A Hybrid Approach for a Real-time Haptic and Graphic Simulator in Virtual Environment

In interacting with a soft object, both visual and haptic senses play major role in providing the characteristics of the object. While visual feedback comes from the appearance of the overall shape, haptic feedback comes largely from the localized internal composition. However, it has been a common practice to represent the object with one model for both processing shape de formation and computing the feedback force, making it much challenging work to achieve real-time simulation of a soft and especially non-homogeneous object. In this paper, we claim that it may be sufficient to represent the graphical visual model as a surface model whereas it is necessary to represent the haptic model as a volumetric model. We propose, therefore, a hybrid model where volumetric haptic model and surface graphical model coexist. For constructing hybrid model, we employ S-chain model to compute the haptic behavior and mass-spring model to calculate graphic behavior. We conduct experiments with volumetric human liver model at a haptic update rate of 1000 Hz and graphic update rate of 30 Hz. The experimental results show that our proposed model satisfies the real-time performance and provides the realistic sense to be useful for a virtual reality application.