To illustrate our approach, consider the simple example of animating
a flying dragon (Fig. 1). Animating the dragon requires the
coordination of its shape over time as to follow the path’s shape.
With our approach, the basic animation can be created with a single
sketched stroke. The stroke is used not only to provide the path of
travel, but also to define how an abstraction of the character’s shape
(its line of action) changes over time. Additional strokes can be
used to refine the movement, or add details such as the flapping of
the wings. Creating such motion with existing approaches would
require coordinating a large number of keyframes that specify deformations
and positions along the path, or a method for puppeteering
the degrees of freedom of the dragon.