1993 (4th) International Conference on Computer Vision

Superquadric is an implicit model which was recently introduced and successfully applied in computer vision research. The authors introduce its generalization, the use of the hyperquadric models, for computer vision applications, and focus on its utilization for shape recovery from range data. The hyperquadric model can be composed of any number of terms. Its geometric bound is an arbitrary convex... View full abstract»

The term visual echoes is introduced as a common framework for the analysis of multi-frame optical flow, binocular and trinocular stereo, stationary texture and boundary symmetries. The authors examined cepstral filtering, a powerful nonlinear adaptive technique for the retrieval of echoes, as a common methodology to address these visual routines. They consider the application of cepstral analysis... View full abstract»

A method for localization, the act of recognizing the environment, is presented. The method is based on representing the scene as a set of 2-D views and predicting the appearances of novel views by linear combinations of the model views. The method accurately approximates the appearance of scenes under weak perspective projection. Analysis of this projection as well as experimental results demonst... View full abstract»

The authors consider the problem of robustly estimating optical flow from a pair of images using a new framework based on robust estimation which addresses violations of the brightness constancy and spatial smoothness assumptions. They also show the relationship between the robust estimation framework and line-process approaches for coping with spatial discontinuities. In doing so, the notion of a... View full abstract»

A design that builds on well-known schemes using gratings is outlined. The key development here is the use of commutation as a means of modulating the grating output signal. This enables backwards and forwards motion to be distinguished. Results from an analog implementation of the visual motion transducer are presented. The current transducer measures translational motion across the grating. The ... View full abstract»

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 an... View full abstract»

The authors describe a technique for building compact models of the shape and appearance of flexible objects seen in 2-D images. The models are derived from the statistics of sets of labeled images of example objects. Each model consists of a flexible shape template, describing how important points of the object can vary, and a statistical model of the expected grey levels in regions around each m... View full abstract»

An automatic ego motion compensation based feature detection and correspondence algorithm is presented. For image sequences taken from a moving camera, feature displacement over consecutive frames can be approximately decomposed into two components: the displacement due to camera motion, which can be compensated for by image rotation, scaling, and translation; and the displacement due to object mo... View full abstract»

The author presents new deformable spline surfaces for segmentation of 3-D medical images. He explores parametric surfaces with two different topologies, planar and cylindrical, that permit segmentation of fine anatomical structures. The surface deformation process is seen as a sequence of least squares approximations of dense data. When the deformation process stops, a smooth differentiable surfa... View full abstract»

The authors present a methodology for designing experiments to characterize detection algorithms. The usual method is to vary parameters of the input images or parameters of the algorithms and then construct operating curves that relate the probability of misdetection and false alarm for each parameter setting. Such an analysis does not integrate the performance of the numerous operating curves. A... View full abstract»

A family of qualitative methods is described that determines structure of curves in a scene from their image projections in two or more views. For example, plane curves are distinguished from space curves, and space curves from contour generators. The novelty of the approach is that first, it is unaffected by camera intrinsic parameters, so calibration is not required; second, it is also unaffecte... View full abstract»

The author describes a new method to improve the algebraic surface fitting process by better approximating the Euclidean distance from a point to the surface. In the past they have used a simple first order approximation of the Euclidean distance from a point to an implicit curve or surface which yielded good results in the case of unconstrained algebraic curves or surfaces, and reasonable results... View full abstract»

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 dept... View full abstract»

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... View full abstract»

A framework for visual tracking of contours is presented, based on a synthesis of elastic models, stochastic filtering, and geometric invariance. Flexibly coupled curve templates implement soft prior assumptions about shape. Affine invariance, built into the flexible coupling, ensures that the affine deformations that arise naturally from image projection are favored. The stochastic basis of the f... View full abstract»

The authors describe a model-based method for tracking nonrigid objects moving in a complex scene. The method operates by extracting two-dimensional models of an object from a sequence of images. The basic idea underlying the technique is to decompose the image of a solid object moving in space into two components: a two-dimensional motion and a two-dimensional shape change. The motion component i... View full abstract»

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... View full abstract»

The authors consider multiscale Markov random field (MRF) models. It is well known that multigrid methods can improve significantly the convergence rate and the quality of the final results of iterative relaxation techniques. A hierarchical model is proposed, which consists of a label pyramid and a whole observation field. The parameters of the coarse grid can be derived by simple computation from... View full abstract»

Relative depth information can be obtained using extremely fine vergence movements called vergence micromovements about the fixation point with almost no computation and without knowledge of camera parameters. The vergence micromovements approach uses a continuous vergence angle control with simultaneous computation of the local correspondence response of elements with the same relative position i... View full abstract»

The generic view assumption states that an observer is not in a special position relative to the scene. The author shows how to use the generic view assumption to quantify the likelihood of a view and so derive a powerful tool to estimate scene parameters. Generic variables can include viewpoint, object orientation, and lighting position. By considering the image as a function of these variables, ... View full abstract»

The authors present the theory of probabilistic relaxation for matching symbolic structures, derive as limiting cases the various heuristic formulas used by researchers in matching problems, and state the conditions under which they apply. They successfully apply the theory to the problem of matching and recognizing aerial road network images based on road network models and to the problem of edge... View full abstract»

A framework called Cresceptron is introduced for automatic algorithm design through learning of concepts and rules, thus deviating from the traditional mode in which humans specify the rules constituting a vision algorithm. With the Cresceptron, humans as designers need only to provide a good structure for learning, but they are relieved of most design details. The Cresceptron has been tested on t... View full abstract»

A new model, Frenet-Serret motion, is proposed for the motion of an observer in a stationary environment. This model relates the motion parameters of the observer to the curvature and torsion of the path along which the observer moves. Screw-motion equations for Frenet-Serret motion are derived and employed for geometrical analysis of the motion. Normal flow is used to derive constraints on the ro... View full abstract»

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 re... View full abstract»