Haptic rendering of volumetric soft-bodied objects



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Texas Tech University


The interfacing of force-feedback devices to computers adds touchability in computer interactions, called computer haptics. Computer haptics has two components (1) collision detection of virtual objects with the haptic interface device and (2) determining and displaying appropriate force feedback to the user via the haptic interface device. This is a new field, with most of the original work done in the fields of mechanical engineering and the biophysical sciences. As such, the computing model that incorporates haptics was, until recently, a secondary concern.

Most of the data structures and algorithms applied to haptic rendering have been adopted from non-pliable surface-based graphic systems, which is not always appropriate because of the different characteristics required to render haptic systems. Two new algorithms are currently available that can be applied to haptics to improve the collision detection and force-feedback generation of computer haptics. Currently, there are two basic methods available: (1) The occupancy-map algorithm (OMA), which is used for fast collision detection with solid non-deformable convex virtual objects, (2) The chainmail algorithm (CMA) used for calculating the behavior of 2D (surface) convex objects.

The work we have done uses advanced computer modeling and coding techniques or implementing 1) haptic rendering of 3D volumetric objects using OMA for collision detection and 2) CMA for the generation of the real-time force feedback. Comparative analysis of this technique for haptic rendering versus more traditional methods has been provided. This work has enhanced the previous versions of this technique and has shown the viability and advantages of this new haptic rendering paradigm. These algorithms were implemented using the PHANToM haptic device from Sensible Technologies. This is a six-degree of freedom force feedback device used with many haptic displays. Graphics were implemented using the version of OpenGL provided with the Windows NT operating system.