of the six plttnes that define the view volume. Lines remaining after clipping would be
projected onto the view plane. by solution of simultaneous equations for the intersection of
the projectors with the view plane. The coordinates would then be transfomied from 3D
world coordinates to 2D device coordinates. However. the large number of calculations
required for this process. repeated for many lines, involves considerable computing.
Happily. there is a more efficient procedure. based on the divide-and~conquel' strategy of
breaking down 21 diflieult problem into a series of simpler ones.
Certain view volumes are easier to clip against than is the general one {clipping
algorithms are discussed in Section 6.5.3). For instance. it is simple to calculate the
intersections of a line with each of the planes of a parallel-projection view volume defined
by the six planes