• sketch interface;
  • multiple-pass sketching;
  • computer animation


We introduce a multiple-pass sketch-based user interface, designed for novice users, which avoids spatial ambiguities and hence allows considerable freedom in creating 3D animations. The user first draws the path along which a character or object is to move. A vertical motion window is then erected along this path, on which the user specifies the character's gestures or the object's vertical movements. A further cross-motion window can be used to add detail to the movements of the object. Window-specific camera modules present the user with appropriate views, extending the fluidity of pencil and paper to 3D. A usability study involving 60 users, who were previously unfamiliar with 3D animation tools, demonstrated that the proposed interface is easy to learn and effective in use. Copyright © 2010 John Wiley & Sons, Ltd.