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 reconstructio...
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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.
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 thi...
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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.
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 precedenc...
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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.
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 pr...
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.
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. Rand...
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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
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 furth...
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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.
For a graph G, let alpha(G) denote the size of the largest independent set in G, and let theta(G) denote the Lovasz theta-function on G. We prove that for some c > 0, there exists an infinite family of graphs such ...
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For a graph G, let alpha(G) denote the size of the largest independent set in G, and let theta(G) denote the Lovasz theta-function on G. We prove that for some c > 0, there exists an infinite family of graphs such that theta(G) > alpha(G)n/2(c root log n), where n denotes the number of vertices in a graph. This disproves a known conjecture regarding the theta function. As part of our proof, we analyse the behavior of the chromatic number in graphs under a randomized version of graph products. This analysis extends earlier work of Linial and Vazirani, and of Berman and Schnitger, and may be of independent interest.
In Eurocrypt 1994 we proposed a a new type of cryptographic scheme, which can decode concealed images without any cryptographic computations, by placing two transparencies on top of each other and using the decoder...
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In implementation verification, we check that an implementation is correct with respect to a specification by checking whether the behaviors of a transition system that models the program's implementation correlat...
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ISBN:
(纸本)3540631410
In implementation verification, we check that an implementation is correct with respect to a specification by checking whether the behaviors of a transition system that models the program's implementation correlate with the behaviors of a transition system that models its specification. In this paper, we investigate the effect of concurrency on the complexity of implementation verification. We consider trace-based and tree-based approaches to the verification of concurrent transition systems, with and without fairness. Our results show that in almost all cases the complexity of the problem is exponentially harder than that of the sequential case. Thus, as in the model-checking verification methodology, the state-explosion problem cannot be avoided.
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