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International Conference on computer Vision (ICCV)

作者： L. Zelnik-Manor M. Irani Department of Computer Science and Applied Math Weizmann Institute of Science Rehovot Israel

The motion of a planar surface between two camera views induces a homography. The homography depends on the camera intrinsic and extrinsic parameters, as well as on the 3D plane parameters. While camera parameters vary across different views, the plane geometry remains the same. Based on this fact, the paper derives linear subspace constraints on the relative motion of multiple (/spl ges/2) planes across multiple views. The paper has three main contributions. It shows that the collection of all relative homographies of a pair of planes (homologies) across multiple views, spans a 4-dimensional linear subspace. It shows how this constraint can be extended to the case of multiple planes across multiple views. It suggests two potential application areas which can benefit from these constraints: the accuracy of homography estimation can be improved by enforcing the multi-view subspace constraints; and violations of these multi-view constraints can be used as a cue for moving object detection. All the results derived in this paper are true for uncalibrated cameras.

关键词： Subspace constraints Cameras Layout Geometry Object detection Transmission line matrix methods computer science Calibration Algorithm design and analysis

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Multi-frame alignment of planes

Multi-frame alignment of planes

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Conference on computer Vision and Pattern Recognition (CVPR)

作者： L. Zelnik-Manor M. Irani Department of Computer Science and Applied Math Weizmann Institute of Science Rehovot Israel

Traditional plane alignment techniques are typically performed between pairs of frames. In this paper we present a method for extending existing two-frame planar-motion estimation techniques into a simultaneous multi-frame estimation, by exploiting multi-frame geometric constraints of planar surfaces. The paper has three main contributions: (i) we show that when the camera calibration does not change, the collection of all parametric image motions of a planar surface in the scene across multiple frames is embedded in a low dimensional linear subspace; (ii) we show that the relative image motion of multiple planar surfaces across multiple frames is embedded in a yet lower dimensional linear subspace, even with varying camera calibration; and (iii) we show how these multi-frame constraints can be incorporated into simultaneous multi-frame estimation of planar motion, without explicitly recovering any 3D information, or camera calibration. The resulting multi-frame estimation process is more constrained than the individual two-frame estimations, leading to more accurate alignment, even when applied to small image regions.

关键词： Motion estimation Subspace constraints Cameras Calibration Layout computer science Visualization Object detection Robustness Geometry

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Green's function contact maps for accurate real time collisions

Green's function contact maps for accurate real time collisi...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： C. Ullrich D.K. Pai Institute of Applied Math University of British Columbia Vancouver BC Canada Department of Computer Science University of British Columbia Vancouver BC Canada

In this article, we discuss the application, of a Green's function approach to contact maps. We apply the contact map algorithm to the case of an elastic bar impacting on a massive foundation. It is demonstrated t... 详细信息

关键词： Green's function methods Solid modeling Computational modeling Energy loss Boundary element methods Telerobotics Virtual environment Partial differential equations Iris computer science

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Shape reconstruction of 3D bilaterally symmetric surfaces

Shape reconstruction of 3D bilaterally symmetric surfaces

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International Conference on Image Analysis and Processing

作者： I. Shimshoni Y. Moses M. Lindenbaumlpr Department of Industrial Engineering & Management Technion-Israel Institute of Technology Haifa Israel Department of Applied Math Weizmann Institute of Science Rehovot Israel Department of Computer Science Technion-Israel Institute of Technology Haifa Israel

The paper presents a new approach for shape recovery based on integrating geometric and photometric information. We consider 3D objects which are symmetric with respect to a plane (e.g., faces) and their reconstruction from a single image. Both the viewpoint and the illumination are not necessarily frontal. In principle, no correspondence between symmetric points is required, but knowledge about a few corresponding pairs accelerates the process. The basic idea is that an image taken from a general, non-frontal viewpoint, under non-frontal illumination can be regarded as a pair of images of half of the object, taken from two different viewing positions and two different lighting directions. We show that integrating the photometric and geometric information yields the unknown lighting and viewing parameters, as well as dense correspondence between pairs of symmetric points. As a result, a dense shape recovery of the object is computed. The method has been implemented and tested experimentally on simulated and real data.

关键词： Shape Surface reconstruction Electrical capacitance tomography Image reconstruction Photometry Lighting computer science Programmable logic arrays Read only memory Neutron spin echo

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Image-based robot navigation under the perspective model

Image-based robot navigation under the perspective model

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IEEE International Conference on Robotics and Automation (ICRA)

作者： R. Basri E. Rivlin I. Shimshoni Department of Applied Math Weizmann Institute of Science Rehovot Israel Department of Computer Science Technion-Israel Institute of Technology Haifa Israel Department of Ind. Engineering and Mgmt. Technion-Israel Institute of Technology Haifa Israel

In a previous paper (1998) we presented a method for image-based navigation by which a robot can navigate to desired positions and orientations in 3D space specified by single images taken from these positions. In this paper we further investigate the method and develop robust algorithms for navigation assuming the perspective projection model. In particular, we develop a tracking algorithm that exploits our knowledge of the motion performed by the robot at every step. This algorithm allows us to maintain correspondences between frames and eliminate false correspondences. We combine this tracking algorithm with an iterative optimization procedure to accurately recover the displacement of the robot from the target. Our method for navigation is attractive since it does not require a 3D model of the environment. We demonstrate the robustness of our method by applying it to a six degree of freedom robot arm.

关键词： Navigation Orbital robotics Robustness Iterative algorithms Target tracking computer science Robot vision systems Cameras Career development Visual servoing

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A framework for scheduler synthesis

A framework for scheduler synthesis

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Real-Time Systems Symposium (RTSS)

作者： K. Altisen G. Gossler A. Pnueli J. Sifakis S. Tripakis S. Yovine Verimag Centre Equation Gieres France VERIMAG Saint-Martin-d'Heres Auvergne-RhÃ´ne-Alpes FR Department Computer Science and Applied Math Weizmann Institute of Science Rehovot Israel

We present a framework integrating specification and scheduler generation for real time systems. In a first step, the system, which can include arbitrarily designed tasks (cyclic or sporadic, with or without precedence constraints, any number of resources and CPUs) is specified as a timed Petri net. In a second step, our tool generates the most general non preemptive online scheduler for the specification, using a controller synthesis technique.

关键词： Real time systems Processor scheduling Automata Delay Synchronization Resource management Equations computer science Buildings Application software

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Information retrieval from annotated texts

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Journal of the Association for Information science and Technology 1999年第10期50卷

作者： Aviezri S. Fraenkel Shmuel T. Klein Department of Applied Math & Computer Science The Weizmann Institute of Science Rehovot 76100 Israel Department of Math & Computer Science Bar-Ilan University Ramat-Gan 52900 Israel

Methods for the correct and efficient handling of annotations in a full-text retrieval system were investigated. The problem with annotations is that they cannot be treated as regular text, since this would disrupt proximity searches, but on the other hand, they cannot be ignored, as they may carry important information. Moreover, in some cases, a user may wish to restrict a search to prespecified subsets of annotations. We suggest a new way of processing the database to overcome the above dilemma.

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Approximating the bandwidth via volume respecting embeddings (extended abstract) 98

Approximating the bandwidth via volume respecting embeddings...

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Proceedings of the thirtieth annual ACM symposium on Theory of computing

作者： Uriel Feige Department of Applied Math and Computer Science The Weizmann Institute Rehovot 76100 Israel

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Heuristics for finding large independent sets, with applications to coloring semi-random graphs

Heuristics for finding large independent sets, with applicat...

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Annual IEEE Symposium on Foundations of computer science

作者： U. Feige J. Kilian Department of Applied Math and Computer Science Weizmann Institute of Science Rehovot Israel NEC Research Institute Inc. Princeton NJ USA

We study a semi-random graph model for finding independent sets. For /spl alpha/>0, an n-vertex graph with an independent set S of site /spl alpha/n is constructed by blending random and adversarial decisions. Randomly and independently with probability p, each pair of vertices, such that one is in S and the other is not, is connected by an edge. An adversary can then add edges arbitrarily (provided that S remains an independent set). The smaller p is, the larger the control the adversary has over the semi-random graph. We design heuristics that with high probability recover S when p>(1+/spl epsiv/)ln n/|S|, for any constant /spl epsiv/>0. We show that when p

关键词： Electronic switching systems National electric code computer science Career development Polynomials Performance evaluation

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Clustering appearances of 3D objects

Clustering appearances of 3D objects

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Conference on computer Vision and Pattern Recognition (CVPR)

作者： R. Basri D. Roth D. Jacobs Department of Applied Math Weizmann Institute of Science Rehovoth Israel Department of Computer Science University of Illinois Urbana IL USA NEC Research Institute Inc. Princeton NJ USA

We introduce a method for unsupervised clustering of images of 3D objects. Our method examines the space of all images and partitions the images into sets that form smooth and parallel surfaces in this space. It further uses sequences of images to obtain more reliable clustering. Finally, since our method relies on a non-Euclidean similarity measure we introduce algebraic techniques for estimating local properties of these surfaces without first embedding the images in a Euclidean space. We demonstrate our method by applying it to a large database of images.

关键词： Distortion measurement Image databases Shape Jacobian matrices computer science National electric code Extraterrestrial measurements computer vision Humans Visual system

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