/// <summary>
/// Creates a <see cref="QuadTree{T}"/> with a boundary defined by the specified <see cref="IQTBoundary"/>.
/// </summary>
/// <param name="boundary">Bounding area.</param>
public QuadTree(IQTBoundary boundary)
{
rootTree = new QuadTreeNode <T>(boundary);
itemDictionary = new Dictionary <T, XY>(new ObjectReferenceEqualityComparer <T>());
}