/// <summary>
/// Splits the given node in two other nodes.
/// </summary>
/// <param name="node"></param>
/// <param name="minimumSize"></param>
/// <returns></returns>
private static Node[] SplitNode(Node node, int minimumSize)
{
bool leaf = (node.Children is List <T>);
// create the target nodes.
var nodes = new Node[2];
nodes[0] = new Node();
nodes[0].Boxes = new List <BoxF2D>();
if (leaf)
{
nodes[0].Children = new List <T>();
}
else
{
nodes[0].Children = new List <Node>();
}
nodes[1] = new Node();
nodes[1].Boxes = new List <BoxF2D>();
if (leaf)
{
nodes[1].Children = new List <T>();
}
else
{
nodes[1].Children = new List <Node>();
}
// select the seed boxes.
int[] seeds = RTreeMemoryIndex <T> .SelectSeeds(node.Boxes);
// add the boxes.
nodes[0].Boxes.Add(node.Boxes[seeds[0]]);
nodes[1].Boxes.Add(node.Boxes[seeds[1]]);
nodes[0].Children.Add(node.Children[seeds[0]]);
nodes[1].Children.Add(node.Children[seeds[1]]);
// create the boxes.
var boxes = new BoxF2D[2]
{
node.Boxes[seeds[0]], node.Boxes[seeds[1]]
};
node.Boxes.RemoveAt(seeds[0]); // seeds[1] is always < seeds[0].
node.Boxes.RemoveAt(seeds[1]);
node.Children.RemoveAt(seeds[0]);
node.Children.RemoveAt(seeds[1]);
while (node.Boxes.Count > 0)
{
// check if one of them needs em all!
if (nodes[0].Boxes.Count + node.Boxes.Count == minimumSize)
{ // all remaining boxes need te be assigned here.
for (int idx = 0; node.Boxes.Count > 0; idx++)
{
boxes[0] = boxes[0].Union(node.Boxes[0]);
nodes[0].Boxes.Add(node.Boxes[0]);
nodes[0].Children.Add(node.Children[0]);
node.Boxes.RemoveAt(0);
node.Children.RemoveAt(0);
}
}
else if (nodes[1].Boxes.Count + node.Boxes.Count == minimumSize)
{ // all remaining boxes need te be assigned here.
for (int idx = 0; node.Boxes.Count > 0; idx++)
{
boxes[1] = boxes[1].Union(node.Boxes[0]);
nodes[1].Boxes.Add(node.Boxes[0]);
nodes[1].Children.Add(node.Children[0]);
node.Boxes.RemoveAt(0);
node.Children.RemoveAt(0);
}
}
else
{ // choose one of the leaves.
int leafIdx;
int nextId = RTreeMemoryIndex <T> .PickNext(boxes, node.Boxes, out leafIdx);
boxes[leafIdx] = boxes[leafIdx].Union(node.Boxes[nextId]);
nodes[leafIdx].Boxes.Add(node.Boxes[nextId]);
nodes[leafIdx].Children.Add(node.Children[nextId]);
node.Boxes.RemoveAt(nextId);
node.Children.RemoveAt(nextId);
}
}
RTreeMemoryIndex <T> .SetParents(nodes[0]);
RTreeMemoryIndex <T> .SetParents(nodes[1]);
return(nodes);
}
/// <summary>
/// Adds the given item to the given box.
/// </summary>
/// <param name="leaf"></param>
/// <param name="box"></param>
/// <param name="item"></param>
/// <param name="minimumSize"></param>
/// <param name="maximumSize"></param>
private static Node Add(Node leaf, BoxF2D box, T item, int minimumSize, int maximumSize)
{
if (box == null)
{
throw new ArgumentNullException("box");
}
if (leaf == null)
{
throw new ArgumentNullException("leaf");
}
Node ll = null;
if (leaf.Boxes.Count == maximumSize)
{ // split the node.
// add the child.
leaf.Boxes.Add(box);
leaf.Children.Add(item);
Node[] split = RTreeMemoryIndex <T> .SplitNode(leaf, minimumSize);
leaf.Boxes = split[0].Boxes;
leaf.Children = split[0].Children;
RTreeMemoryIndex <T> .SetParents(leaf);
ll = split[1];
}
else
{
// add the child.
leaf.Boxes.Add(box);
leaf.Children.Add(item);
}
// adjust the tree.
Node n = leaf;
Node nn = ll;
while (n.Parent != null)
{ // keep going until the root is reached.
Node p = n.Parent;
RTreeMemoryIndex <T> .TightenFor(p, n); // tighten the parent box around n.
if (nn != null)
{ // propagate split if needed.
if (p.Boxes.Count == maximumSize)
{ // parent needs to be split.
p.Boxes.Add(nn.GetBox());
p.Children.Add(nn);
Node[] split = RTreeMemoryIndex <T> .SplitNode(
p, minimumSize);
p.Boxes = split[0].Boxes;
p.Children = split[0].Children;
RTreeMemoryIndex <T> .SetParents(p);
nn = split[1];
}
else
{ // add the other 'split' node.
p.Boxes.Add(nn.GetBox());
p.Children.Add(nn);
nn.Parent = p;
nn = null;
}
}
n = p;
}
if (nn != null)
{ // create a new root node and
var root = new Node();
root.Boxes = new List <BoxF2D>();
root.Boxes.Add(n.GetBox());
root.Boxes.Add(nn.GetBox());
root.Children = new List <Node>();
root.Children.Add(n);
n.Parent = root;
root.Children.Add(nn);
nn.Parent = root;
return(root);
}
return(null); // no new root node needed.
}
