A simple 2D example of the Pharmer KDB-tree. (a) The area surrounding the point set is divided with cutting planes (solid lines) and bounding boxes (dashed lines) to form (b) a search tree. Because of the explicit bounding boxes, a range query around q (white point), despite intersecting several cutting planes, only need traverse a single branch of the tree, shown as thick-lined nodes in (b), and the search terminates early when it is determined that the points of node c-d are completely contained within the query range.