In the previous and familiar
plane each Z trajectory can wander over the entire image plane. When we
project onto a major plane involving one of the C axies, each point in
each Z trajectory will appear to wander only along a single image row
column as determined by the particular random initial C. This is most
imagined by thinking of the above image as being a "side-to-side view"
through a 3D box who's front-to-back view gave the previous image. Of
the box is really four dimensional but the analogy is accurate.