Game Development Reference
In-Depth Information
Models for haptic rendering
Philippe Meseure and Abderrahmane Kheddar
The use of haptic interfaces makes it possible to enhance the interaction between the
user and a virtual environment, by developing it on the sense of touch. Such interfaces
can be seen not only in professional applications, but also in consumer applications.
However, controlling these devices from a virtual environment still remains an open
problem. In fact, haptic interfaces do not necessarily come with a programming library
that helps controlling these interfaces in a simple manner. Some libraries available (for
example GHOST by Sensable 1 ) are specific to the devices of a given brand and to
certain virtual environments. They often prove to be unsuitable for applications that
use complex scenarios. Therefore, the VR application designers often have to program
the haptic interfaces that they use. Similar to computer graphics that work on the
synthesis of images that the user has to see (graphic rendering), computer haptics that
we are going to discuss in this chapter, aim at calculating haptic sensations that the
user has to feel (haptic rendering). More specifically, we will see how to calculate the
set point to be sent to the control loop described in chapter 9 “Control of a Force
Feedback Interface'' of this topic. We will also discuss various problems related to the
simulation/device coupling.
16.1 HAPTIC SIMULATION/DEVICE COUPLING
The main objective of a simulation/device coupling is calculating and exactly reproduc-
ing haptic data such as the contact forces in a simulated environment. This restitution
should also be stable and guarantee maximum safety during its use. In most of the
cases, a haptic device makes it possible to control a virtual object, which appears as
a “re-transcription'' or an image of the interface in the simulated environment. This
manipulated object is generally called an avatar or a proxy . The haptic feedback result-
ing from the interactions between the avatar and the virtual environment has various
components; the most important of them are:
Kinaesthetic feedback or force rendering corresponding to the forces and dis-
placements opposite to the movements of any object being manipulated inter-
actively. These forces are felt by the operator mainly at his joints (handle, elbow,
shoulder, etc.);
1 www.sensable.com
 
 
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