/// <summary>
/// Finds the nearest rectangles to the passed point. If multiple rectangles are equally near, they will all be returned.
/// </summary>
/// <param name="p">the point we are looking for</param>
/// <param name="furthestDistance">The furthest distance away from the rectangle to search. Rectangles further than this will not be found.</param>
/// <returns>a PriorityQue containing the found recatngles and their priorities (distances from point)</returns>
public PriorityQueueRTree Nearest(Point p, double furthestDistance)
{
PriorityQueueRTree distanceQueue = new PriorityQueueRTree();
double furthestDistanceSq = furthestDistance * furthestDistance;
rootNode.Nearest(p, this, furthestDistanceSq, distanceQueue);
return(distanceQueue);
}
internal override double Nearest(Point p, RTree rTree, double furthestDistanceSq, PriorityQueueRTree nearestRectangles)
{
for (int i = 0; i < entryCount; i++)
{
double tempDistanceSq = entries[i].Value.distanceSq(p.x, p.y);
if (tempDistanceSq < furthestDistanceSq)
{
furthestDistanceSq = tempDistanceSq;
nearestRectangles.Clear();
}
if (tempDistanceSq <= furthestDistanceSq)
{
nearestRectangles.Insert(entries[i].Value, tempDistanceSq);
}
}
return(furthestDistanceSq);
}
internal override double Nearest(Point p, RTree rTree, double furthestDistanceSq, PriorityQueueRTree nearestRectangles)
{
for (int i = 0; i < entryCount; i++)
{
double tempDistanceSq = entries[i].Value.distanceSq(p.x, p.y);
// a rectangle nearer than actualNearest
if (tempDistanceSq <= furthestDistanceSq)
{
NodeBase node = childNodes[i]; // search the child node
furthestDistanceSq = node.Nearest(p, rTree, furthestDistanceSq, nearestRectangles);
}
}
return(furthestDistanceSq);
}
private PriorityQueueRTree createNearestNDistanceQueue(Point p, UInt32 count, double furthestDistance)
{
PriorityQueueRTree distanceQueue = new PriorityQueueRTree();
// return immediately if given an invalid "count" parameter
if (count == 0)
{
return(distanceQueue);
}
parents.Clear();
parents.Push(rootNode);
parentsEntry.Clear();
parentsEntry.Push(-1);
// TODO: possible shortcut here - could test for intersection with the MBR of the root node. If no intersection, return immediately.
double furthestDistanceSq = furthestDistance * furthestDistance;
while (parents.Count > 0)
{
NodeBase n = parents.Peek();
int startIndex = parentsEntry.Peek() + 1;
if (!n.IsLeaf)
{
// go through every entry in the index node to check if it could contain an entry closer than the farthest entry currently stored.
bool near = false;
NodeInternal nodeInternal = n as NodeInternal;
for (int i = startIndex; i < n.entryCount; i++)
{
if (n.entries[i].Value.distanceSq(p.x, p.y) <= furthestDistanceSq)
{
parents.Push(nodeInternal.childNodes[i]);
parentsEntry.Pop();
parentsEntry.Push(i); // this becomes the start index when the child has been searched
parentsEntry.Push(-1);
near = true;
break; // ie go to next iteration of while()
}
}
if (near)
{
continue;
}
}
else
{
// go through every entry in the leaf to check if it is currently one of the nearest N entries.
for (int i = 0; i < n.entryCount; i++)
{
double entryDistanceSq = n.entries[i].Value.distanceSq(p.x, p.y);
if (entryDistanceSq <= furthestDistanceSq)
{
distanceQueue.Insert(n.entries[i].Value, entryDistanceSq);
while (distanceQueue.Count > count)
{
// normal case - we can simply remove the lowest priority (highest distance) entry
Rectangle value = distanceQueue.ValuePeek;
double distanceSq = distanceQueue.PriorityPeek;
distanceQueue.Pop();
// rare case - multiple items of the same priority (distance)
if (distanceSq == distanceQueue.PriorityPeek)
{
savedValues.Add(value);
savedPriority = distanceSq;
}
else
{
savedValues.Clear();
}
}
// if the saved values have the same distance as the next one in the tree, add them back in.
if (savedValues.Count > 0 && savedPriority == distanceQueue.PriorityPeek)
{
for (int svi = 0; svi < savedValues.Count; svi++)
{
distanceQueue.Insert(savedValues[svi], savedPriority);
}
savedValues.Clear();
}
// narrow the search, if we have already found N items
if (distanceQueue.PriorityPeek < furthestDistanceSq && distanceQueue.Count >= count)
{
furthestDistanceSq = distanceQueue.PriorityPeek;
}
}
}
}
parents.Pop();
parentsEntry.Pop();
}
return(distanceQueue);
}
internal abstract double Nearest(Point p, RTree rTree, double furthestDistanceSq, PriorityQueueRTree nearestRectangles);
