OpenRaiser/Intern-Atlas huggingface dataset:
Motion Analysis with a Camera with Unknown, and Possibly Varying Intrinsic Parameters
Authors: Thierry Viéville, Olivier D. Faugeras
Venue: ICCV
Year: 1995

In the present paper we address the problem of computing structure and motion, given a set point correspondences in a monocular image sequence, considering small motions when the camera is not calibrated. We first set the equations defining the calibration, rigid motion and scene structure. We then review the motion equation, the structure from equation and the depth evolution equation, including the particular case of planar structures, considering a discrete displacement between two frames. A step further, we develop the first order expansion of these equations and analyse the observability of the related infinitesimal quantities. It is shown that we obtain a complete correspondence between these equations and the equation derived in the discrete case. However, in the case of infinitesimal displacements, the projection of the translation (focus of expansion or epipole) is clearly separated from the rotational component of the motion. This is an important advantage of the present approach. Using this last property, we propose a mechanism of image stabilization in which the rotational disparity is iteratively canceled. This allows a better estimation of the focus of expansion, and simplifies different aspects of the analysis of the equations: structure from motion equation, analysis of ambiguity, geometrical interpretation of the motion equation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Invariant-Based Recognition of Complex Curved 3D Objects from Image Contours
Authors: B. Vijayakumar, David J. Kriegman, Jean Ponce
Venue: ICCV
Year: 1995

To recognize three-dimensional objects bounded by smooth curved surfaces from monocular image contours, viewpoint-dependent image features must be related to object geometry. Contour bitangents and inflections along with associated parallel tangents points are the projection of surface points that lie on the occluding contour for a five-parameter family of scaled orthographic projection viewpoints. An invariant representation can be computed from these image features and seen for modeling and recognizing objects. Modeling is achieved by moving an object in front of a camera to obtain a curve of possible invariants. The relative camera-object motion is not required, and 3D models are not utilized. At recognition time, invariants computed from a single image are used to index the model database. Using the matched features, independent qualitative and quantitative verification procedures eliminate potential false matches. Examples from an implementation are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Shape from Shading with Interreflections under Proximal Light Source: 3D Shape Reconstruction of Unfolded Book Surface from a Scanner Image
Authors: Toshikazu Wada, Hiroyuki Ukida, Takashi Matsuyama
Venue: ICCV
Year: 1995

We address the problem to recover the 3D shape of an unfolded book surface from the shading information in a scanner image. From a technical point of view, this shape from shading problem in real world environments is characterized by (1) proximal light source, (2) interreflections, (3) moving light source, (4) specular reflection, and (5) nonuniform albedo distribution. Taking all these factors into account, we first formulate the problem based on an iterative nonlinear optimization scheme. Then we introduce piecewise polynomial models of the 3D shape. Image restoration experiments for a real book surface demonstrated that geometric and photometric distortions are almost completely removed by the proposed method.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Region Correspondence by Inexact Attributed Planar Graph Matching
Authors: Caihua Wang, Keiichi Abe
Venue: ICCV
Year: 1995

An efficient graph matching approach is proposed for finding region correspondence between two images of the same scene but taken from different viewpoints. Regions and their relations in an image are represented with region adjacency graph (RAG), which is a kind of attributed planar graph. The problem to find an optimal region correspondence, which matches the regions in two images with maximal similarity in region features and region relations, is formulated into the problem to find the optimal inexact matching between two RAGs. The properties specific to planar graph and that of the region adjacency relations are utilized to invent an efficient algorithm to solve the problem. Experimental results on various kinds of images show the effectiveness of the method.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Rigid Body Segmentation and Shape Description from Dense Optical Flow under Weak Perspective
Authors: Joseph Weber, Jitendra Malik
Venue: ICCV
Year: 1995

We present an algorithm for identifying and tracking independently moving rigid objects from optical flow. The proposed method uses the fact that each distinct object has a unique epipolar constraint associated with its motion. This is in contrast to using local optical flow information for segmentation. Thus motion discontinuities based on self-occlusion are distinguished from those due to separate objects. The use of epipolar geometry allows for the determination of individual motion parameters for each object as well as the recovery of relative depth for each point on the object. The segmentation problem is formulated as a scene partitioning problem and a statistic-based algorithm which uses only nearest neighbor interactions and a finite number of iterations is developed. A Kalman filter based approach is used for tracking motion parameters with time. The algorithm assumes an affine camera where perspective effects are limited to changes in overall scale. No camera calibration parameters are required.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
The Study of 3D-from-2D Using Elimination
Authors: Michael Werman, Amnon Shashua
Venue: ICCV
Year: 1995

The paper unifies most of the current literature on 3D geometric invariants from point correspondences across multiple 2D views by using the tool of elimination from algebraic geometry. The technique allows one to predict results by counting parameters and reduces many complicated results obtained in the past (reconstructuon from two and three views, epipolar geometry from seven points, trilinearity of three views, the use of a priori 3D information such as bilateral symmetry, shading and color constancy, and more) into a few lines of reasoning each. The tool of Grobner base computation is used in the elimination process. In the process we obtain several results on N view geometry, and obtain a general result on invariant functions of 4 views and its corresponding quadlinear tensor: 4 views admit minimal sets of 16 invariant functions (of quadlinear forms) with 81 distinct coefficients that can be solved linearly from 6 corresponding points across 4 views. This result has non trivial implications to the understanding of N view geometry. We show a new result on single view invariants based on 6 points and show that certain relationships are impossible. One of the appealing features of the elimination approach is that it is simple to apply and does not require any understanding of the underlying 3D from 2D geometry and algebra.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Closing the Loop on Multiple Motions
Authors: Charles Wiles, Michael Brady 0001
Venue: ICCV
Year: 1995

We describe a number of advances in the analysis of road scenes when the scene contains multiple moving objects and is observed by a single nonsteerable camera mounted on the front of a vehicle. Our structure from motion approach to scene segmentation derives front the observed motions of independently moving objects and requires no prior knowledge. We describe a hierarchy of camera models for the analysis of the scene, the simpler models handle degeneracies that occur in the more complex models. The major technical contribution is the recursive computation of feature clusters, which are fed forward over time. This closed loop feature tracking generates extended feature trajectories which significantly improve the discriminating power of scene segmentation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
A Quantitative Analysis of View Degeneracy and its use for Active Focal Length control
Authors: David Wilkes, Sven J. Dickinson, John K. Tsotsos
Venue: ICCV
Year: 1995

We quantify the observation by Kender and Freudenstein (1987) that degenerate views occupy a significant fraction of the viewing sphere surrounding an object. This demonstrates that systems for recognition must explicitly account for the possibility of view degeneracy. We show that view degeneracy cannot be detected from a single camera viewpoint. As a result, systems designed to recognize objects from a single arbitrary viewpoint must be able to function in spite of possible undetected degeneracies, or else operate with imaging parameters that cause acceptably low probabilities of degeneracy. To address this need, we give a prescription for active control of focal length that allows a principled tradeoff between the camera field of view and probability of view degeneracy.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Stochastic Completion Fields: A Neural Model of Illusory Contour Shape and Salience
Authors: Lance R. Williams, David W. Jacobs
Venue: ICCV
Year: 1995

We describe an algorithm and representation level theory of illusory contour shape and salience. Unlike previous theories, our model is derived from a single assumption-namely, that the prior probability distribution of boundary completion shape can be modeled by a random walk in a lattice whose points are positions and orientations in the image plane (i.e. the space which one can reasonably assume is represented by neurons of the mammalian visual cortex). Our model does not employ numerical relaxation or other explicit minimization, but instead relies on the fact that the probability that a particle following a random walk will pass through a given position and orientation on a path joining two boundary fragments can be computed directly as the product of two vector-field convolutions. We show that for the random walk we define, the maximum likelihood paths are curves of least energy, that is, on average, random walks follow paths commonly assumed to model the shape of illusory contours. A computer model is demonstrated on numerous illusory contour stimuli from the literature.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Gabor Wavelets for 3-D Object Recognition
Authors: Xing Wu, Bir Bhanu
Venue: ICCV
Year: 1995

This paper presents a model-based object recognition approach that uses a hierarchical Gabor wavelet representation. The key idea is to use magnitude, phase and frequency measures of Gabor wavelet representation in an innovative flexible matching approach that can provide robust recognition. A Gabor grid a topology-preserving map, efficiently encodes both signal energy and structural information of an object in a sparse multi-resolution representation. The Gabor grid subsamples the Gabor wavelet decomposition of an object model and is deformed to allow the indexed object model match with the image data. Flexible matching between the model and the image minimizes a cost function based on local similarity and geometric distortion of the Gabor grid. Grid erosion and repairing is performed whenever a collapsed grid, due to object occlusion, is detected. The results on infrared imagery are presented. Where objects undergo rotation, translation, scale, occlusion and aspect variations under changing environmental conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Hypergeometric Filters for Optical Flow and Affine Matching
Authors: Yalin Xiong, Steven A. Shafer
Venue: ICCV
Year: 1995

This paper proposes new "hypergeometric" filters for the problem of image matching under the translational and affine model. This new set of filters has the following advantages: (1) High-precision registration of two images under the translational and affine model. Because the window effects are eliminated, we are able to achieve superb performance in both translational and affine matching. (2) Affine matching without exhaustive search or image warping. Due to the recursiveness of the filters in the spatial domain, we are able to analytically express the relation between filter outputs and the six affine parameters. This analytical relation enables us to directly compute these affine parameters. (3) Generality. The approach we demonstrate here can be applied to a broad class of matching problems, as long as the transformation between the two image patches can be mathematically represented in the frequency domain.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Estimating Motion and Structure from Correspondences of Line Segments between Two Perspective Images
Authors: Zhengyou Zhang
Venue: ICCV
Year: 1995

Presents an algorithm for determining 3D motion and structure from correspondences of line segments between two perspective images. To our knowledge, the paper is the first investigation of use of line segments in motion and structure from motion. Classical methods use their geometric abstraction, namely straight lines, but then three images are necessary for the motion and structure determination process. We show that two views are in general sufficient when we use line segments. The assumption we use is that two matched line segments contain the projection of a common part of the corresponding line segment in space. Indeed this is what we use to match line segments between different views. Both synthetic and real data have been used to test the proposed algorithm, and excellent results have been obtained with real data containing a relatively large set of line segments. The results are comparable with those obtained using stereo calibration.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Shape and Model from Specular Motion
Authors: Jiang Yu Zheng, Yoshihiro Fukagawa, Norihiro Abe
Venue: ICCV
Year: 1995

This work investigates visual characteristics of specular surfaces during rotation, and gives approaches to qualitatively identify and quantitatively recover shapes of these surfaces. Continuous images are taken when an object rotates. We look at specularly reflected patterns on the surfaces and their motion in the EPIs parallel to the rotation plane, from which estimation of each surface point and construction of the object model are carried out. We find very simple and direct methods to fulfill this objective; linear equations for multiple lights illumination, and a 1st-order differential equation for single light illumination. The motion of specular reflection has nice global characteristics in EPI. The surface types range from very shiny metal surfaces to surfaces with only week specular reflectance. We give both simulation and experiments on real objects.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Region Competition: Unifying Snakes, Region Growing, Energy/Bayes/MDL for Multi-band Image Segmentation
Authors: Song Chun Zhu, Tai Sing Lee, Alan L. Yuille
Venue: ICCV
Year: 1995

We present a novel statistical and variational approach to image segmentation based on a new algorithm named region competition. This algorithm is derived by minimizing a generalized Bayes/MDL (Minimum Description Length) criterion using the variational principle. We show that existing techniques in early vision such as, snake/balloon models, region growing, and Bayes/MDL are addressing different aspects of the same problem and they can be unified within a common statistical framework which combines their advantages. We analyze how to optimize the precision of the resulting boundary location by studying the statistical properties of the region competition algorithm and discuss what are good initial conditions for the algorithm. Our method is generalized to color and texture segmentation and is demonstrated on grey level images, color images and texture images.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
FORMS: A Flexible Object Recognition and Modelling System
Authors: Song Chun Zhu, Alan L. Yuille
Venue: ICCV
Year: 1995

We briefly describe a generic statistical framework for representing the shapes of animate objects using principal component analysis and stochastic shape grammars. Such a representation scheme gives a formalism for solving the inverse problem-object recognition. Then we show: how these representations can be extracted from 2D silhouettes by a novel method for skeleton extraction and shape segmentation; how a similarity metric can be defined on this shape space; and how we can perform recognition in a bottom up/top down loop. The system is demonstrated to be stable in the presence of noise, the absence of parts, the presence of additional parts, and considerable variations in articulation and viewpoint. Successful categorization is demonstrated on a dataset of seventeen categories of animate objects.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Self-calibrating a Stereo Head: An Error Analysis in the Neighbourhood of Degenerate Configurations
Authors: Lourdes de Agapito, Du Q. Huynh, Michael J. Brooks
Venue: ICCV
Year: 1998

We show that the self-calibration of a stereo head corresponding points in an image pair is in certain circumstances prone to considerable error. A novel error analysis reveals that the automated determination of relative orientation and focal length is adversely affected when the cameras verge inwards a similar amount, and when the principal point locations have a horizontal error. This analysis is facilitated by the adoption of closed-form solutions for self-calibration from previous work of the authors. It is also shown that estimation of the fundamental matrix associated with a stereo head image pair is improved when a domain-specific parameterisation and associated computational techniques are adopted. Experiments conducted with such image pairs suggest that, given cognisance of sensitive configurations and adoption of the revised method of fundamental matrix estimation, robust reconstructions are attainable. This is demonstrated on the problem of metrically reconstructing a scene from two pairs of images obtained by an uncalibrated stereo head undergoing unknown ground-plane motion.
Segmentation of Range Data into Rigid Subsets Using Surface Patches
Authors: Anthony Ashbrook, Robert B. Fisher
Venue: ICCV
Year: 1998

In this paper we consider one aspect of the problem of automatically constructing geometric models of articulated objects from multiple range images. Automatic model construction has been investigated for rigid objects, but the techniques used do nor extend easily to the articulated case. The problem arises because of the need to register surface measurements taken from different viewpoints into a common reference frame. Registration algorithms generally assume that an object does not change shape from one view to the next, but when automatically building a model of an articulated object, it is necessary for the modes of articulation to be present in the example data. To avoid this problem we propose that raw surface data of articulated objects is first segmented into rigid subsets, corresponding to rigid subcomponents of the object. This allows a model of each subcomponent to be constructed using the conventional approaches and a final, articulated model to be constructed by assembling each of the subcomponent models. We describe an algorithm developed to segment range data into rigid subsets based on surface patch correspondences and present some results for the planar patch case.
Resolution-Appropriate Shape Representation
Authors: Bernard Baldwin, Davi Geiger, Robert A. Hummel
Venue: ICCV
Year: 1998

We present a new type of "snake" in which the dimensionality of the shapes is scaled appropriately for the resolution of the images in which the shapes are embedded. We define shapes as an ordered list of control points and compute the principal components of the shapes in a prior training set. Our energy function is based upon the Mahalanobis distance of a given shape from the mean shape and on the Mahalanobis distance of the image attributes from image attribute values extracted from the training set. We show that the derivative of this energy function with respect to the modal weights is reduced as the image resolution is reduced, and that the derivative of the energy scales with the variance associated with each mode. We exploit this property to determine the subset of the modes which are relevant at a particular level of image resolution thereby reducing the dimensionality of the shapes. We implement a coarse-to-fine search procedure in the image and shape domains simultaneously, and demonstrate this procedure on the identification of anatomic structures in Computed Tomography images.
Contagion-Based Image Segmentation and Labeling
Authors: Amit Banerjee, Philippe Burlina, Fady Alajaji
Venue: ICCV
Year: 1998

We propose a segmentation method based on Polya's urn model for contagious phenomena. Initial labeling of the pixel is obtained using a Maximum Likelihood (ML) estimate or the Nearest Mean Classifier (NMC), which are used to determine the initial composition of an urn representing the pixel. The resulting urns are then subjected to a modified urn sampling scheme mimicking the development of an infection to yield a segmentation of the image into homogeneous regions. Examples of the application of this scheme to the segmentation of synthetic texture images, Ultra-Wideband Synthetic Aperture Radar (UWB SAR) images and Magnetic Resonance Images (MRI) are provided.
Separability of Pose and Expression in Facial Tracing and Animation
Authors: Benedicte Bascle, Andrew Blake 0001
Venue: ICCV
Year: 1998

We explore the application of facial tracking to automated re-animation. To this end, it is necessary to recover both head-pose and facial expression from the facial movement of a performer. However, both effects are coupled. This is a serious problem, which previous studies haven't fully considered. The solution to this interaction problem proposed here is to solve explicitly, at each timestep, for pose and expression variables. In principle this is a nonlinear inverse problem. However, appropriate parameterisation of pose in terms of affine transformations with parallax, and of expression in terms of key-frames, reduces the problem to a bilinear one. This can then be solved directly by Singular Value Decomposition. Thus actor-driven animation has ben implemented in real-time, at video field-rate, using two Indy desktop workstations.