/// <summary>
/// Prunes the tree by deleting empty leaf nodes
/// </summary>
private void Prune()
{
if (m_Leaf)
{
return;
}
// Can we condense child nodes into this one?
if (m_Count <= NumObjects)
{
if (m_NorthWest != null)
{
m_Objects.AddRange(m_NorthWest); m_NorthWest = null;
}
if (m_NorthEast != null)
{
m_Objects.AddRange(m_NorthEast); m_NorthEast = null;
}
if (m_SouthWest != null)
{
m_Objects.AddRange(m_SouthWest); m_SouthWest = null;
}
if (m_SouthEast != null)
{
m_Objects.AddRange(m_SouthEast); m_SouthEast = null;
}
m_Leaf = true;
return;
}
bool anyChildrenAlive = false;
if (m_NorthWest != null)
{
if (m_NorthWest.m_Count == 0)
{
m_NorthWest = null;
}
else
{
m_NorthWest.Prune();
anyChildrenAlive = true;
}
}
if (m_NorthEast != null)
{
if (m_NorthEast.m_Count == 0)
{
m_NorthEast = null;
}
else
{
m_NorthEast.Prune();
anyChildrenAlive = true;
}
}
if (m_SouthWest != null)
{
if (m_SouthWest.m_Count == 0)
{
m_SouthWest = null;
}
else
{
m_SouthWest.Prune();
anyChildrenAlive = true;
}
}
if (m_SouthEast != null)
{
if (m_SouthEast.m_Count == 0)
{
m_SouthEast = null;
}
else
{
m_SouthEast.Prune();
anyChildrenAlive = true;
}
}
m_Leaf = !anyChildrenAlive;
}
/// <summary>
/// Inserts the given object into the appropriate child node.
/// Assumes the given object is within the trees <see cref="m_Region"/>
/// </summary>
private void InsertIntoChildren(T obj)
{
if (obj.Position.X < m_Region.Left + (m_Region.Width / 2))
{
if (obj.Position.Y < m_Region.Top + (m_Region.Height / 2))
{
if (m_NorthWest == null)
{
m_Leaf = false;
m_NorthWest = new QuadTree <T>(
new FloatRect(m_Region.Left, m_Region.Top,
m_Region.Width / 2, m_Region.Height / 2),
obj);
}
else
{
m_NorthWest.Insert(obj);
}
}
else
{
if (m_SouthWest == null)
{
m_Leaf = false;
m_SouthWest = new QuadTree <T>(
new FloatRect(m_Region.Left, m_Region.Top + m_Region.Height / 2,
m_Region.Width / 2, m_Region.Height / 2),
obj);
}
else
{
m_SouthWest.Insert(obj);
}
}
}
else
{
if (obj.Position.Y < m_Region.Top + (m_Region.Height / 2))
{
if (m_NorthEast == null)
{
m_Leaf = false;
m_NorthEast = new QuadTree <T>(
new FloatRect(m_Region.Left + m_Region.Width / 2, m_Region.Top,
m_Region.Width / 2, m_Region.Height / 2),
obj);
}
else
{
m_NorthEast.Insert(obj);
}
}
else
{
if (m_SouthEast == null)
{
m_Leaf = false;
m_SouthEast = new QuadTree <T>(
new FloatRect(m_Region.Left + m_Region.Width / 2, m_Region.Top + m_Region.Height / 2,
m_Region.Width / 2, m_Region.Height / 2),
obj);
}
else
{
m_SouthEast.Insert(obj);
}
}
}
}
