The newest three-dimensional input devices, together with high speed graphics workstations, make it possible to interactively specify virtual camera motions for animation in real time. In this paper, we describe how naturalistic interaction and realistic-looking motion can be achieved by using a physically-based model of the camera's behavior. Our approach is to create an abstract physical model of the camera, using the laws of classical mechanics, which is used to simulate the virtual camera motion in real time in response to force data from the various 3D input devices (e.g. the Spaceball, Polhemus and DataGlove). The behavior of the model is determined by several physical parameters such as mass, moment of inertia, and various friction coefficients which can all be varied interactively, and by constraints on the camera's degrees of freedom which can be simulated by setting certain friction parameters to very high values. This allows us to explore a continuous range of physically-based metaphors for controlling the camera motion. We present the results of experiments with several of these metaphors and contrast them with existing ones.
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