Hierarchical Geometric Models for Visible Surface Algorithms The geometric structure inherent in the definition of the shapes of three-dimensional 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 computer. 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. CACM October, 1976 Clark, J. H. visible surface algorithms, hidden surface algorithms, hierarchical data structures, geometric models 5.31 8.2 CA761003 JB January 3, 1978 4:42 PM 1892 4 2828 1901 4 2828 2085 4 2828 2095 4 2828 2218 4 2828 2277 4 2828 2319 4 2828 2329 4 2828 2358 4 2828 2373 4 2828 2380 4 2828 2434 4 2828 2499 4 2828 2501 4 2828 2582 4 2828 2669 4 2828 2674 4 2828 2687 4 2828 2816 4 2828 2828 4 2828 2828 4 2828 2828 4 2828 2828 4 2828 2827 4 2828 2863 4 2828 2881 4 2828 2913 4 2828 2928 4 2828 2996 4 2828 3006 4 2828 3047 4 2828 3067 4 2828 1751 5 2828 2004 5 2828 2751 5 2828 2828 5 2828 2828 5 2828 2828 5 2828 2841 5 2828