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UBC Theses and Dissertations

All the distant horizon edges of a terrain Archambault, Daniel

Abstract

Terrains used in Geographic Information Systems (GIS) in some applications require a large number of points to express a fine level of detail over a large area. At distant viewpoints, this fine level of detail is often not visually important. It therefore makes sense to coarsen the level of detail in order to reduce rendering costs. There is some evidence that if models are constrained to preserve silhouettes, then coarser meshes can be used with little loss in visual quality. The purpose of this thesis is to describe an algorithm that determines the set of edges of a polyhedral terrain that lie on some horizon for some distant view of the model. The algorithm computes this by maintaining the two-dimensional visual hull developed by Laurentini [30] of the intersection of the terrain with a horizontal plane sweeping from highest to lowest altitude. Changes in the structure of the visual hull delimit changes in the horizon. All such changes can be detected by using tools developed for kinetic visibility.

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