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The NASA Ames Virtual Planetary Exploration (VPE) Testbed is developing methods for visualizing large planetary terrains in an interactive, immersive virtual environment system using a head-mounted display. Our data is the surface of Mars, modeled with a polygon mesh that typically contains 105 or more polygons. The goal of our work is to present terrain views with both high detail and frame update rates of 10 Hz or greater. We do this with extended level of detail (LOD) management. In VPE we include three LOD criteria: (1) distance from the viewpoint, (2) distance from the center of field of view, and (3) a metric based upon user-defined regions of interest. Motivations for these are: (1) all objects, independent of position, only need be displayed at a minimum visually perceptible resolution, (2) interest is focussed on the center of the field in a head-directed display, and (3) a feature's level of detail should relate to its importance to the application task. Our method uses analysis functions for each criterion that compute normalized scale factors. Factors are combined with user specified weights. At every frame update each region of the scene is analyzed, and its resulting scale factor determines which model to render. Parameters for each criterion may be interactively set by the user or automatically set by system to meet performance criteria (e.g., frame update rate).
Hitchner et al. (Wed,) studied this question.