Build bounding volumes for all Bsp nodes. The bounding volume of the node completely encloses the "outside" space occupied by the nodes. Note that this is not the same as representing the bounding volume of all of the polygons within the node. We start with a practically-infinite cube and filter it down the Bsp, whittling it away until all of its convex volume fragments land in leaves.
source not stored for this graph (policy: none)