public static H3.Cell[] CalcCells2( Sphere[] mirrors, H3.Cell[] cells, Settings settings )
{
HashSet<Vector3D> completedCellIds = new HashSet<Vector3D>( cells.Select( c => c.ID ).ToArray() );
List<H3.Cell> completedCells = new List<H3.Cell>( cells );
ReflectCellsRecursive2( mirrors, cells, settings, completedCells, completedCellIds );
return completedCells.ToArray();
}