/// <summary>
/// Creates a node and either splits the objects recursively into sub-nodes, or stores them at the node depending on the heuristics.
/// Tree is built top->down
/// </summary>
/// <param name="objList">Geometries to index</param>
/// <param name="depth">Current depth of tree</param>
/// <param name="heurdata">Heuristics data</param>
public QuadTree(List<BoxObjects> objList, uint depth, Heuristic heurdata)
{
_Depth = depth;
_box = objList[0].box;
for (int i = 0; i < objList.Count; i++)
_box = _box.Join(objList[i].box);
// test our build heuristic - if passes, make children
if (depth < heurdata.maxdepth && objList.Count > heurdata.mintricnt &&
(objList.Count > heurdata.tartricnt || ErrorMetric(_box) > heurdata.minerror))
{
List<BoxObjects>[] objBuckets = new List<BoxObjects>[2]; // buckets of geometries
objBuckets[0] = new List<BoxObjects>();
objBuckets[1] = new List<BoxObjects>();
uint longaxis = _box.LongestAxis; // longest axis
double geoavg = 0; // geometric average - midpoint of ALL the objects
// go through all bbox and calculate the average of the midpoints
double frac = 1.0f/objList.Count;
for (int i = 0; i < objList.Count; i++)
geoavg += objList[i].box.GetCentroid()[longaxis]*frac;
// bucket bbox based on their midpoint's side of the geo average in the longest axis
for (int i = 0; i < objList.Count; i++)
objBuckets[geoavg > objList[i].box.GetCentroid()[longaxis] ? 1 : 0].Add(objList[i]);
//If objects couldn't be splitted, just store them at the leaf
//TODO: Try splitting on another axis
if (objBuckets[0].Count == 0 || objBuckets[1].Count == 0)
{
_child0 = null;
_child1 = null;
// copy object list
_objList = objList;
}
else
{
// create new children using the buckets
_child0 = new QuadTree(objBuckets[0], depth + 1, heurdata);
_child1 = new QuadTree(objBuckets[1], depth + 1, heurdata);
}
}
else
{
// otherwise the build heuristic failed, this is
// set the first child to null (identifies a leaf)
_child0 = null;
_child1 = null;
// copy object list
_objList = objList;
}
}
/// <summary>
/// Adds a new <see cref="BoxObjects"/> to this node.
/// </summary>
/// <param name="o">The boxed object</param>
/// <param name="h">The child node creation heuristic</param>
public void AddNode(BoxObjects o, Heuristic h)
{
/* -------------------------------------------------------------------- */
/* If there are subnodes, then consider whether this object */
/* will fit in them. */
/* -------------------------------------------------------------------- */
if (_child0 != null && _depth < h.maxdepth)
{
if (_child0.Box.Contains(o.Box.Centre))
_child0.AddNode(o, h);
else if (_child1.Box.Contains(o.Box.Centre))
_child1.AddNode(o, h);
return;
}
/* -------------------------------------------------------------------- */
/* Otherwise, consider creating two subnodes if could fit into */
/* them, and adding to the appropriate subnode. */
/* -------------------------------------------------------------------- */
if( h.maxdepth > _depth && !IsLeaf )
{
Envelope half1, half2;
SplitBoundingBox(Box, out half1, out half2);
if( half1.Contains(o.Box.Centre))
{
_child0 = new QuadTree(half1, _depth + 1);
_child1 = new QuadTree(half2, _depth + 1);
_child0.AddNode(o, h);
return;
}
if(half2.Contains(o.Box.Centre))
{
_child0 = new QuadTree(half1, _depth + 1);
_child1 = new QuadTree(half2, _depth + 1);
_child1.AddNode(o, h);
return;
}
}
/* -------------------------------------------------------------------- */
/* If none of that worked, just add it to this nodes list. */
/* -------------------------------------------------------------------- */
//Debug.Assert(_child0 == null);
if (_objList == null)
_objList = new List<BoxObjects>();
Box.ExpandToInclude(o.Box);
_objList.Add(o);
}
