Results 1  10
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50
Robot Pose Estimation in Unknown Environments by Matching 2D Range Scans
, 1994
"... A mobile robot exploring an unknown environment has no absolute frame of reference for its position, other than features it detects through its sensors. Using distinguishable landmarks is one possible approach, but it requires solving the object recognition problem. In particular, when the robot use ..."
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Cited by 274 (9 self)
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A mobile robot exploring an unknown environment has no absolute frame of reference for its position, other than features it detects through its sensors. Using distinguishable landmarks is one possible approach, but it requires solving the object recognition problem. In particular, when the robot uses twodimensional laser range scans for localization, it is difficult to accurately detect and localize landmarks in the environment (such as corners and occlusions) from the range scans. In this paper, we develop two new iterative algorithms to register a range scan to a previous scan so as to compute relative robot positions in an unknown environment, that avoid the above problems. The first algorithm is based on matching data points with tangent directions in two scans and minimizing a distance function in order to solve the displacementbetween the scans. The second algorithm establishes correspondences between points in the two scans and then solves the pointtopoint leastsquares probl...
PiecewiseLinear Interpolation between Polygonal Slices
 Computer Vision and Image Understanding
, 1994
"... In this paper we present a new technique for piecewiselinear surface reconstruction from a series of parallel polygonal crosssections. This is an important problem in medical imaging, surface reconstruction from topographic data, and other applications. We reduce the problem, as in most previous wo ..."
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Cited by 75 (12 self)
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In this paper we present a new technique for piecewiselinear surface reconstruction from a series of parallel polygonal crosssections. This is an important problem in medical imaging, surface reconstruction from topographic data, and other applications. We reduce the problem, as in most previous works, to a series of problems of piecewiselinear interpolation between each pair of successive slices. Our algorithm uses a partial curve matching technique for matching parts of the contours, an optimal triangulation of 3D polygons for resolving the unmatched parts, and a minimum spanning tree heuristic for interpolating between non simply connected regions. Unlike previous attempts at solving this problem, our algorithm seems to handle successfully any kind of data. It allows multiple contours in each slice, with any hierarchy of contour nesting, and avoids the introduction of counterintuitive bridges between contours, proposed in some earlier papers to handle interpolation between multi...
Planar Object Recognition using Projective Shape Representation
 International Journal of Computer Vision
, 1995
"... We describe a model based recognition system, called LEWIS, for the identification of planar objects based on a projectively invariant representation of shape. The advantages of this shape description include simple model acquisition (direct from images), no need for camera calibration or object pos ..."
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Cited by 62 (9 self)
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We describe a model based recognition system, called LEWIS, for the identification of planar objects based on a projectively invariant representation of shape. The advantages of this shape description include simple model acquisition (direct from images), no need for camera calibration or object pose computation, and the use of index functions. We describe the feature construction and recognition algorithms in detail and provide an analysis of the combinatorial advantages of using index functions. Index functions are used to select models from a model base and are constructed from projective invariants based on algebraic curves and a canonical projective coordinate frame. Examples are given of object recognition from images of real scenes, with extensive object libraries. Successful recognition is demonstrated despite partial occlusion by unmodelled objects, and realistic lighting conditions. 1 Introduction 1.1 Overview In the context of this paper, recognition is defined as the prob...
Filling Gaps in the Boundary of a Polyhedron
 Computer Aided Geometric Design
, 1993
"... In this paper we present an algorithm for detecting and repairing defects in the boundary of a polyhedron. These defects, usually caused by problems in CAD software, consist of small gaps bounded by edges that are incident to only one polyhedron face. The algorithm uses a partial curve matching t ..."
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Cited by 40 (4 self)
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In this paper we present an algorithm for detecting and repairing defects in the boundary of a polyhedron. These defects, usually caused by problems in CAD software, consist of small gaps bounded by edges that are incident to only one polyhedron face. The algorithm uses a partial curve matching technique for matching parts of the defects, and an optimal triangulation of 3D polygons for resolving the unmatched parts. It is also shown that finding a consistent set of partial curve matches with maximum score, a subproblem which is related to our repairing process, is NPHard. Experimental results on several polyhedra are presented. Keywords: CAD, polyhedra, gap filling, curve matching, geometric hashing, triangulation. 1 Introduction The problem studied in this paper is the detection and repair of "gaps" in the boundary of a polyhedron. This problem usually appears in polyhedral approximations of CAD objects, whose boundaries are described using curved entities of higher leve...
Optimal Geometric Model Matching Under Full 3D Perspective
, 1994
"... Modelbased object recognition systems have rarely dealt directly with 3D perspective while matching models to images. The algorithms presented here use 3D pose recovery during matching to explicitly and quantitatively account for changes in model appearance associated with 3D perspective. These alg ..."
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Cited by 36 (15 self)
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Modelbased object recognition systems have rarely dealt directly with 3D perspective while matching models to images. The algorithms presented here use 3D pose recovery during matching to explicitly and quantitatively account for changes in model appearance associated with 3D perspective. These algorithms use randomstart local search to find, with high probability, the globally optimal correspondence between model and image features in spaces containing over 2 100 possible matches. Three specific algorithms are compared on robot landmark recognition problems. A fullperspective algorithm uses the 3D pose algorithm in all stages of search while two hybrid algorithms use a computationally less demanding weakperspective procedure to rank alternative matches and updates 3D pose only when moving to a new match. These hybrids successfully solve problems involving perspective, and in less time than required by the fullperspective algorithm.
Partial Surface and Volume Matching in Three Dimensions
 IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE
, 1997
"... In this paper we present a new technique for partial surface and volume matching of images in three dimensions. In this ..."
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Cited by 34 (1 self)
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In this paper we present a new technique for partial surface and volume matching of images in three dimensions. In this
On Parallel Hashing and Integer Sorting
, 1991
"... The problem of sorting n integers from a restricted range [1::m], where m is superpolynomial in n, is considered. An o(n log n) randomized algorithm is given. Our algorithm takes O(n log log m) expected time and O(n) space. (Thus, for m = n polylog(n) we have an O(n log log n) algorithm.) The al ..."
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Cited by 30 (8 self)
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The problem of sorting n integers from a restricted range [1::m], where m is superpolynomial in n, is considered. An o(n log n) randomized algorithm is given. Our algorithm takes O(n log log m) expected time and O(n) space. (Thus, for m = n polylog(n) we have an O(n log log n) algorithm.) The algorithm is parallelizable. The resulting parallel algorithm achieves optimal speed up. Some features of the algorithm make us believe that it is relevant for practical applications. A result of independent interest is a parallel hashing technique. The expected construction time is logarithmic using an optimal number of processors, and searching for a value takes O(1) time in the worst case. This technique enables drastic reduction of space requirements for the price of using randomness. Applicability of the technique is demonstrated for the parallel sorting algorithm, and for some parallel string matching algorithms. The parallel sorting algorithm is designed for a strong and non standard mo...
Partial Matching of Planar Polylines Under Similarity Transformations
 In Proceedings of the 8th Annual Symposium on Discrete Algorithms
, 1997
"... Given two planar polylines T and P with n and m edges, respectively, we present an O(m 2 n 2 ) time, O(mn) space algorithm to find portions of the "text" T which are similar in shape to the "pattern" P . In the common case of a simple pattern, such as a line segment or corner ..."
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Cited by 29 (2 self)
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Given two planar polylines T and P with n and m edges, respectively, we present an O(m 2 n 2 ) time, O(mn) space algorithm to find portions of the "text" T which are similar in shape to the "pattern" P . In the common case of a simple pattern, such as a line segment or corner, m = O(1) and our algorithm requires O(n 2 ) time and O(n) space. We use the wellknown arclength versus cumulative turning angle graph to judge how well a scaled, rotated, and translated version of the pattern matches a piece of the text. Our match scoring function balances the length of a match against the mean squared error in the match; given two matches with the same mean squared error (length), the longer (lower mean squared error) match will have a higher score. The match score is a function of the pattern scale, orientation, and position within the text, and our algorithm seeks to find local maxima of the scoring function. An analytic formula for the highest scoring pattern orientation in terms of sc...
Space Efficient 3D Model Indexing
 In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition
, 1992
"... We show that the set of 2D images produced by the point features of a rigid 3D model can be represented with two lines in two highdimensional spaces. These lines are the lowestdimensional representation possible. We use this result to build a system for representing in a hash table at compile time ..."
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Cited by 29 (4 self)
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We show that the set of 2D images produced by the point features of a rigid 3D model can be represented with two lines in two highdimensional spaces. These lines are the lowestdimensional representation possible. We use this result to build a system for representing in a hash table at compile time, all the images that groups of model features can produce. Then at run time a group of image features can access the table and find all model groups that could match it. This table is efficient in terms of space, and is built and accessed through analytic methods that account for the effect of sensing error. In real images, it reduces the set of potential matches by a factor of several thousand. We also use this representation of a model's images to analyze two other approaches to recognition: invariants, and nonaccidental properties. These are properties of images that some models always produce, and all other models either never produce (invariants) or almost never produce (nonaccidental properties). In several domains we determine when invariants exist. In general we show that there are an infinite set of nonaccidenta properties that are qualitatively similar.
A Methodology for the Representation, Indexing, and Retrieval of Images by Content
 Image and Vision Computing
, 1993
"... This paper considers the requirements for the design and implementation of an image database system which supports the storage and retrieval of images by content. Attention is focused on a specific methodology for the efficient representation,indexing, and retrieval of images based on spatial rel ..."
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Cited by 28 (13 self)
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This paper considers the requirements for the design and implementation of an image database system which supports the storage and retrieval of images by content. Attention is focused on a specific methodology for the efficient representation,indexing, and retrieval of images based on spatial relationships and properties of objects. Images are first decomposed into groups of objects and are indexed by computing addresses to all such groups. This methodology supports the efficient processing of queries by image example and avoids exhaustive searching through the entire image database. The performance of an image database system using the above methodology has been evaluated based on simulated images, as well as images obtained with computed tomography and magnetic resonance imaging. The results of this evaluation are presented and discussed.