High Fidelity Haptic Rendering (Synthesis Lectures in Computer Graphics and Animation)
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The human haptic system, among all senses, provides unique and bidirectional communication between humans and their physical environment. Yet, to date, most human-computer interactive systems have focused primarily on the graphical rendering of visual information and, to a lesser extent, on the display of auditory information. Extending the frontier of visual computing, haptic interfaces, or force feedback devices, have the potential to increase the quality of human-computer interaction by accommodating the sense of touch. They provide an attractive augmentation to visual display and enhance the level of understanding of complex data sets. They have been effectively used for a number of applications including molecular docking, manipulation of nano-materials, surgical training, virtual prototyping, and digital sculpting. Compared with visual and auditory display, haptic rendering has extremely demanding computational requirements. In order to maintain a stable system while displaying smooth and realistic forces and torques, high haptic update rates in the range of 5001000 Hz or more are typically used. Haptics present many new challenges to researchers and developers in computer graphics and interactive techniques. Some of the critical issues include the development of novel data structures to encode shape and material properties, as well as new techniques for geometry processing, data analysis, physical modeling, and haptic visualization. This synthesis examines some of the latest developments on haptic rendering, while looking forward to exciting future research in this area. It presents novel haptic rendering algorithms that take advantage of the human haptic sensory modality. Specifically it discusses different rendering techniques for various geometric representations (e.g. point-based, polygonal, multiresolution, distance fields, etc), as well as textured surfaces. It also shows how psychophysics of touch can provide the foundational design guidelines for developing perceptually driven force models and concludes with possible applications and issues to consider in future algorithmic design, validating rendering techniques, and evaluating haptic interfaces.
Glencross et al. [GHL05] have proposed a caching technique for haptic rendering of up to hundreds of thousands of distinct objects in the same scene. Their haptic cache maintains only objects in the locality of the haptic probe. 1.5.3 Three-DoF Versus Six-DoF Haptic Rendering As mentioned earlier, 3-DoF haptic display is adequate for applications where the interaction between the subject and the virtual objects is sufficiently captured by a point–surface contact model. However, for 6-DoF
linear-time performance in practice. Cameron [Cam97] modified the GJK algorithm to exploit motion coherence in the initialization of the convex optimization at every frame for dynamic problems, achieving nearly constant running-time in practice. Lin and Canny [LC91, Lin93] designed the Voronoi marching algorithm for computing separation distance by tracking the closest features between convex polyhedra. The motivation behind the algorithm is to partition the space into cells such that all points
P1: OTE/PGN MOBK043-03 P2: OTE/PGN QC: OTE/PGN MOBK043-Otaduy.cls T1: OTE October 17, 2006 16:53 COLLISION DETECTION METHODS 63 FIGURE 3.18: CLODs on the BVTT. Left: BVTT in which levels are sorted according to increasing CLOD resolution. Right: the front of the BVTT for an exact contact query, F, is raised up to the new front F using CLODs ( c ACM, 2003). tolerance dab for the contact query between BVs a and b may be computed as dab = d + h(a) + h(b), (3.5) where h(a) and h(b) are
moves exactly along the surface. This connection between penetration depth and offset surfaces can be generalized to nonspherical probes through the concept of Minkowski sum. An offset surface corresponds to the boundary of the Minkowski sum of a given surface and a sphere. Therefore, the height of the offset surface at a particular point is the distance to the boundary of the Minkowski sum for a particular position of the probe, which is the same as the penetration depth. Actually, the height of
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