Sculpting and animating in a desktop VR environment

Precise control of the shape of a flexible object during animation is a time-consuming task for the animator, for which there is, as yet, no universally-applicable method. This paper describes a system which provides improved support in this area. In the system, objects are modelled within a stereoscopic environment, and the user interfaces with the system via two hand-held devices, a SpaceBall and a mouse. The object is positioned and oriented by "holding" it in one hand, while the other hand employs the mouse to sculpt the object as if it were made of clay, using a "point and click" paradigm, rather than the conventional "pick and drag" approach. The object is sculpted at several pre-defined key positions before animation begins-these are defined parametrically, allowing animation of the object by interpolation in a straightforward way. To support this process and to ensure that the shape of the object remains sensible between the key positions, an extension to NURBS, called CISSes, has been developed. As a result of rests of a prototype system, the Basic CISS was further developed into the Cuboid CISS. The coherence of the object under animation can be mathematically demonstrated for the Cuboid CISS. This paper describes the Virtual Sculpting environment, the mathematical background of the CISS, and the results obtained using this approach for the animation of a limb. The final section identifies outstanding problems and future areas of work.