[DGD] Using r-trees to subdivide a world

[Shentino]

The big reason why "real" objects and mere r-tree type nodes are
separately managed is:

*drumroll...*

In game logic can change the regions occupied/enclosed by such objects
arbitrarily.

A volcanic eruption may create new landscape, and a treaty between two
adjacent nations could screw with the borders.

For these reasons, I need an object located in a particular *logical*
area to only leave that area on express orders from other logic.

The borders of a city, treasure chest, nation, or galactic sector are
determined by game logic, and that makes them incompatible with piggy
backing on r-tree nodes.

It was otherwise a nice idea, but r-tree structure can't override in
game logic that may well arrange things artificially on purpose.  It
has to yield to it.