Problem
1. Devise an algorithm to clip objects in a scene against a defined frustum. Compare the operations needed in this algorithm to those needed in an algorithm that clips against a regular parallelepiped.
2. Modify the two-dimensional bang-Barsky line-clipping algorithm to clip three-dimensional lines against a specified regular parallelepiped.
3. Modify the two-dimensional Liang-Barsky line-clipping algorithm to clip a given polyhedron against a specified regular parallelepiped.