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Geometric spanner is a fundamental structure in computational geometry and plays an important role in many geometric networks design applications. In this paper, we consider a generalization of the classical geometric spanner problem (called segment spanner): Given a set S of n disjoint 2-D segments, find a spanning network GS with minimum size so that for any pair of points in S, there exists a path in GS with length no more than t times their Euclidean distance. Based on a number of interesting techniques (such as weakly dominating set, strongly dominating set, interval cover, and imaginary Steiner points), we present an efficient algorithm to construct the segment spanner. Our approach first identifies a set Q of Steiner points in S and then constructs a point spanner for the set of Steiner points. Our algorithm runs in O(|Q| + n2log n) time and Q is a constant approximation (in terms of its size) of the optimal solution when S has a constant relative separation ratio. The approximation ratio depends on the stretch factor t and the relative separation ratio of S. [ABSTRACT FROM AUTHOR]

In Part I, we described an efficient and robust algorithm for computing a common refinement of two surface meshes. In this paper, we present a theoretical verification of the robustness of our algorithm by showing the topological preservation of the intersection principle, which we used to resolve topological inconsistencies caused by numerical errors. To enhance robustness in practice for complex geometries, we further propose techniques to detect and match geometric features, such as ridges, corners, and nonmatching boundaries. We report experimental results using our enhanced overlay algorithm with feature matching for complex geometries from real-world applications. [ABSTRACT FROM AUTHOR]