OpenRaiser/Intern-Atlas huggingface dataset:
A generalized brightness change model for computing optical flow
Authors: Shahriar Negahdaripour, Chih-Ho Yu
Venue: ICCV
Year: 1993

The authors propose an image motion constraint equation based on a model which allows the brightness of a scene point to vary with time, unlike the case in the brightness constancy model. Using this model, they describe a method for the computation of optical flow and investigate its performance in a variety of conditions involving brightness variations of scene points, due to illumination nonuniformity, light source motion, specular reflection, and/or interreflection. It is shown that in the application of this method, care must be taken in the estimation of image derivatives using finite difference methods to prevent biases in the solution. A simple modification is suggested to overcome the problem. A comparison is made with two other models, including the classical brightness constancy model, through results from experiments with real images.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Contextual feature similarities for model-based object recognition
Authors: Detlev Noll, Michael Schwarzinger, Werner von Seelen
Venue: ICCV
Year: 1993

Various feature-based object recognition methods make use of similarity measures of features to guide the recognition process. These similarity measures often are only local in nature, meaning that the measures are derived from the local attributes of the features. A similarity measure is presented that takes the form of an object based on the position of the features. A quantity that assesses the similarity of features according to their position among all others, called a context similarity measure, is derived. It is tolerant to missing features or variations in their position. The primary interest is in measuring the similarity between model features and features extracted from an image. The authors consider the use of these measures for object recognition and, as an example, describe their application in a feature-based Hough transform. They show that the combination of local and context similarities considerably improves the recognition performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
A global algorithm for shape from shading
Authors: John Oliensis, Paul Dupuis
Venue: ICCV
Year: 1993

A global algorithm for reconstructing shape from shading is described. This algorithm incorporates an earlier local algorithm that has been shown to be capable of fast, robust surface reconstruction for general surfaces if a small amount of information on the surface is provided. The new algorithm is capable of determining this information automatically, and thus can reconstruct a general surface from shading with no a priori information on the surface. In experimental tests on complex synthetic images, this algorithm has produced good surface reconstructions over most of the image. For 128 /spl times/ 128 images, the reconstruction took less than 30 s on a DECstation 5000. The algorithm appears noise resistant, giving good reconstructions even with an added pixel noise of /spl plusmn/10%.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Dynamic fixation [active vision]
Authors: Kourosh Pahlavan, Tomas Uhlin, Jan-Olof Eklundh
Venue: ICCV
Year: 1993

Fixation is the link between the observer and the events in the outside world and is a key element in the control strategy of an active vision system. The authors describe how the fixation process functions in human beings in general and discuss one of the essential components of fixation, vergence, in particular. They discuss the components of the human fixation model and through its geometry and organization describe a machine fixation model, running in real-time on a head-eye system. The authors are motivated by the need for gaze control in head-eye systems, which entails the need to clarify some fundamental relations in primate vergence movements, namely, the relations between disparity and blur and between vergence and accommodation. Following the geometry behind vergence movements, it is also suggested that the mechanism for disparity detection can use the symmetry present in the pattern of the left and right images through isolating vergence from version.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Surface discontinuities in range images
Authors: Tomás Pajdla, Václav Hlavác
Venue: ICCV
Year: 1993

The authors present a formulation of discontinuity detection in range images. The emphasis is on roof edge detection which is evaluated as C/sup 1/ discontinuity strength at every point in the range image. Contrary to other local approaches, it is possible to detect all shapes of C/sup 1/ discontinuity from one polynomial approximation even when the viewpoint changes. First, the range data are locally approximated by a second-order bivariate polynomial. Second, the 2-D problem of surface discontinuity strength estimation is converted to a 1-D probem along the direction of maximal normal curvature at each point on the surface. Third, C/sup 1/ is computed by comparing the polynomial approximation of data and the polynomial approximation of the discretized model of the discontinuity.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Accurate line parameters from an optimising Hough Transform for vanishing point detection
Authors: Phil L. Palmer, Maria Petrou, Josef Kittler
Venue: ICCV
Year: 1993

The authors show that a Hough transform algorithm can give sufficiently accurate estimates of line parameters to accurately locate vanishing points, even when they are several hundred pixels off the image. For this purpose, a 2-D robust kernel is used and the continuity of the accumulator array is exploited to optimize the parameter estimates. The algorithm is described in detail and results are shown on a variety of images, including synthetic images to determine quantitatively the accuracy of the vanishing point location by performing statistical tests.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
A linear complexity procedure for labelling line drawings of polyhedral scenes using vanishing points
Authors: Pietro Parodi, Vincent Torre
Venue: ICCV
Year: 1993

The authors investigate the computational time complexity of the labeling problem for line drawings of polyhedral scenes. It is found that line drawings can be labeled in time proportional to the number of segments once the vanishing points associated to the possible directions for the edges are known. The vanishing points can be given a priori, otherwise they can in many cases be detected by standard techniques from the line drawing itself. The NP-completeness of the labeling problem for line drawings of trihedral scenes (Kirousis and Papadimitriou, 1988) is then due to the lack of knowledge about the vanishing points, which is equivalent to the knowledge of the possible directions for the edges. These results help draw a more accurate boundary between the problems in the interpretation of line drawings that are polynomially solvable and those that are NP-complete.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Learning object recognition models from images
Authors: Arthur R. Pope, David G. Lowe
Venue: ICCV
Year: 1993

To recognize an object in an image an internal model is required to indicate how that object may appear. The authors show how to learn such a model from a series of training images depicting a class of objects, producing a model that represents a probability distribution over the variation in object appearance. Features identified in an image through perceptual organization are represented by a graph whose nodes include feature labels and numeric measurements. A learning procedure generalizes multiple image graphs to form a model graph in which the numeric measurements are characterized by probability distributions. A matching procedure, using a similarity metric based on a non-parametric probability density estimator, compares model and image graphs to identify an instance of a modeled object in an image. Experimental results are presented from a system constructed to test this approach. The system learns to recognize partially occluded 2-D objects in 2-D images using shape cues. It can recognize objects as similar in general appearance while distinguishing them by their detailed features. >
Recognition of object classes from range data
Authors: Ian D. Reid 0001, J. Michael Brady
Venue: ICCV
Year: 1993

The authors present techniques for recognizing instances of 3-D object classes from sets of 3-D feature observations. Recognition of a class instance is structured as a search of an interpretation tree in which geometric constraints on pairs of sensed features not only prune the tree, but are used to determine upper and lower bounds on the model parameter values of the instance. A real-valued constraint propagation network unifies the representations of the model parameters, model constraints and feature constraints, and provides a simple and effective mechanism for accessing and updating parameter values. Recognition of objects with multiple internal degrees of freedom, including non-uniform scaling and stretching, articulations, and subpart repetitions, is demonstrated for two different types of real range data: 3-D edge fragments from a stereo vision system, and position/surface normal data derived from planar patches extracted from a range image.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Tracking foveated corner clusters using affine structure
Authors: Ian D. Reid 0001, David William Murray 0001
Venue: ICCV
Year: 1993

The authors describe a novel method of obtaining a fixation point on a moving object for a real-time gaze control system. The method makes use of a real-time implementation of a corner detector and tracker and reconstructs the image position of the desired fixation point from a cluster of corners detected on the object using the affine structure available from two or three views. The method is fast, reliable, viewpoint invariant, and insensitive to occlusion and/or individual corner dropout or reappearance. Results are presented for the method used with a high performance head/eye platform. The results are compared with two naive fixation methods.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Occam algorithms for computing visual motion
Authors: Haim Schweitzer
Venue: ICCV
Year: 1993

By drawing an analogy with machine learning, the author proposes to define visual motion as a predictor that can accurately predict future frames. Under this new definition, visual motion can be specified by a collection of image patches, each moving in a simple motion. An implementation with rectangular patches determined recursively by a binary decision tree is described. Experimental results on real video sequences verify the algorithm assumptions and show that motion in typical sequences can be accurately described in terms of a few parameters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
A modal framework for correspondence and description
Authors: Stan Sclaroff, Alex Pentland
Venue: ICCV
Year: 1993

The authors describe a framework for establishing correspondence, computing canonical descriptions, and recognizing objects that is based on the idea of describing objects by their generalized symmetries, as defined by the object's free vibration modes. A technique given by A. Pentland and S. Scarloff (1991) described objects in terms of the modes of some prototype shape. In contrast, this new method computes the object's modes directly from available image information. This results in greater generality and accuracy, and is applicable to data of any dimensionality. For the purposes of illustration, a detailed mathematical formulation of the method is given for 2-D problems, and it is demonstrated on gray-scale image and contour data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Robust line-based pose enumeration from a single image
Authors: Takeshi Shakunaga
Venue: ICCV
Year: 1993

The authors propose robust algorithms for line-based pose enumeration from a single view and report on their evaluations by simulations. The proposed algorithms incorporate two major refinements into the algorithms originally proposed by T. Shakunaga. The first refinement, introduction of zone-crossing detection to the 1-D search, decreases the rate of overlooking a correct pose. The second refinement, adaptive selection of a perspective angle transform pair, considerably reduces the average estimation error. Simulation results show that pose estimation precision depends primarily on the precision of line detection. Although the refinements are effective, they are better for more precise line detection. For 99% of rigid body samples, the algorithm can estimate rotation with an error of less than 2/spl deg/, and for 99.9% of the samples, the error is less than 10/spl deg/. Simulation experiments for articulated objects show similar results by using the second algorithm.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Projective depth: A geometric invariant for 3D reconstruction from two perspective/orthographic views and for visual recognition
Authors: Amnon Shashua
Venue: ICCV
Year: 1993

The author addresses the problems of reconstructing 3-D space in a projective framework from two views and of artificially generating novel views of the scene from two given views. It is shown that with the correspondences coming from four non-coplanar points in the scene and the corresponding epipoles, it is possible to define and reconstruct a projective invariant, referred to as projective depth, that can be used later to reconstruct the projective or affine structure of the scene or directly to generate novel views of the scene. The derivation has the advantage that the viewing transformation matrix need not be recovered in the course of computations. >
Experiments with monocular visual tracking and environment modeling
Authors: Olli Silvén, Tapio Repo
Venue: ICCV
Year: 1993

The purpose has been to find solutions for reliable real-time monocular visual tracking and simultaneous environment modeling. The goal is to estimate the relative motion of a camera with respect to a rigid scene by tracking features such as corners and lines. In the beginning, the 3-D locations of the features are not known accurately, but during the tracking process the model errors are reduced through the integration of new observations. The focus is on modeling measurement uncertainties and selecting the features to be extracted from image frames. Experiments have been performed by using a bank of trackers, each of which calculates estimates for location and motion using measurements of a few features at a time.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Incremental image sequence enhancement with implicit motion compensation
Authors: Ajit Singh
Venue: ICCV
Year: 1993

The author describes a recursive technique to enhance image-sequences. This technique has the effect of motion-compensated temporal smoothings. It suppresses noise but does not blur the moving regions. The method does not require that the motion-field be explicitly computed in advance. Instead it incorporates an implicit model for temporal rate of change of intensity. Based on this model, the technique computes the optimal estimate of the instantaneous image intensity in an incremental fashion. The estimate improves over time. Experimental results are shown on image-sequences from various application domains.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Recovering reflectance and illumination in a world of painted polyhedra
Authors: Pawan Sinha, Edward H. Adelson
Venue: ICCV
Year: 1993

To be immune to variations in illumination, a vision system needs to be able to decompose images into their illumination and surface reflectance components. Most computational studies thus far have been concerned with strategies for solving the problem in the restricted domain of 2-D Mondrians. This domain has the simplifying characteristic of permitting discontinuities only in the reflectance distribution while the illumination distribution is constrained to vary smoothly. Such approaches prove inadequate in a 3-D world of painted polyhedra which allows for the existence of discontinuities in both the reflectance and illumination distributions. The authors propose a two-stage computational strategy for interpreting images acquired in such a domain. The first stage attempts to use simple local gray-level junction analysis to classify the observed image edges into the illumination or reflectance categories. Subsequent processing verifies the global consistency of these local inferences while also reasoning about the 3-D structure of the object and the illumination source direction.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Ridge-detection for the perceptual organization without edges
Authors: J. Brian Subirana-Vilanova, Kah Kay Sung
Venue: ICCV
Year: 1993

The authors present a novel vector ridge detector which automatically finds the right scale of a ridge even in the presence of noise, multiple steps and narrow valleys. One of the key features of the ridge detector is that it has a zero response at discontinuities. The ridge detector can be applied both to scalar and vector quantities such as color. A parallel perceptual organization scheme that works without edges and is based on the ridge detector is also presented. In addition to perceptual groups, the scheme computes potential focus of attention points at which to direct future processing. The relation to human perception and several theoretical findings supporting the scheme are presented. Results of a Connection Machine implementation of the scheme are presented for perceptual organization using color.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Recognizing mice, vegetables and hand printed characters based on implicit polynomials, invariants and Bayesian methods
Authors: Jayashree Subrahmonia, Daniel Keren, David B. Cooper
Venue: ICCV
Year: 1993

The authors present a robust low-computational-cost system for recognizing freeform objects in 3-D range data or in 2-D curve data in the image plane. Objects are represented by implicit polynomials, i.e., 3-D algebraic surfaces or 2-D algebraic curves of degrees greater than two, and are recognized by computing and matching vectors of their algebraic invariants, which are functions of their coefficients that are invariant to translations, rotations, and general linear transformations. Implicit polynomials of fourth degree can represent complicated asymmetric free-form shapes. A design of Bayesian recognizers for these models and their invariants that results in low-computational-cost recognizers robust to noise, partial occlusion, and other perturbations of the data sets is considered. This work extends the work of D. Keren et al. (1992) by developing and using new invariants for 3-D surface polynomials and applying the Bayesian recognizer to operating on invariants.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Understanding noise: The critical role of motion error in scene reconstruction
Authors: J. Inigo Thomas, Allen R. Hanson, John Oliensis
Venue: ICCV
Year: 1993

In structure from motion algorithms, the error in the estimated motion affects each reconstructed 3-D point in a systematic way. The authors attempt to isolate the effect of the motion error as correlations in the structure error and show theoretically that these correlations can improve existing multi-frame structure from motion techniques. Experimental results and previously reported work confirm the theoretical predictions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
The reciprocal-wedge transform for space-invariant sensing
Authors: Frank Tong, Ze-Nian Li
Venue: ICCV
Year: 1993

A reciprocal-wedge transform (RWT) for space-variant sensing is presented. The RWT preserves linear features and facilitates translations in images. A concise RWT matrix representation and its applications to geometric transformations in the image plane are described. Like the log-polar transform, the RWT facilitates space-variant sensing, which enables effective use of variable-resolution data and the reduction of the total amount of sensory data. The RWT yields anisotropic variable resolution, which provides an alternative for active sensing when the shift of attention is primarily in one dimension. A projective model of the RWT is delineated and a hardware RWT projection camera is proposed. As an application of the RWT, the problem of road following in robot navigation and some initial experimental results are demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Computation of ego-motion and structure from visual and inertial sensors using the vertical cue
Authors: Thierry Viéville, Emmanuelle Clergue, P. E. Dos Santos Facao
Venue: ICCV
Year: 1993

The authors develop a method of recovery of some aspects of the 3-D structure and motion of a scene in the case of a virtual moving observer with visual and odometric sensors. This observer attempts to build a 3-D depth and kinematic map of its environment, which can obtain fixed or moving objects. The development and implementation of some layers of a line-segment based module are described to recover ego-motion while building a 3-D map of the environment in which the absolute vertical is taken into account. Given a monocular sequence of images and 2-D-line-segments in this sequence, the goal is to reduce the disparity between two frames in such a way that 3-D vision is simplified, while an initial value for the 3-D rotation is provided. Using the vertical as a basic cue for 3-D-orientation tremendously simplifies and enrichs the structure from motion paradigm, but the usual equations have to be worked out in a different way.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Robust computation of optical flow in a multi-scale differential framework
Authors: Joseph Weber, Jitendra Malik
Venue: ICCV
Year: 1993

The authors developed an algorithm for computing optical flow in a differential framework. The image sequence is first convolved with a set of linear, separable spatiotemporal filters similar to those that have been used in other early vision. The brightness constancy constraint can then be applied to each of the resulting images, giving in general, an overdetermined system of equations for the optical flow at each pixel. There are three principal sources of error: (a) stochastic due to sensor noise, (b) systematic errors in the presence of large displacements, and (c) errors due to failure of the brightness constancy model. The analysis of these errors leads to development of an algorithm based on a robust version of total least squares. Each optical flow vector computed has an associated reliability measure which can be used in subsequent processing. The performance of the algorithm on the data set used by J. Barron et al. (1992) compares favorably with other techniques. In addition to being separable, the filters used are also causal, incorporating only past time frames. The algorithm is fully parallel and has been implemented on a multipleprocessor machine.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>