/// <summary>
/// Subdivide this node along the principal axis of its child objects
/// </summary>
public void Subdivide()
{
if (_Children != null && _Children.Count > 1)
{
double max;
double min;
CoordinateAxis largest = LargestDimension(_Children, out min, out max);
int divisions = Math.Min(_Children.Count, Math.Min(_Tree.MaxDivisions, (int)Math.Floor(max - min / _Tree.MinCellSize) + 1));
if (divisions > 1)
{
_CellSize = (max - min) / (divisions - 1);
_Origin = min - _CellSize / 2;
_SplitDimension = largest;
_Branches = new DDTreeNode <T> [divisions];
//Add all children to branches:
foreach (T child in _Children)
{
AddToBranch(child, false);
}
//Subdivide children:
for (int i = 0; i < _Branches.Length; i++)
{
DDTreeNode <T> node = _Branches[i];
if (node != null &&
node.Children.Count < Children.Count)
{
node.Subdivide();
}
}
}
}
}
/// <summary>
/// Creates a new DDTree populated with the specified collection of objects
/// </summary>
/// <param name="items">The objects to include within the tree.</param>
/// <param name="maxDivisions">The maximum number of cells into which each
/// level in the tree should be divided</param>
/// <param name="minCellSize">The minimum allowable size of a cell. Once a node
/// reaches this size it will no longer subdivide regardless of how many items are
/// contained within it.</param>
/// <param name="maxLeafPopulation">The maximum population per leaf node. If the
/// number of objects within a cell exceeds this number and the minimum cell size
/// has not yet been reached, the node will subdivide</param>
protected DDTree(IList <T> items, int maxDivisions = 10,
double minCellSize = 1, int maxLeafPopulation = 4)
{
MaxDivisions = maxDivisions;
MinCellSize = minCellSize;
MaxLeafPopulation = maxLeafPopulation;
_RootNode = new DDTreeNode <T>(this);
foreach (T item in items)
{
_RootNode.Children.Add(item);
}
_RootNode.Subdivide();
}