1) A subject (car, horse, person, etc.) can cross the line establishing a new one by the direction of his new line of motion. 2) The camera can cross the line either following a subject to a new scene space or merely traveling for graphic variety to a new viewpoint. 3) A new subject can enter the frame and become the dominant line of motion in contrast to the first. This is analogous to the situation in Figure 6.13 when a new character entered the scene establishing a new line of sight.
