On the compression and rendering of event-triggered force transients in networked virtual environments

When haptically interacting with virtual rigid bodies, the rendering and display of realistic haptic force-feedback is a challenging task. Conventionally rendered closed-loop proportional feedback forces according to Hooke's law or potential fields impart a feeling of soft contacts and hence are not sufficient to convey the material contact properties of a rigid object. Improvement of haptic contact rendering by incorporating high-frequency transients immediately after contact leads to high packet rates in networked virtual environments (VEs). In this work, we combine event-triggered contact force transients with perceptual coding of haptic signals to achieve a two-fold objective. A significant reduction in data and packet-rates on the network is obtained while improving the realism of interaction with rigid objects, verified by our psychophysical experiments. Furthermore, we describe our observation that the introduction of contact transients serves to mask the artifacts of the perceptual coding scheme to some extent. This allows us to push the data reduction performance beyond what is normally achievable by the haptic compression scheme alone.