849 research outputs found
3D Shape Registration
No full textegistration is the problem of bringing together two or more 3D shapes, either of the same object or of two different but similar objects. This chapter first introduces the classical Iterative Closest Point (ICP) algorithm, which represents the gold standard registration method. Current limitations of ICP are addressed and the most popular variants are described to improve the basic implementation in several ways. Challenging registration scenarios are analyzed and a taxonomy of recent and promising alternative registration techniques is introduced. Three case studies are then described with an increasing level of problem difficulty. The first case study describes a simple but effective technique to detect outliers. The second case study uses the Levenberg-Marquardt optimization procedure to solve standard pairwise registration. The third case study focuses on the challenging problem of deformable object registration. Finally, open issues and directions for future work are discussed and conclusions are drawn
3D Shape Registration
No full textRegistration is the problem of bringing together two or more 3D shapes, either of the same object or of two different but similar objects. This chapter first introduces the classical Iterative Closest Point (ICP) algorithm which represents the gold standard registration method. Current limitations of ICP are addressed, and the most popular variants of ICP are described to improve the basic implementation in several ways. Challenging registration scenarios are analyzed, and a taxonomy of recent and promising alternative registration techniques is introduced. Four case studies are then described with an increasing level of difficulty. The first case study describes a simple but effective technique to detect outliers. The second case study uses the Levenberg–Marquardt (LM) optimization procedure to solve standard pairwise registration. The third case study focuses on the challenging problem of deformable object registration. The fourth case study introduces an ICP method for preoperative data registration in laparoscopy. Finally, open issues and directions for future work are discussed, and conclusions are drawn
Semantic Shape Context for the Registration of Multiple Partial 3D Views
No full textPoint-to-point matching is a crucial stage of 3D shape analysis. It is usually solved by using descriptors that summarize the most characteristic and discriminative properties of each point. Combining local and global context information in the point descriptor is a promising approach. We propose a new approach based on what we call semantic shape context to combineeffectively local descriptors and global context information by exploiting the Bag of Words (BoW) paradigm for the representation of a single 3D point. Several local pointdescriptors are collected and quantized from the training set, by defining the visual vocabulary composed by a fixed number of visual words. Each point is then represented by a set of BoWs which encode the inter-relationship with all the other points of the object (i.e., the context). Experiments were carried out on several 3D models. The proposed approach makes fully automatic 3D registration of partial views possible, and generally outperforms stateof-the-art methods in terms of robustness and accuracy
DEFORM'06 - Proceedings of the Workshop on Image Registration in Deformable Environments
No full textPreface These are the proceedings of DEFORM'06, the Workshop on Image Registration in Deformable Environments, associated to BMVC'06, the 17th British Machine Vision Conference, held in Edinburgh, UK, in September 2006. The goal of DEFORM'06 was to bring together people from different domains having interests in deformable image registration. In response to our Call for Papers, we received 17 submissions and selected 8 for oral presentation at the workshop. In addition to the regular papers, Andrew Fitzgibbon from Microsoft Research Cambridge gave an invited talk at the workshop. The conference website including online proceedings remains open, see http://comsee.univ-bpclermont.fr/events/DEFORM06. We would like to thank the BMVC'06 co-chairs, Mike Chantler, Manuel Trucco and especially Bob Fisher for is great help in the local arrangements, Andrew Fitzgibbon, and the Programme Committee members who provided insightful reviews of the submitted papers. Special thanks go to Marc Richetin, head of the CNRS Research Federation TIMS, which sponsored the workshop. August 2006 Adrien Bartoli Nassir Navab Vincent Lepeti
DEFORM'06 - Proceedings of the Workshop on Image Registration in Deformable Environments
No full textPreface These are the proceedings of DEFORM'06, the Workshop on Image Registration in Deformable Environments, associated to BMVC'06, the 17th British Machine Vision Conference, held in Edinburgh, UK, in September 2006. The goal of DEFORM'06 was to bring together people from different domains having interests in deformable image registration. In response to our Call for Papers, we received 17 submissions and selected 8 for oral presentation at the workshop. In addition to the regular papers, Andrew Fitzgibbon from Microsoft Research Cambridge gave an invited talk at the workshop. The conference website including online proceedings remains open, see http://comsee.univ-bpclermont.fr/events/DEFORM06. We would like to thank the BMVC'06 co-chairs, Mike Chantler, Manuel Trucco and especially Bob Fisher for is great help in the local arrangements, Andrew Fitzgibbon, and the Programme Committee members who provided insightful reviews of the submitted papers. Special thanks go to Marc Richetin, head of the CNRS Research Federation TIMS, which sponsored the workshop. August 2006 Adrien Bartoli Nassir Navab Vincent Lepeti
Monocular template-based 3D reconstruction of extensible surfaces with local linear elasticity
No full textWe propose a new approach for template-based extensible surface reconstruction from a single view. We extend the method of isometric surface reconstruction and more recent work on conformal surface reconstruction. Our approach relies on the minimization of a proposed stretching energy formalized with respect to the Poisson ratio parameter of the surface. We derive a patch-based formulation of this stretching energy by assuming local linear elasticity. This formulation unifies geometrical and mechanical constraints in a single energy term. We prevent local scale ambiguities by imposing a set of fixed boundary 3D points. We experimentally prove the sufficiency of this set of boundary points and demonstrate the effectiveness of our approach on different developable and non-developable surfaces with a wide range of extensibility.Abed Malti, Richard Hartley, Adrien Bartoli, Jae-Hak Ki
Efficiency in Real-time Webcam Gaze Tracking
No full textEfficiency and ease of use are essential for practical applications of camera based eye/gaze-tracking. Gaze tracking involves estimating where a person is looking on a screen based on face images from a computer-facing camera. In this paper we investigate two complementary forms of efficiency in gaze tracking: 1. The computational efficiency of the system which is dominated by the inference speed of a CNN predicting gaze-vectors; 2. The usability efficiency which is determined by the tediousness of the mandatory calibration of the gaze-vector to a computer screen. To do so, we evaluate the computational speed/accuracy trade-off for the CNN and the calibration effort/accuracy trade-off for screen calibration. For the CNN, we evaluate the full face, two-eyes, and single eye input. For screen calibration, we measure the number of calibration points needed and evaluate three types of calibration: 1. pure geometry, 2. pure machine learning, and 3. hybrid geometric regression. Results suggest that a single eye input and geometric regression calibration achieve the best trade-off.Pattern Recognition and Bioinformatic
Guest Editorial: Special Issue on Traditional Computer Vision in the Age of Deep Learning
No full textTracking by detection for interactive image augmentation in laparoscopy
No full textWe present a system for marking, tracking and visually augmenting a deformable surgical site by the robust automatic detection of natural landmarks (image features) in laparoscopic surgery. In our system, the surgeon first selects a frame containing an organ of interest, and this is used by our system both to detect every instance of the organ in a laparoscopic video feed, and to recover the nonrigid deformations. The system then augments the video with customizable visual information such as the location of hidden or weakly visible structures (cysts, vessels, etc), or planned incision points, acquired from pre-operative or intra-operative data. Frame-rate organ detection is performed via a novel procedure that matches the current frame to the reference frame. Because laparoscopic images are known to be extremely difficult to match, we propose to use Shape-from-Shading and conformal flattening to cancel out much of the variation in appearance due to perspective foreshortening, and we then apply robust matching to the flattened surfaces. Experiments show robust tracking and detection results on a laparoscopic procedure with the uterus as target organ. As our system detects the organ in every frame, it is not impaired by target loss, contrary to most previous methods.Jae-Hak Kim, Adrien Bartoli, Toby Collins, and Richard Hartle
Law & Economics Perspectives on Electricity Regulation
No full textThis paper first reviews some of the main contributions of the new institutional economics to the analysis of the process of competitive transformation of network industries. It shows that neoinstitutional analysis is complementary to the microeconomics of rational pricing, since it accounts for the decisive role of an institutional framework adapted to new transactions. It emphasizes the importance of the political reform process, which draws on the conditions of attractiveness and feasibility to define an initial reorganization of property rights in these industries. The paper then analyzes in this light some of the main challenges ahead for electricity regulation: the question of investment in generation capacities and the link to long term contracts, the regulation of wholesale market power, the support to Renewable Energy Sources for Electricity (RES-E) and the design of new regulatory authorities.Electricity Markets; New Institutional Economics; Law & Economics
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