Simulation-based in-between creation for CACAni system

In-between creation in traditional cel animation based on the hand-drawn key-frames is a fundamental element for the actual production and plays a symbolic role in an artistic interpretation of the scene. To create impressive in-betweens, however, animators are required to be skilled for hair animation creation. In the traditional cel animation, hair motions are generally used to express a character's affective change or showing environment condition. Despite this usability and importance, the hair motion is drawn relatively simply or is not animated at all because of the lack of skilled animators and time constraints in cel animation production. To assist this production process, P. Noble and W. Tang [Noble and Tang. 2004], and Sugisaki et al. [Sugisaki et al. 2006] introduced certain ways to create hair motion for cartoon animations. Both of them created the hair motion based on 3D simulation that is applied to the prepared 3D character model. In this paper, we introduce an in-between creation method, specialized for hair based on dynamic simulation, which does not need any 3D character model. Animators can create in-between frames for hair motion by setting a few parameters, and then our method automatically select the best in-between frames based on the specified frame number by animator. The advantage of our method is to create in-between frames for hair motion by applying simulation model to key-frames. Obviously, the key-frame images do not have any depth. In fact, our method can directly utilize the hand-drawn key-frames which are drawn by animators in CACAni (Computer-Assisted Cel Animation) system [CACAni Website].