Physics Initialization - Learning Game Physics with Bullet Physics and OpenGL - page 41

It is a relatively cheap task to check if two AABBs overlap, but we can still overburden
ourselves if we don't perform some additional optimization. By organizing the objects
by pairs in a tree structure, we naturally organize our objects by distance from one
another, thus automatically culling away the object pairs which are too far apart to be
worth checking, as we can see here:
It takes some processing work to maintain the tree hierarchy as objects move
around, since the AABBs have to be dynamically altered on occasion. But, this is