Showing papers on "Point (geometry) published in 1998"
TL;DR: By analyzing the scale-space behavior of a model line profile, it is shown how the bias that is induced by asymmetrical lines can be removed and the algorithm not only returns the precise subpixel line position, but also the width of the line for each line point, also with subpixel accuracy.
Abstract: The extraction of curvilinear structures is an important low-level operation in computer vision that has many applications. Most existing operators use a simple model for the line that is to be extracted, i.e., they do not take into account the surroundings of a line. This leads to the undesired consequence that the line will be extracted in the wrong position whenever a line with different lateral contrast is extracted. In contrast, the algorithm proposed in this paper uses an explicit model for lines and their surroundings. By analyzing the scale-space behavior of a model line profile, it is shown how the bias that is induced by asymmetrical lines can be removed. Furthermore, the algorithm not only returns the precise subpixel line position, but also the width of the line for each line point, also with subpixel accuracy.
1,200 citations
Patent•
23 Oct 1998
TL;DR: In this paper, a scanning laser device scans the 3D object and generates a point cloud, where points of the point cloud each indicate a location of a corresponding point on a surface of the object.
Abstract: An integrated system generates a model of a three-dimensional object. A scanning laser device scans the three-dimensional object and generates a point cloud. The points of the point cloud each indicate a location of a corresponding point on a surface of the object. A first model is generated, responsive to the point cloud, that generates a first model representing constituent geometric shapes of the object. A data file is generated, responsive to the first model, that can be inputted to a computer-aided design system.
1,005 citations
01 Jan 1998
TL;DR: The first edition of this book is recognised as one of the definitive sources on the subject of Computational Geometry and the second edition is a welcome addition to my bookshelf.
Abstract: The first edition of this book is recognised as one of the definitive sources on the subject of Computational Geometry. In fact, O'Rourke has a long history in the field, has published many papers on the subject and is responsible for the computer graphics algorithms newsgroup which is where all computer geometers meet to discuss their ideas and problems. Typical problems discussed include how a polygon can be represented, how to calculate its area, how to detect if two polygons intersect and how to calculate the convex hull of a polygon. This leads onto more complex issues such as motion planning and seeing if a robot is able navigate from point x to point y without bumping into objects. The algorithms for these (and other) problems are discussed and many are implemented. In addition, many of the ideas are also discussed from the point of view of three and more dimensions. The only disappointment is that many problems are posed as questions at the end of the chapters and, as far as I could see, you cannot get the answers in the forms of a lecturer's supplement. This is fine in academia but not a lot of use for the commercial world. Due to the range of problems that incorporate computational geometry this book cannot be expected to answer every problem you might have. You will undoubtedly need access to other textbooks but I have been using the first edition of this book for many years and the second edition is a welcome addition to my bookshelf. If I was only allowed one computational geometry book then it would undoubtedly be this one.
823 citations
TL;DR: A microprocessor controlled cathode ray tube display system has a plurality of peripheral devices all connected in common to a system bus that enables the interrupting device to place its address signals on the system bus thereby initiating a firmware routine for making the interrupted device operative with the system.
Abstract: We study all three-point functions of normalized chiral operators in D=4, $\CN=4$, U(N) supersymmetric Yang-Mills theory in the large $N$ limit. We compute them for small 't Hooft coupling $\lambda=g_{YM}^2N >1$ using the $AdS$/CFT correspondence. Surprisingly, we find the same answers in the two limits. We conjecture that at least for large $N$ the exact answers are independent of $\lambda $ .
635 citations
TL;DR: In this article, a nonlinear model in the form of a mapping from one point of observation to the next has been derived, which has a closed form even when the parasitic elements are included.
Abstract: The occurrence of nonlinear phenomena like subharmonics and chaos in power electronic circuits has been reported recently. In this paper, the authors investigate these phenomena in the current-mode-controlled boost power converter. A nonlinear model in the form of a mapping from one point of observation to the next has been derived. The map has a closed form even when the parasitic elements are included. The bifurcation behavior of the boost power converter has been investigated with the help of this discrete model.
197 citations
TL;DR: A new approach to mobile robot position estimation, based on principal component analysis of laser range data, is described, which converts the problem of associating a range profile to possible positions and orientations into a table lookup.
106 citations
02 Jun 1998
TL;DR: An analytic solution for solving the problem of a simultaneous registration of M point sets, M>2, by rigid motions is presented, based on the use of unit quaternions for the representation of the rotations.
Abstract: Registering 3D point sets is a common problem in computer vision. The case of two point sets has been analytically well solved by several authors. In this paper we present an analytic solution for solving the problem of a simultaneous registration of M point sets, M>2, by rigid motions. The solution is based on the use of unit quaternions for the representation of the rotations.
103 citations
Patent•
23 Feb 1998
TL;DR: In this article, a method of path planning, comprising providing a dataset representing a cavity and a boundary, providing a plurality of points in said dataset, including at least a starting point and an ending point, was proposed.
Abstract: A method of path planning, comprising providing a dataset representing a cavity and a boundary; providing a plurality of points in said dataset, including at least a starting point and an ending point; and automatically determining a path between the starting point and the ending point, responsive to a penalty associated with passing through points in the cavity. Preferably, the penalty value associated with a point depends on a distance between the point and the boundary.
91 citations
TL;DR: In this article, the specification dictated by the specification of a granular ensemble is given and it is argued that randomly shaped, incompressible and perfectly rough grains, all suffer four point contacts.
Abstract: The specification dictated by the specification of a granular ensemble is given and it is argued that randomly shaped, incompressible and perfectly rough grains, all suffer four point contacts. A hierarchy of functions which describe the static equilibrium is set up, and equations for these functions are established. Some applications are briefly discussed.
79 citations
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01 Jan 1998
TL;DR: It is shown that small intestinal submucosa seeded with cells from human anulus fibrosus and nucleus pulposus can be cultured for 3 months without significant loss of metabolic activities of the cells.
Abstract: This article is about a pilot study investigating small intestinal submucosa as a potential bioscaffold for intervertebral disc regeneration. Le Visage et al have shown that small intestinal submucosa seeded with cells from human anulus fibrosus and nucleus pulposus can be cultured for 3 months without significant loss of metabolic activities of the cells. The data indicate some loss of cells or apoptosis as the deoxyribonucleic acid content decreased with time, but the metabolic activities as measured by glycosaminoglycan and collagen contents and gene expressions of aggrecan, collagen I, II, and X, and Sox-9 remained throughout the culture period. It was surprising to note that there was no appreciable difference between nucleus pulposus and anulus fibrosus cells, but it might be explained by difficulty distinguishing nucleus pulposus and anulus fibrosus tissues from human samples. The authors have measured the total glycosaminoglycan content but have not measured the synthetic activity of proteoglycans, which might be more important in assessing the metabolic activity of the cells. It would also be helpful to know the biomechanical or handling characteristics of the tissue engineered constructs for potential clinical applicability of intervertebral disc injection. The results of this study should be interpreted with caution in that the microenvironment of the cells in vivo is quite different from the in vitro culture condition, such as nutrition, oxygen tension, pH, etc. The next steps for further research would be to test this construct in an organ culture and in vivo animal models. The reader should understand that other scaffolds or scaffold-free tissue engineering constructs have been investigated, such as collagen gels, alginate, etc. How small intestinal submucosa compares to other constructs would be interesting to study in the future. Finally, the reader should understand the larger context of potential biologic treatments for intervertebral disc degeneration and how tissue engineered constructs such as small intestinal submucosa might be applicable. In early-tointermediate intervertebral disc degeneration, injection of proteins such growth factors, bone morphogenetic proteins, and blockers of pro-inflammatory cytokines alone might be sufficient as long as the resident intervertebral disc cells have sufficient nutrients and an appropriate microenvironment for these proteins to interact with cells and upregulate and maintain matrices. At a later stage of intervertebral disc degeneration in which the cells have become mostly apoptotic, injection of cells with or without scaffold might be considered. Tissue engineered constructs may also be applied for repair of anulus fibrosus tears as well. Further research on these constructs with appropriate animal models will give better insights into the potential applicability to human degenerating intervertebral disc. From the Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. Address correspondence and reprint requests to Howard S. An, MD, Department of Orthopaedic Surgery, Rush University Medical Center, Suite 1063; 1725 W. Harrison Street, Chicago, IL 60612-3824; E-mail: han@ortho4.pro.rpslmc.edu
72 citations
TL;DR: A combinatorial-geometric quantity λ(P, Q) is introduced, which is called the inner product of the distance-multiplicity vectors of P and Q, and it is shown its relevance to the complexity of various algorithms for LCP, and some upper bounds on the quantity are given.
Abstract: This paper considers the following problem, which we call the largest common point set problem (LCP): given two point sets P and Q in the Euclidean plane, find a subset of P with the maximum cardinality that is congruent to some subset of Q . We introduce a combinatorial-geometric quantity λ(P, Q) , which we call the inner product of the distance-multiplicity vectors of P and Q , show its relevance to the complexity of various algorithms for LCP, and give a nontrivial upper bound on λ(P, Q) . We generalize this notion to higher dimensions, give some upper bounds on the quantity, and apply them to algorithms for LCP in higher dimensions. Along the way, we prove a new upper bound on the number of congruent triangles in a point set in four-dimensional space.
01 Jan 1998
TL;DR: In this article, the concept of (t, m, s)-nets and of (m, s)sequences has been shown to be the most powerful basic concept for the construction of low-discrepancy point sets and point sequences.
Abstract: In recent years the concept of (t, m, s)-nets and of (t, s)-sequences has turned out to be the - until now - by far most powerful basic concept for the construction of low-discrepancy point sets and point sequences in an s-dimensional unit cube.
TL;DR: In this article, a mechanistic model is developed to predict the forces for arbitrary drill point geometry, where the cutting lips are divided into elements and the elemental forces are determined from a fundamental oblique cutting model.
Abstract: A mechanistic model is developed to predict the forces for arbitrary drill point geometry. The cutting lips are divided into elements and the elemental forces are determined from a fundamental oblique cutting model. A method is developed to parametrically define the cutting lip in three-dimensional space and to determine the oblique cutting parameters (cutting angles and chip thickness) at each element on the cutting lip. The model does not require calibration experiments for each point geometry. The conical drill is used to determine the model coefficients for a tool and workpiece material combination and these are used for other drill point geometry. Model simulations match experimental data very well for four commercial drill point geometry-the Racon, Helical, Bickford and Double angle drill points.
TL;DR: In this paper, the shape of a heat-generating volume can be optimized to minimize the thermal resistance between the volume and a point heat sink, which is used to solve the kinematics problem of minimizing the time of travel between a volume (or area) and one point.
Abstract: The geometric form of the tree network is deduced from a single mechanism. The discovery that the shape of a heat-generating volume can be optimized to minimize the thermal resistance between the volume and a point heat sink, is used to solve the kinematics problem of minimizing the time of travel between a volume (or area) and one point. The optimal path is constructed by covering the volume with a sequence of volume sizes (building blocks), which starts with the smallest size and continues with stepwise larger sizes (assemblies). Optimized in each building block is the overall shape and the angle between constituents. The speed of travel may vary from one assembly size to the next, however, the lowest speed is used to reach the infinity of points located in the smallest volume elements. The volume-to-point path that results is a tree network. A single design principle – the geometric optimization of volume-to-point access – determines all the features of the tree network.
TL;DR: In this article, an algorithm to construct boundary-conforming, isotropic clouds of points with variable density in space is described, where one point at a time is removed and surrounded by admissible new points.
Abstract: An algorithm to construct boundary-conforming, isotropic clouds of points with variable density in space is described. The input required consists of a specified mean point distance and an initial triangulation of the surface. Borrowing a key concept from advancing front grid generators, one point at a time is removed and, if possible, surrounded by admissible new points. This operation is repeated until no active points are left. Timings show that the scheme is about an order of magnitude faster than volume grid generators based on the advancing front technique, making it possible to generate large (>106) yet optimal clouds of points in a matter of minutes on a workstation. Several examples are included that demonstrate the capabilities of the technique. Copyright © 1998 John Wiley & Sons, Ltd.
01 Jan 1998
TL;DR: This contribution will discuss the main concepts to assess equidistribution and present a new interpretation of the well-known spectral test, which is based on the quasi-Monte Carlo method.
Abstract: The Monte Carlo and the quasi-Monte Carlo method are two of the most important techniques to solve multidimensional problems. In both cases, we employ deterministic algorithms to generate finite point sets in high dimensions. The quality of the equidistribution of these point sets may have a decisive influence on our numerical results. In this contribution, we will discuss the main concepts to assess equidistribution. In particular, we will present a new interpretation of the well-known spectral test.
TL;DR: In this paper, the authors present a framework for the design, manufacture, and evaluation of planar micro-drills with curved helical point and flute geometry. But they focus on the flute and not on the flank.
01 Apr 1998
TL;DR: This work believes that theirs is the first global solution to the moving-obstacle path-planning problem which uses vector fields, and constructs a vector field whose flow is in fact one such deformation.
Abstract: Inspired by an idea of Rimon and Koditschek (1992), we develop a motion planning algorithm for a point robot traveling among moving obstacles in an N-dimensional space. The navigating point must meet a goal point at a fixed time T, while avoiding several translating, nonrotating, nonintersecting obstacles on its way. All obstacles, the goal point, and the navigating point are confined to the interior of a star-shaped set in R/sup N/ over the time interval [0, T]. Full a priori knowledge of the goal's location and of the obstacle's trajectories is assumed. We observe that the topology of the obstacle-free space is invariant in the time interval [0, T] as long as the obstacles are nonintersecting and as long as they do not cover the goal point at any time during [0, T]. Using this fact we reduce the problem, for any fixed time t/sub 0//spl isin/[0, T], to a stationary-obstacle problem, which is then solved using the method of Rimon and Koditschek. The fact that the obstacle-free space is topologically invariant allows a solution to the moving-obstacle problem over [0, T] through a continuous deformation of the stationary-obstacle solution obtained at time t/sub 0/. We construct a vector field whose flow is in fact one such deformation. We believe that ours is the first global solution to the moving-obstacle path-planning problem which uses vector fields.
TL;DR: A general framework for non-commutative geometry is developed from the point of view of supersymmetry and illustrated in terms of examples in this paper, where the noncommutativity torus and the non commutative 3-sphere are studied in some detail.
Abstract: Classical differential geometry can be encoded in spectral data, such as Connes' spectral triples, involving supersymmetry algebras. In this paper, we formulate non-commutative geometry in terms of supersymmetric spectral data. This leads to generalizations of Connes' non-commutative spin geometry encompassing non-commutative Riemannian, symplectic, complex-Hermitian and (Hyper-)Kaehler geometry. A general framework for non-commutative geometry is developed from the point of view of supersymmetry and illustrated in terms of examples. In particular, the non-commutative torus and the non-commutative 3-sphere are studied in some detail.
Patent•
30 Jun 1998TL;DR: In this article, a plurality of images (22, 23) are captured of the object and a first point in a marker from one of the images and a line equation corresponding to the first point is determined.
Abstract: A method and apparatus (20) for extracting three-dimensional (3D) data from a target object using a plurality of markers formed on the object. A plurality of images (22, 23) are captured of the object. A first point is designated from a marker from one of the images and a line equation corresponding to the first point is determined. A second point in a marker in another image corresponding to the first point is determined and a second line equation corresponding to the second point is determined. The intersection of the two line equations is then determined using a computing device (19).
TL;DR: In this paper, the geometrical structure of the set M of configurations of a mechanism is analyzed using Lie groups language and without any hypothesis of regularity, one can attach to this set a structure of an analytic variety.
Abstract: In this article, we analyse the geometrical structure of the set M of configurations of a mechanism. Using Lie groups language and without any hypothesis of regularity, one can attach to this set a structure of an analytic variety. We shall then compute the tangent cone at cach point of this set without introducing any coordinates and we shall deduce the structure of M whatever the singularity may be. Finally, some examples are studied.
TL;DR: In this article, a boundary-element method was proposed to identify the strength of line heat sources when their position is known, and a regularization procedure over some future time steps was used to solve the ill-posed problem correctly.
Abstract: This article deals with an inverse problem relative to point heat source identification in homogeneous solids. Using the boundary-element method, it is proposed to identify the strength of line heat sources when their position is known. To solve the inverse problem, some internal temperatures at prescribed locations are given. A regularization procedure over some future time steps is used to solve the ill-posed problem correctly. To test the method, some disrupt data provided by numerical simulation are used. Different solicitations are shown, and an example involving two line sources is presented.
Patent•
04 May 1998
TL;DR: In this paper, an improved method and apparatus for the production of superior quality 3D images utilizing a multi-lens camera and a multilens enlarger configured according to a standard of arrangements is presented.
Abstract: An improved method and apparatus for the production of superior quality three dimensional images utilizing a multi-lens camera and a multi-lens enlarger configured according to a standard of arrangements. The number of lenses used in the camera and the enlarger is selected to he greater than the resolution capabilities of the human eye and the lenticular print system. The width of a zone of the lineiform image is determined by the distance between two adjacent images on the focal plane of the lenticular screen of a point projected from a distance at or beyond the distance limit through adjacent projecting apertures of the enlarger. The projecting apertures of the enlarger are linearly arrayed and equally spaced within the accepting angle corresponding to the distance limit to construct a lineiform image without gaps between zones and without gaps between lines. Accordingly, a three dimensional image having orthoscopic effect, without stroboscopic effect, is produced in a one-step imaging and one-step composing process.
09 Nov 1998
TL;DR: The approach to initial mesh creation is based on extraction of points from the cloud based on geometric relationships with nearby points, which are linked to construct a polygonal mesh that is then triangulated.
Abstract: Surface reconstruction from point clouds is an important element of reverse engineering as used to create solid models of existing objects. The research presented in this paper assumes no knowledge of relationships among the elements of the point cloud. The approach to initial mesh creation is based on extraction of points, called “feature points”, from the cloud based on geometric relationships with nearby points. A neighborhood is established for each data point, the points in the neighborhood are ordered, and feature points are identified based on relationships among the neighbors. Feature points within a neighborhood are linked to construct a polygonal mesh that is then triangulated.
TL;DR: It is experimentally demonstrated that the proposed control laws realize higher acceleration and lower reaction force than other force display systems.
Abstract: In this paper, we develop a force display system using parallel wire mechanism for virtual sports training with high speed motion. We firstly point out a control issue of the force display system driven by parallel wire mechanism. Based on the analysis, control laws are proposed to improve performance of the force display system. It is experimentally demonstrated that the proposed control laws realize higher acceleration and lower reaction force than other force display systems. Using the experimental result, the performance of the system is evaluated quantitatively.
TL;DR: In this paper, the authors consider the point-line geometries that arise as a shadow space in a spherical building with a diagram of type An, Bn, Cn, Dn or En, and determine in which cases the geometry is spanned by the set of points on an apartment.
Abstract: We consider the point-line geometries that arise as a shadow space in a spherical building with a diagram of type An, Bn, Cn, Dn or En, and determine in which cases the geometry is spanned by the set of points on an apartment. It turns out that this happens precisely in the cases corresponding to a minimal weight.
Patent•
IBM1
TL;DR: In this article, a method for deriving a single dimensional representation for a set of points e.g., minutiae, in image of a two dimensional pattern of lines, e. g. a fingerprint, by creating a one dimensional representation of one or more points and the respective attributes of each point therein is presented.
Abstract: The invention is a system and method for deriving a single dimensional representation for a set of points e.g.,minutiae, in image of a two dimensional pattern of lines, e.g. a fingerprint, by creating a one dimensional (string) representation of one or more points (e.g., minutiae) and the respective attributes of each point therein. A landmark point is selected from the two dimensional image, preferably from the set of the points to be represented in single dimension. The relationships of each of the points with reference to the landmark determines a linear order for the points and the attributes associated with each point.
Patent•
04 Mar 1998
TL;DR: In this article, a method of determining collision occurring in a virtual space generated by a system using a computer includes the steps of preparing, for drawing data approximating a virtual object in the virtual space by a plurality of rectangular parallelepipeds, machine readable first shape data for collision determination approximating the virtual object by a smaller in number than rectangular paralleler.
Abstract: A method of determining collision occurring in a virtual space generated by a system using a computer includes the steps of preparing, for drawing data approximating a virtual object in the virtual space by a plurality of rectangular parallelepipeds, machine readable first shape data for collision determination approximating the virtual object by a plurality of rectangular parallelepipeds smaller in number than rectangular parallelepipeds of the drawing data, and determining, as a prescribed point moving in the virtual space moves, whether the prescribed point and the virtual object satisfy a predetermined collision condition or not, based on a coordinate of the prescribed point in the virtual space and the first shape data, by computer calculation. An apparatus for implementing this method is also disclosed.