId] = _deglen + 2 + edg_x + x + 1;
    trians[3 * x + 2 + maxId] = _deglen + 2 + edg_x + x + 2;
   }
  }
  mesh.Clear();
  mesh.vertices = verts;
  mesh.triangles = trians;
  //mesh.uv = uvs;
  mesh.normals = normals;
  mesh.RecalculateBounds();
 }