/// <summary>
/// Query the QuadTree for items that are in the given area
/// </summary>
/// <param name="queryArea"></pasram>
/// <returns></returns>
public IEnumerable <T> Query(MRectangleF queryArea)
{
// this quad contains items that are not entirely contained by
// it's four sub-quads. Iterate through the items in this quad
// to see if they intersect.
foreach (T item in this.Contents)
{
if (queryArea.IntersectsWith(Tree.GetRect(item)))
{
yield return(item);
}
}
foreach (QuadTreeNode <T> node in m_nodes)
{
if (node.IsEmpty)
{
continue;
}
// Case 1: search area completely contained by sub-quad
// if a node completely contains the query area, go down that branch
// and skip the remaining nodes (break this loop)
if (node.Bounds.Contains(queryArea))
{
foreach (T t in node.Query(queryArea))
{
yield return(t);
}
break;
}
// Case 2: Sub-quad completely contained by search area
// if the query area completely contains a sub-quad,
// just add all the contents of that quad and it's children
// to the result set. You need to continue the loop to test
// the other quads
if (queryArea.Contains(node.Bounds))
{
foreach (T t in node.SubTreeContents)
{
yield return(t);
}
continue;
}
// Case 3: search area intersects with sub-quad
// traverse into this quad, continue the loop to search other
// quads
if (node.Bounds.IntersectsWith(queryArea))
{
foreach (T t in node.Query(queryArea))
{
yield return(t);
}
}
}
}
/// <summary>
/// Insert an item to this node
/// </summary>
/// <param name="item"></param>
public void Insert(T item, MRectangleF rect)
{
// if the item is not contained in this quad, there's a problem
if (!m_bounds.Contains(rect))
{
throw new ArgumentException("feature is out of the bounds of this quadtree node");
}
// if the subnodes are null create them. may not be sucessfull: see below
// we may be at the smallest allowed size in which case the subnodes will not be created
//if (m_nodes.Count == 0)
// CreateSubNodes();
if (m_nodes.Count == 0 && this.Contents.Count >= Tree.NodeCapacity)
{
CreateSubNodes();
MoveContentsToSubNodes();
}
if (this.Contents.Count > Tree.NodeCapacity)
{
//this node is full, let's try and store T in a subnode, if it's small enough.
// for each subnode:
// if the node contains the item, add the item to that node and return
// this recurses into the node that is just large enough to fit this item
foreach (QuadTreeNode <T> node in m_nodes)
{
if (node.Bounds.Contains(rect))
{
node.Insert(item, rect);
return;
}
}
}
//add, even if we are over capacity.
this.Contents.Add(item);
}
/// <summary>
/// Construct a quadtree node with the given bounds
/// </summary>
/// <param name="area"></param>
public QuadTreeNode(MRectangleF bounds, QuadTree <T> tree)
{
Tree = tree;
m_bounds = bounds;
}
/// <summary>
///
/// </summary>
/// <param name="rectangle"></param>
public QuadTree(MRectangleF rectangle)
{
m_rectangle = rectangle;
m_root = new QuadTreeNode <T>(m_rectangle, this);
}
/// <summary>
/// Query the QuadTree, returning the items that are in the given area
/// </summary>
/// <param name="area"></param>
/// <returns></returns>
public IEnumerable <T> Query(MRectangleF area)
{
return(m_root.Query(area));
}