ABSTRACT
This chapter deals with motor interfaces that are specifically dedicated to the hand. In the real world, grasping an object by hand is a phenomenon that brings into play, even if subconsciously, complex processes at the sensorimotor and cognitive levels. The motor interface that seems to be the most suitable, in theory, is the dataglove which can measure hand and finger movements. A lot of designers have used the dataglove as a tool to handle virtual objects without much thought. Handling is one of the four categories of “Virtual Behavioural Primitives’’ (VBPs), in other words, the problem of selecting the handling interface is common. If we think about this, we observe that it is often a question of being able to easily move in object rotation and translation motion (from 2 to 6 DOF). Effective grasping of the object is often simplistic: the object is either grasped or released. These frequent instances do not require using a dataglove. A simple tracker suffices to indicate the movements of the object, which is gripped and released by a simple binary control. This command can be given by a button or by simply taking a virtual cursor on the screen closer to the object to be handled. We thus benefit from the simplicity of the laws of the virtual world, as compared to the real world. This explains the fact that not many applications really need a dataglove, and that their commercial development is relatively slow. The designer of a virtual reality application should thus always ask himself: is it necessary to use a dataglove? Wouldn’t a tracker suffice?
