int[][] MarkGroundUpper(int[][] map, int[][] upperMap)
{
for (int i = 0; i < map.Length; i++)
{
for (int j = 0; j < map[i].Length; j++)
{
if (!ChunkUtil.IsGroundIndex(map[i][j]))
{
upperMap[i][j] = -1;
}
}
}
return(upperMap);
}