Topology evolutions of silhouettes  

作　　者：DAI Jun-fei KIM Junho ZENG Hua-yi GU Xian-feng YAU Shing-tung 

机构地区：[1]Center of Mathematical Sciences, Zhejiang University, Hangzhou 310027, China [2]Visualization Laboratory, State University of New York, Stony Brook, NY 11794, USA [3]Department of Mathematics, Harvard University, Boston MA02138, USA

出　　处：《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》2007年第10期1671-1680,共10页浙江大学学报（英文版）A辑（应用物理与工程）

基　　金：Project supported by the NSF CAREER Award (Nos. CCF-0448339 and DMS-0528363) of the USA;the National Natural Science Foundation of China (No. 60503067)

摘　　要：We give the topology changing of the silhouette in 3D space while others study the projections in an image. Silhou- ettes play a crucial role in visualization, graphics and vision. This work focuses on the global behaviors of silhouettes, especially their topological evolutions, such as splitting, merging, appearing and disappearing. The dynamics of silhouettes are governed by the topology, the curvature of the surface, and the view point. In this paper, we work on a more theoretical level to give enu- merative properties of the silhouette including: the integration of signed geodesic curvature along a silhouette is equal to the view cone angle; in elliptic regions, no silhouette can be contained in another one; in hyperbolic regions, if a silhouette is homotopic to a point, then it has at least 4 cusps; finally, critical events can only happen when the view point is on the aspect surfaces (ruled surface of the asymptotic lines of parabolic points with surface itself). We also introduce a method to visualize the evolution of silhouettes, especially all the critical events where the topologies of the silhouettes change. The results have broad applications in computer vision for recognition, graphics for rendering and visualization.We give the topology changing of the silhouette in 3D space while others study the projections in an image. Silhouettes play a crucial role in visualization, graphics and vision. This work focuses on the global behaviors of silhouettes, especially their topological evolutions, such as splitting, merging, appearing and disappearing. The dynamics of silhouettes are governed by the topology, the curvature of the surface, and the view point. In this paper, we work on a more theoretical level to give enumerative properties of the silhouette including： the integration of signed geodesic curvature along a silhouette is equal to the view cone angle; in elliptic regions, no silhouette can be contained in another one; in hyperbolic regions, if a silhouette is homotopic to a point, then it has at least 4 cusps; finally, critical events can only happen when the view point is on the aspect surfaces （ruled surface of the asymptotic lines of parabolic points with surface itself）. We also introduce a method to visualize the evolution of silhouettes, especially all the critical events where the topologies of the silhouettes change. The results have broad applications in computer vision for recognition, graphics for rendering and visualization.

关 键 词：Topological change SILHOUETTE Geodesic curvature CUSP 

分 类 号：O29[理学—应用数学] TP391[理学—数学]