Haptic interaction in a virtual world can be tool mediated or direct; and, among direct interactions, the encountered haptic interfaces provide physical contact only when there is contact with a virtual object. This paper deals with the haptic rendering of the catching and throwing of objects by means of this type of interface. A general model for the rendering of the impact is discussed with the associated formalism for managing multiple objects and multiple devices. Next, a key parameter for simulating the impact is selected by means of a psychophysical test. Finally, a working system is presented with the application of the rendering strategy to the case of haptic juggling, showing the possibility of effectively performing basic juggling patterns with two balls.

The use of virtual environments (VE) for training sports is quite natural when considering strategic or cognitive aspects. Using VE for sensorimotor training is more challenging, in particular with the difficulty of transferring the task learned in the virtual world to the real. Of special concern for the successful transfer is the adequate combination of training experience protocols and the delivery modes of multimodal feedback. Analyzing feedback in terms of information exchange, this work discusses different feedback combinations and their application to virtual reality training of rowing skills.