15.7 Culling Objects by Planes 711
it is outside the frustum and, therefore, not visible. In this case, the subtree rooted at
the node does not need to be traversed during the drawing pass.
Object culling may be viewed as a test-intersection query, with the minor mod-
ification that if the bounding volume does not intersect a culling plane, we want to
know which side of the plane it is on. This section discusses algorithms for culling
of planar components and various bounding volumes. All such components and
bounding volumes are assumed to be convex.
In all cases, the strategy is simply to project the objects onto a normal line to the
plane and determine if the projection set intersects the plane, lies completely on one
side of the plane, or lies c