Movements and Gestures

We start by considering a classification of movement tracking systems according to the placement between source and sensor, proposed by A. Mulder [6]. Considering that a movement is always relative to a reference, a sensor on the body can monitor a source attached to a reference, both can be attached to the body or finally the sensor is attached to a reference and the source is placed on the body.

Mulder thus classifies movement tracking systems as:

• "inside-in", when both the sensor and the source are on the body - useful for measuring different movements, but usually obtrusive. No 3D information available. Examples : Hall effect devices, potentiometers (angular rotation sensor!!!), bodysynth, etc.
• "inside-out", when the sensor is placed on the body and the source (natural or artificial) to the external reference. Tracks bigger body parts and usually are more accurate than inside-in systems. Can track 3D info and are usually less obtrusive. Ex. accelerometers.
• "outside-in", when the sensor is attached to an external reference and the source is place on the body (or is the body or part of it). Usually the least obtrusive but the most complex, such as eye-tracking systems, movement tracking using video cameras (BigEye), etc.

We consider here a body gesture as a special kind of body movement, mostly hands, lips or feet movement. We could say that a gesture is a specific movement from part of the body, executed or not in a conscious way, applied or not to a device, that can accompany a discourse or have a meaning by itself. This meaning can be universal or cultural dependent (idiosyncratic). (or as Mulder states: "hand posture and gesture describe situations where hands are used as a means to communicate to either machine or human" [7]).

Another consideration is the differentiation between gesture and posture, where the first has a dynamic nature and the last a static one. In this way, hand gestures are hands and/or finger (and arms) movements. Hand posture is a specific static position of the hand and finger at a particular moment 2.

NB: From this point on, we are going to consider mostly hand gestures and their functions.
 

• Gestural channel and the function of gesture

Wed Feb 10 10:07:20 MET 1999