In a virtual environment for small groups of interacting participants, it is important that the physical motion of each participant be replicated by synthetic human forms in real time. Sensors on a user's body are used to drive an inverse kinematics algorithm. Such iterative algorithms for solving the general inverse kinematics problem are too slow for a real-time interactive environment. In this paper we present analytic, constanttime methods to solve the inverse kinematics problem and drive an avatar figure. Our sensor configuration has only eight sensors per participant, so the sensor data is augmented with information about natural body postures. The algorithm is fast, and the resulting avatar motion approximates the actions of the participant quite well. This new analytic solution resolves a problem with an earlier iterative algorithm that had a tendency to position knees and elbows of the avatar in awkward and unnatural positions.
We have implemented a browser companion called PadPrints that dynamically builds a graphical history-map of visited web pages. PadPrints relies on Pad++, a zooming user interface (ZUI) development substrate, to display the history-map using minimal screen space. PadPrints functions in conjunction with a traditional web browser but without requiring any browser modifications.We performed two usability studies of PadPrints. The first addressed general navigation effectiveness. The second focused on history-related aspects of navigation. In tasks requiring returns to prior pages, users of PadPrints completed tasks in 61.2% of the time required by users of the same browser without PadPrints. We also observed significant decreases in the number of pages accessed when using PadPrints. Users found browsing with PadPrints more satisfying than using Netscape alone.
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