Override to handle the intersection with the search space.
To include this node and all nodes below, return INSIDE.
To exclude this node and all nodes below, return OUTSIDE.
To search deeper but perform further intersection tests, return PARTIAL.
A guarantee is made that if this method only returns PARTIAL, every single
table tree node except for the root node shall be handled exactly once.
Methods such as OctreeIterator.getX() and OctreeIterator.getNode() provide information
about what is being tested right now.