Multiview stereo via volumetric Graph-Cuts and occlusion robust photo-consistency

This paper presents a volumetric formulation for the multi-view stereo problem which is amenable to a computationally tractable global optimisation using Graph-cuts. Our approach is to seek the optimal partitioning of 3D space into two regions labelled as "object" and "empty" under a cost functional consisting of the following two terms: (1) A term that forces the boundary between the two regions to pass through photo-consistent locations and (2) a ballooning term that inflates the "object" region. To take account of the effect of occlusion on the first term we use an occlusion robust photo-consistency metric based on Normalised Cross Correlation, which does not assume any geometric knowledge about the reconstructed object. The globally optimal 3D partitioning can be obtained as the minimum cut solution of a weighted graph.     

Corrected ISICSoo class version

The Coster–Kronig enhancement factor calculation for _M3$M_3$ shell x-ray production cross sections was found to be incorrect in both ISICSoo class (Bati? et al. (2012) [1]) and isics program (Cipolla (2013) [2]). The affected functions of ISICSoo class have been corrected. The resulting X-ray production cross sections are modified by less than 15%, while ionization cross sections are unchanged.     

A Decision Procedure for a Sublanguage of Set Theory Involving Monotone, Additive, and Multiplicative Functions

MLSS is a decidable sublanguage of set theory involving the predicates membership, set equality, set inclusion, and the operators union, intersection, set difference, and singleton.In this paper we extend MLSS with constructs for expressing monotonicity, additivity, and multiplicativity properties of set-to-set functions. We prove that the resulting language is decidable by reducing the problem of determining the satisfiability of its sentences to the problem of determining the satisfiability of sentences of MLSS.     

A Decision Procedure for a Sublanguage of Set Theory Involving Monotone, Additive, and Multiplicative Functions, I: The Two-Level Case

2LS is a decidable many-sorted set-theoretic language involving one sort for elements and one sort for sets of elements. In this paper we extend 2LS with constructs for expressing monotonicity, additivity, and multiplicativity properties of set-to-set functions. We call the resulting language 2LSmf. We prove that 2LSmf is decidable by reducing the problem of determining the satisfiability of its sentences to the problem of determining the satisfiability of sentences of 2LS. Furthermore, we prove that the language 2LSmf is stably infinite with respect to the sort of elements. Therefore, by using a many-sorted version of the Nelson–Oppen combination method, 2LSmf can be combined with other languages modeling the sort of elements.     

Infinite elements in the time domain using a prolate spheroidal multipole expansion

Many phenomena in acoustically loaded structural vibrations are better understood in the time domain, particularly transient radiation, shock, and problems involving non-linearities, cavitation, and bulk structural motion. In addition, the geometric complexity of structures of interest drives the analyst toward domain-discretized solution methods, such as finite elements or finite differences, and large numbers of degrees of freedom. In such methods, efficient numerical enforcement of the Sommerfeld radiation condition in the time domain becomes difficult. Although a great many methodologies for doing so have been demonstrated, there seems to exist no consensus on the optimal numerical implementation of this boundary condition in the time domain. Here, we present theoretical development of several new boundary operators for conventional finite element codes. Each proceeds from successful domain-discretized, projected field-type harmonic solutions, in contrast to boundary integral equation operators or those derived from analyses of outgoing waves. We exploit the separable prolate-spheroidal co-ordinate system, which is sufficiently general for a large variety of problems of naval interest, to obtain finite element-like operators (matrices) for the boundary points. Use of this co-ordinate system results in element matrices that can be analytically inverse transformed from the frequency to the time domain, without imposing continuity requirements on the solution above those imposed by the underlying partial differential equation. In addition, use of element-like boundary operators does not alter the banded structure of assembled system matrices. Results presented here include theoretical derivation of the infinite elements, resolution of the Fourier inversion issues, and element matrices for the boundary operators which introduce no new continuity requirements on the fluid field variable. The simplest infinite elements are verified in a coupled three-dimensional context against DAA2 and Helmholtz integral equation results. © 1998 John Wiley & Sons, Ltd.     

Visually guided grasping in unstructured environments

We present simple and robust algorithms which combine uncalibrated stereo vision and a robot manipulator to enable it locate, reach and grasp unmodelled objects in unstructured environments. In the first stage, an operator indicates the object to be grasped by simply pointing at it. Next, the vision system segments the indicated object from the background, and plans a suitable grasp strategy. Finally, the robotic arm reaches out towards the object and executes the grasp. Uncalibrated stereo vision allows the system to continue to operate in the presence of errors in the kinematics of the robot manipulator and unknown changes in the position, orientation and intrinsic parameters of the stereo cameras during operation.     

Determining the gaze of faces in images

A person's gaze is a potentially powerful input device for human-computer interaction. Current approaches to gaze tracking tend to be highly intrusive: the subject must either remain perfectly still, or wear cumbersome headgear to maintain a constant separation between the sensor and the eye. This paper describes a more flexible vision-based approach, which can estimate the direction of gaze from a single, monocular view of a face. The technique makes minimal assumptions about the structure of the face, requires lew image measurements, and produces an accurate estimate of the facial orientation, which is relatively insensitive to noise in the image and errors in the underlying assumptions. The computational requirements are insignificant, so with automatic tracking of a few facial features it is possible to produce gaze estimates at video rate.     

Camera self-calibration from unknown planar structures enforcingthe multiview constraints between collineations

In this paper, we describe an efficient method to impose the constraints existing between the collineations between images which can be computed from a sequence of views of a planar structure. These constraints are usually not taken into account by multiview techniques in order not to increase the computational complexity of the algorithms. However, imposing the constraints is very useful since it allows a reduction of geometric errors in the reprojected features and provides a consistent set of collineations which can be used for several applications such as mosaicing, reconstruction, and self-calibration. In order to show the validity of our approach, this paper focus on self-calibration from unknown planar structures proposing a method exploiting the consistent set of collineations. Our method can deal with an arbitrary number of views and an arbitrary number of planes and varying camera internal parameters. However, for simplicity, this papers will only discuss the case with one plane in several views. The results obtained with synthetic and real data are very accurate and stable even when using only few images     

Estimating the fundamental matrix via constrained least-squares: aconvex approach

In this paper, a new method for the estimation of the fundamental matrix from point correspondences in stereo vision is presented. The minimization of the algebraic error is performed while taking explicitly into account the rank-two constraint on the fundamental matrix. It is shown how this nonconvex optimization problem can be solved avoiding local minima by using recently developed convexification techniques. The obtained estimate of the fundamental matrix turns out to be more accurate than the one provided by the linear criterion, where the rank constraint of the matrix is imposed after its computation by setting the smallest singular value to zero. This suggests that the proposed estimate can be used to initialize nonlinear criteria, such as the distance to epipolar lines and the gradient criterion, in order to obtain a more accurate estimate of the fundamental matrix