Beyond the Looking Glass : The Haptic Exploration of Virtual Environments

The visual quality, complexity and fidelity of virtual environments displayable on modern computer systems continues to grow unabated. A barrier exists, however, between these worlds and our own, leaving them presently out of reach. This thesis examines two technologies, haptic rendering and dynamic simulation, that help to break the barriers between these worlds by allowing direct “hands-on” interaction with physically intuitive virtual environments. Haptic systems allow users to receive and transmit information by touch. Through a force-reflecting mechanical device, users experience the illusion of contact with a real body. A novel representative model is created to allow the robust display of an object given its geometry and surface characteristics. This model attempts to, whenever possible, take advantage of representations that are common in graphics display, including geometry, shading and texture. The algorithms which comprise this model enable realistic contact with arbitrarily complex virtual objects. The advantage of being able to touch virtual objects would be of limited value, however, if the objects did not react in a physically intuitive manner. Objects cannot be described solely in terms of their geometric properties; they must also mimic physical characteristics such as mass, inertia and non-penetration. In the second part of the thesis a framework to efficiently resolve collision and contact constraints between different complex multi-body articulated systems is developed. This framework simplifies the resulting equations by breaking the space of motions between components effected by the collision and those that do not. The models developed for this framework also highlight many of the attributes common to simulation, robotic control and dynamic modeling. This thesis presents results incorporating both haptics and dynamic simulation for tasks in a variety of disciplines. Whether for training; research, education or entertainment, the technologies described help add tangible value to the virtual experience.