void DepthSort()
{
var st = new SortTool <BaseUnit>();
foreach (var ub in _unitList)
{
st.AddItem((int)(ub.SortValue * 100), ub);
}
var sortList = st.Sort(true);
for (int i = 0; i < sortList.Length; i++)
{
sortList[i].SetSortValue(i);
}
}
