This paper presents evidence that situational awareness in a visualization of data benefits from immersive, virtual reality display technology because such displays appear to support better understanding of the visual information. Our study was designed to deemphasize perceptual and interaction characteristics of the displays and found that the task of counting targets is strongly influenced by the type of system used to render the visualization. Immersive-type displays outperformed traditional monitors. The target objects in the study have distinguishing features that cannot be identified from a distance to alleviate the effect of perceptual differences among displays. Counting was chosen because it entails basic understanding of the relationship among the data values in order to recognize previously counted items. The display choices consisted of a traditional monitor and three configurations of an immersive, projection environment, obtained by selectively turning off one or two projectors of a three-wall CAVE.
Navigation in complex and large-scale 3D virtual environments has been shown to be a difficult task, imposing a high cognitive load on the user. In this paper, we present a comprehensive method for assisting users in exploring and understanding such 3D worlds. The method consists of two distinct phases: an off-line computation step deriving a grand tour using the world geometry and any semantic target information as input, and an on-line interactive navigation step providing guided exploration and improved spatial perception for the user. The former phase is based on a voxelized version of the geometrical dataset that is used to compute a connectivity graph for use in a TSP-like formulation of the problem. The latter phase takes the output tour from the off-line step as input for guiding 3D navigation through the environment.
We present an empirical usability experiment studying the relative strengths and weaknesses of three different occlusion reduction techniques for discovering and accessing objects in information-rich 3D virtual environments. More specifically, the study compares standard 3D navigation, generalized fisheye techniques using object scaling and transparency, and the BalloonProbe interactive 3D space distortion technique. Subjects are asked to complete a number of different tasks, including counting, pattern recognition, and object relation, in different kinds of environments with various properties. The environments include a free-space abstract 3D environment and a virtual 3D walkthrough application for a simple building floor. The study involved 16 subjects and was conducted in a three-sided CAVE environment. Our results confirm the general guideline that each task calls for a specialized interaction-no single technique performed best across all tasks and worlds. The results also indicate a clear trade-off between speed and accuracy; simple navigation was the fastest but also most error-prone technique, whereas spherical BalloonProbe proved the most accurate but required longer completion time, making it suitable for applications where mistakes incur a high cost.
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