As the previous poster has implied, An animatic can evolve directly from a storyboard. The frames of the storyboard are placed directly on a timeline (e.g. premier) and sometimes given a few animations (e.g. zoom, pan etc) and annotations. As the animation progresses, rough 3D renders (sometimes called flip books) can be dropped onto this timeline. In this way, the final movie can evolve directly from the animatic.

What made Flow unusual is that they bypassed the storyboard almost entirely, which is unusual for a feature film. One rational is that the movie features significant and lengthy camera motion shots. Camera motion is very difficult to capture in a storyboard.

At a student level, another motivation for lessening the importance of the storyboard is that they require not insignificant drawing skills in order to do effectively. Even animation students cannot be guaranteed to draw well, and the number of student filmmakers who can draw is vanishingly small.