Cover Fieldtree or Loose Quadtree
The cover fieldtree and the equivalent
loose quadtree (loose octree in three dimensions),
is obtained by expanding the size of the space
that is spanned by each quadtree block
c of width w by a block expansion factor p (p>0) so that the
expanded block is of width w.(1+p).
Thus instead of associating (inserting) objects with (into) their
minimum enclosing quadtree blocks as in MX-CIF quadtrees,
they are associated with (inserted
into) their minimum expanded quadtree block.
For more details, see pages 257-259, 466-473 and 827-832 of Samet,
Foundations of Multidimensional and Metric Data Structures
and, see pages 200-213 of Samet, Design and Analysis of Spatial Data Structures.
Instructions
In Insert mode, click and drag to specify a new rectangle. In
Delete mode click inside an existing rectangle to remove it from
the quadtree. If you click in an area that is occupied by several rectangles,
one of them will be chosen arbitrarily and deleted.
In Search mode, click and drag to specify a rectangle. All rectangles
stored in the loose quadtree overlapped by the new rectangle will be drawn
in blue.