This Article 
   
 Share 
   
 Bibliographic References 
   
 Add to: 
 
Digg
Furl
Spurl
Blink
Simpy
Google
Del.icio.us
Y!MyWeb
 
 Search 
   
On Compatible Star Decompositions of Simple Polygons
January-March 1997 (vol. 3 no. 1)
pp. 87-95

Abstract—We introduce the notion of compatible star decompositions of simple polygons. In general, given two polygons with a correspondence between their vertices, two polygonal decompositions of the two polygons are said to be compatible if there exists a one-to-one mapping between them such that the corresponding pieces are defined by corresponding vertices. For compatible star decompositions, we also require correspondence between star points of the star pieces. Compatible star decompositions have applications in computer animation and shape representation and analysis.

We present two algorithms for constructing compatible star decompositions of two simple polygons. The first algorithm is optimal in the number of pieces in the decomposition, providing that such a decomposition exists without adding Steiner vertices. The second algorithm constructs compatible star decompositions with Steiner vertices, which are not minimal in the number of pieces but are asymptotically worst case optimal in this number and in the number of added Steiner vertices. We prove that some pairs of polygons require Ω(n2) pieces, and that the decompositions computed by the second algorithm possess no more than O(n2) pieces.

In addition to the contributions regarding compatible star decompositions, the paper also corrects an error in the only previously published polynomial algorithm for constructing a minimal star decomposition of a simple polygon, an error which might lead to a nonminimal decomposition.

[1] B. Aronov, R. Seidel, and D. Souvaine, "On Compatible Triangulations of Simple Polygons," Computational Geometry: Theory and Applications, vol. 3, no. 1, pp. 27-36, 1993.
[2] E.W. Bethel and S.P. Uselton, "Shape Distortion in Computer-Assisted Keyframe Animation," Computer Animation '89, Magnenat-Thalmann and Thalmann, eds., pp. 215-224.Tokyo: Springer, 1989.
[3] B. Joe and R.B. Simpson, "Visibility of a Simple Polygon from a Point," technical report, Univ. of Waterloo, 1985.
[4] B. Joe and R.B. Simpson,“Corrections to Lee’s visibility polygon algorithm,” BIT, vol. 27, pp. 458-473, 1987.
[5] M. Keil, "Decomposing Polygons into Simpler Components," Technical Report #163/83, Dept. of Computer Science, Univ. of Toronto, 1983.
[6] M. Keil, "Decomposing a Polygon into Simple Components," SIAM J. Computing, vol. 14, pp. 799-817, 1985.
[7] M. Keil Personal communication, 1993.
[8] J.R. Kent, W.E. Carlson, and R.E. Parent, “Shape Transformation for Polyhedral Objects,” Computer Graphics (Proc. SIGGRAPH 92), vol. 26, no. 2, pp. 47-54, July 1992.
[9] J. O'Rourke, Art Gallery Theorems and Algorithms. New York: Oxford Univ. Press, 1987.
[10] A. Saalfeld, "Joint Triangulations and Triangulation Maps," Proc. Third ACM Symp. Computational Geometry, pp. 195-204,Waterloo, Canada, June 1987.
[11] T.W. Sederberg and E. Greenwood, A Physically Based Approach to 2D Shape Blending Proc. SIGGRAPH '92, pp. 25-34, July 1992.
[12] T.W. Sederberg et al., "2D Shape Blending: An Intrinsic Solution to the Vertex Path Problem," Computer Graphics Proc. (Siggraph 93), 1993, ACM, New York, 1993, pp. 15-18.
[13] M. Shapira Etzion and A. Rappoport, "Shape Blending Using the Star-Skeleton Representation," IEEE Computer Graphics and Applications, vol. 15, no. 2, pp. 44-50, Mar. 1995.
[14] M. Shapira Etzion and A. Rappoport, "On Compatible Star Decompositions," technical report, Inst. of Computer Science, The Hebrew Univ. of Jerusalem, 1994.
[15] D. Souvaine and R. Wenger, "Constructing Piecewise Linear Homeomorphisms," manuscript, 1994.

Index Terms:
Star decomposition, minimal star decomposition, compatible decompositions, compatible star decompositions.
Citation:
Michal Etzion, Ari Rappoport, "On Compatible Star Decompositions of Simple Polygons," IEEE Transactions on Visualization and Computer Graphics, vol. 3, no. 1, pp. 87-95, Jan.-March 1997, doi:10.1109/2945.582388
Usage of this product signifies your acceptance of the Terms of Use.