View-Dependent Simplification Of Arbitrary Polygonal Environments

David Luebke, Carl Erikson
Department of Computer Science
University of North Carolina at Chapel Hill

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Abstract

Hierarchical dynamic simplification (HDS) is a new approach to the problem of simplifying arbitrary polygonal environments. HDS operates dynamically, retessellating the scene continuously as the user's viewing position shifts, and adaptively, processing the entire database without first decomposing the environment into individual objects. The resulting system allows real-time display of very complex polygonal CAD models consisting of thousands of parts and hundreds of thousands 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 continuously 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 frame-to-frame movements typically involve small changes in viewpoint, and therefore modify the active list by only a few polygons, the method takes advantage of temporal coherence for greater speed.

Color Plates

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Plate 1: Bone6 model shown at original resolution (1,136,785 faces), 0.5% error tolerance (417,182 faces), and 1% error tolerance (172,499 faces).


Plate 2: Sphere model shown at original resolution (8,192 faces), at 1% error threshold with backface simplification (3,388 faces), and at 1% silhouette error threshold with a 20% interior error tolerance (1,950 faces).


Plate 3: Bunny model shown at original resolution (69,451 faces), 1% error tolerance (19,598 faces), and 5% error tolerance (2,901 faces).


Plate 4: Bunny model shown with 1% silhouette, 6% interior (13,135 faces).

Plate 5: Sierra model shown at original resolution (154,153 faces) and 1.5% error tolerance (54,847 faces).


Plate 6: AMR model shown at original resolution (501,550 faces), 0.7% error tolerance (123,106 faces), and 2.5% error tolerance (34,128 faces).


Plate 7: AMR model shown at the same error tolerances as Plate 6, but drawn with wireframes on.


Plate 8: Torp model shown at original resolution (673,728 faces), 0.8% error tolerance (129,446 faces), and 1.5% error tolerance (76,404 faces).


Plate 9: Torp model shown at the same error tolerances as Plate 8, but drawn with wireframes on.