/// <summary>
/// A manager for a quadtree data structure.
/// </summary>
/// <param name="x">The x position of the top-left corner of the root node bounding box.</param>
/// <param name="y">The y position of the top-left corner of the root node bounding box.</param>
/// <param name="width">The width of the root node bounding box.</param>
/// <param name="height">The height of the root node bounding box.</param>
public GenQuadtree(float x, float y, float width, float height)
{
MaxObjects = 5;
MaxLevels = 5;
_rootNode = new GenQuadtreeNode(x, y, width, height, this, null, 0);
Objects = new List<GenObject>();
_activeObjects = new List<GenObject>();
_updateObjects = false;
_objectLocations = new Dictionary<GenObject, GenQuadtreeNode>();
}
/// <summary>
/// A single node within a quadtree data structure.
/// Used as a container for objects or other nodes.
/// </summary>
/// <param name="x">The x position of the top-left corner of the node bounding box.</param>
/// <param name="y">The y position of the top-left corner of the node bounding box.</param>
/// <param name="width">The width of the node bounding box.</param>
/// <param name="height">The height of the node bounding box.</param>
/// <param name="quadtree">A reference to the quadtree manager of this node.</param>
/// <param name="parentNode">The quadtree node that this node is a leaf of. Use null if this is a root node.</param>
/// <param name="level">The split level of the node.</param>
public GenQuadtreeNode(float x, float y, float width, float height, GenQuadtree quadtree, GenQuadtreeNode parentNode, int level)
: base(x, y, width, height)
{
_quadtree = quadtree;
_parentNode = parentNode;
_level = level;
_objects = new List<GenObject>();
_objectCount = 0;
_nodes = new GenQuadtreeNode[4];
}
internal void Add(GenObject gameObject)
{
if (_nodes[0] == null)
{
Insert(gameObject);
// If the node is full, attempt to add each of its objects into a leaf node.
if ((_objects.Count >= _quadtree.MaxObjects) && (_level < _quadtree.MaxLevels))
{
int nextLevel = _level + 1;
// Create the leaf nodes.
_nodes[0] = new GenQuadtreeNode(_minX, _minY, _halfWidth, _halfHeight, _quadtree, this, nextLevel);
_nodes[1] = new GenQuadtreeNode(_midpointX, _minY, _halfWidth, _halfHeight, _quadtree, this, nextLevel);
_nodes[2] = new GenQuadtreeNode(_minX, _midpointY, _halfWidth, _halfHeight, _quadtree, this, nextLevel);
_nodes[3] = new GenQuadtreeNode(_midpointX, _midpointY, _halfWidth, _halfHeight, _quadtree, this, nextLevel);
// Iterate through the objects list in reverse, attempting to add each object into a leaf node.
// Otherwise, leave the object in this node.
for (int i = _objects.Count - 1; i >= 0; i--)
{
int index = GetIndex(_objects[i].MoveBounds);
if (index != -1)
{
_nodes[index].Add(_objects[i]);
_objects.Remove(_objects[i]);
}
}
}
}
else
{
// Since leaf nodes have already been created, attempt to add the object into a leaf node.
// Otherwise, add the object to this node.
int index = GetIndex(gameObject.MoveBounds);
if (index != -1)
_nodes[index].Add(gameObject);
else
Insert(gameObject);
}
_objectCount++;
}
/// <summary>
/// Decrements the object cound in a given node.
/// Clears each leaf node within the given node if the object count is 0.
/// Walks up the tree from the first given node, repeating the process for each parent node.
/// </summary>
/// <param name="node">The node to check for its object count.</param>
protected void CheckObjects(GenQuadtreeNode node)
{
if (node != null)
{
if (--node._objectCount <= 0)
node.ClearLeaves();
CheckObjects(node._parentNode);
}
}
