Files in this item
Files  Description  Format 

application/pdf 9512544.pdf (4MB)  (no description provided) 
Description
Title:  Topological modeling with simplicial complexes 
Author(s):  Shah, Nimish Rameshbhai 
Doctoral Committee Chair(s):  Edelsbrunner, Herbert 
Department / Program:  Computer Science 
Discipline:  Computer Science 
Degree Granting Institution:  University of Illinois at UrbanaChampaign 
Degree:  Ph.D. 
Genre:  Dissertation 
Subject(s):  Computer Science 
Abstract:  Simplicial complexes are useful for modeling shape of a discrete geometric domain and for discretizing continuous domains. A geometric triangulation of a point set S is a simplicial complex whose vertex set is contained in S and whose underlying space is the convex hull of S. In this thesis we study different approaches for constructing subcomplexes of a geometric triangulation to obtain a good model of a given domain. The work described in this thesis is about regular triangulations, weighted $\alpha$shapes and homeomorphic triangulations. We develop the notion of a regular triangulation of a set on n weighted points in general position in $\IR\sp{d}$. Regular triangulations generalise Delaunay triangulations, and are related to convex hulls in $\IR\sp{d+1}$. We present an efficient randomized incremental algorithm for computing the regular triangulation of a finite weighted point set in $\IR\sp{d}$. The expected running time for the worst set of n points in $\IR\sp{d}$ is O($n\log n$ + $n\sp{\lceil d/2\rceil}$). We also discuss some implementation issues related to degenerate point sets. For $\alpha$ $\in$ $\IR$, a weighted $\alpha$shape of a finite set of weighted points in $\IR\sp{d}$ is obtained from a subcomplex of the regular triangulation of the point set. Weighted $\alpha$shapes are useful for molecular modeling and surface reconstruction. We present a definition for weighted $\alpha$shapes that applies to any input, including degenerate data. We also give a straightforward algorithm to compute them. Finally, we introduce the Delaunay simplicial complex of a point set S restricted by a given topological space, a subset of $\IR\sp{d}$. This concept is useful in discretizing continuous domains, especially when the dimension of the domain and the imbedding dimension are different. The restricted Delaunay simplicial complex is a subcomplex of the Delaunay triangulation of S. We present sufficient conditions for the underlying space of the restricted Delaunay simplicial complex to be homeomorphic to the given topological space. 
Issue Date:  1994 
Type:  Text 
Language:  English 
URI:  http://hdl.handle.net/2142/20105 
Rights Information:  Copyright 1994 Shah, Nimish Rameshbhai 
Date Available in IDEALS:  20110507 
Identifier in Online Catalog:  AAI9512544 
OCLC Identifier:  (UMI)AAI9512544 
This item appears in the following Collection(s)

Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois 
Dissertations and Theses  Computer Science
Dissertations and Theses from the Dept. of Computer Science