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Computer haptics: rendering techniques for force-feedback in virtual environments

Haptic virtual environments (VEs) are computer-generated environments within which human users can touch, feel, and manipulate virtual objects in real time through force or tactile feedback. Integration of force-feedback into VEs with graphical and auditory displays is expected to have many applications in the area of medical training, CAD/CAM, entertainment, graphic arts, and education. The development of force-feedback system for VEs is in the research area of haptics, which can be divided into three sub-categories: human haptics, machine haptics, and computer haptics. Human haptics focuses on the understanding of human hand brain system. Machine haptics focuses on the design and development of force-feedback devices (also called haptic interfaces). Computer haptics focuses on the algorithm and software for the creation of virtual objects and how to efficiently display these objects to the users. The research of this thesis focuses on computer haptics. First, a point-based interaction paradigm called Neighborhood Watch is developed to allow human users to use a point probe to manually explore and manipulate virtual objects. A major feature of Neighborhood Watch is that the computational time is independent of the number of polygons of the virtual objects. Second, another interaction paradigm, called ray-based rendering, which allows human users to use a line probe to interact with virtual objects is also described. The computational time with ray-based rendering is also essentially independent of the number of polygons of the virtual objects. In addition to the two haptic interaction paradigms, various object property display algorithms have also been developed. Using these algorithms, we can add friction and textures to the surfaces of arbitrarily shaped virtual objects and also add compliant and dynamic behavior to the virtual objects. All of the techniques developed for haptic rendering were finally incorporated into a surgical simulator to demonstrate their usefulness.