Haptic Interaction with Deformable Objects: Modelling VR Systems for Textiles (Springer Series on Touch and Haptic Systems)
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The focus from most Virtual Reality (VR) systems lies mainly on the visual immersion of the user. But the emphasis only on the visual perception is insufficient for some applications as the user is limited in his interactions within the VR. Therefore the textbook presents the principles and theoretical background to develop a VR system that is able to create a link between physical simulations and haptic rendering which requires update rates of 1\, kHz for the force feedback. Special attention is given to the modeling and computation of contact forces in a two-finger grasp of textiles. Addressing further the perception of small scale surface properties like roughness, novel algorithms are presented that are not only able to consider the highly dynamic behaviour of textiles but also capable of computing the small forces needed for the tactile rendering at the contact point. Final analysis of the entire VR system is being made showing the problems and the solutions found in the work
behaviour are described in the impulse response of the material (in stresses) with respect to a strain unit pulse. A history of strains is required to perform the frequency decomposition of the strain signal yielding the temporal stress response. Therefore, proper modelling demands a considerable amount of computation time and storage which makes a precise model not yet suitable for real-time simulation. The interested reader might look into  for a comprehensive view. Nevertheless, ignoring
change limits the input to periodic sequences. A sequence of N values of samples in time domain corresponds to N values in the frequency domain. By replacing the integration with a summation, the new scalar product N −1 f, g := f (k)g(k) (3.13) k=0 and the new basis k bω (k) := eiω N with ω = 2πm, m = 1 − N/2 (3.14) reflect those changes. Since the new formula considers only discrete frequency components of the signal, the transformation method is called Discrete Fourier Transform (DFT).
VR system creating the touch perception is also often referred to as haptic rendering. The term is related to the graphical rendering which provides visual information by rendering a scenery pixel by pixel. Despite the similarity of the haptic rendering in providing a sensory image, it differs significantly in its computation. The rendering of graphical images and thus the estimation of a pixel colours is a local problem independent from pixel to pixel whereas the haptic rendering needs to
latter approach is the treatment of the triangles within their local frame of reference. To illustrate the working principle of the algorithm see Fig. 3.29 as an example. At start, the algorithms tries to reject non-intersecting triangles. For doing this, it first uses the plane equation of triangle B to compute the relative distances d0 , d1 , d2 of the points of triangle A. These distances determine the location of triangle A with respect to the plane of B. If the di ’s have the same sign and
By the treatment of the contact in different states, new contact resolution methods were defined according to the current state. The proper tracking of the contact state not only enabled a stable contact but also the concurrent generation of tactile information of the touch used to create tactile stimuli. While the methods implemented here are promising, especially considering the successful reconstruction of subjective evaluation procedures, some of the methods are highly specialised to the