authors 
Clark, James H. 
year 
1976 
title 
Hierarchical Geometric Model for Visible Surface Algorithms 
source 
communications of the ACM. October, 1976. vol. 19: pp. 547554 : ill. includes bibliography 
summary 
The geometric structure inherent in the definition of the shapes of threedimensional objects and environments is used not just to define their relative motion and placement, but also to assist in solving many other problems of systems for producing pictures by computers. By using an extension of traditional structure information, or a geometric hierarchy, five significant improvements to current techniques are possible. First, the range of complexity of an environment is greatly increased while the visible complexity of any given scene is kept within a fixed upper limit. Second, a meaningful way is provided to vary the amount of detail presented in a scene. Third, 'clipping' becomes a very fast logarithmic search for the resolvable parts of the environment within the field of view. Fourth, frame to frame coherence and clipping define a graphical 'working set,' or fraction of the total structure that should be present in primary store for immediate access by the visible surface algorithm. Finally, the geometric structure suggests a recursive descent, visible surface algorithm in which the computation time potentially grows linearly with the visible complexity of the scene 
keywords 
hidden lines, hidden surfaces, data structures, clipping, geometric modeling, algorithms, computer graphics 
series 
CADline 
references 
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last changed 
2003/06/02 11:58 
