David Luebke
University of North Carolina at Chapel Hill
Dissertation submitted to the faculty of the University of North Carolina at Chapel Hill
Abstract
This dissertation describes hierarchical dynamic simplification (HDS), a new
approach to the problem of simplifying arbitrary polygonal environments. HDS is
dynamic, retessellating the scene continually as the user’s viewing position shifts, and
global, processing the entire database without first decomposing the environment into
individual objects. The resulting system enables real-time display of very complex
polygonal CAD models consisting of thousands of parts and millions of polygons. HDS
supports various preprocessing algorithms and various run-time criteria, providing a
general framework for dynamic view-dependent simplification.
Briefly, HDS works by clustering vertices together in a hierarchical fashion. The
simplification process continually queries this hierarchy to generate a scene containing
only those polygons that are important from the current viewpoint. When the volume of
space associated with a vertex cluster occupies less than a user-specified amount of the
screen, all vertices within that cluster are collapsed together and degenerate polygons
filtered out. HDS maintains an active list of visible polygons for rendering. Since frameto-
frame movements typically involve small changes in viewpoint, and therefore modify
this list by only a few polygons, the method takes advantage of temporal coherence for
greater speed.
Paper
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