Animating indirect manipulation in direct-manipulation editors

If judiciously applied, the techniques of cartoon animation can enhance the illusion of direct manipulation that many human computer interfaces strive to present. Previously, we have shown how animation helps convey a feeling of substance in the objects a user manipulates directly; this paper extends that work to indirect manipulation operations in a drawing editor-those operations initiated by command menus and buttons. Our editor uses two basic techniques: we animate changes in object geometry and graphical attributes to smooth the visual impact of the change, and we use cartooning principles to suggest what effect a geometry-changing operation will have on an object before the operation is committed. Our animations use low-level toolkit support for drawing animated views and managing time-varying data. The prototype editor demonstrates how interface developers can use such support to extend their repertoire of interaction techniques.