Bucket PR Quadtree Demo
Recursively decompose the underlying space into four equal area
blocks until the number of data points in each block does not exceed the
bucket capacity. The partition positions are independent of the
details, see pages 45-47 of Samet,
Foundations of Multidimensional and Metric Data Structures
or, see pages 100-101 of Samet, Design and
Analysis of Spatial Data Structures.