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2009


Ball Joints for Marker-less Human Motion Capture
Ball Joints for Marker-less Human Motion Capture

Pons-Moll, G., Rosenhahn, B.

In IEEE Workshop on Applications of Computer Vision (WACV),, December 2009 (inproceedings)

pdf [BibTex]

2009

pdf [BibTex]


no image
Background Subtraction Based on Rank Constraint for Point Trajectories

Ahmad, A., Del Bue, A., Lima, P.

In pages: 1-3, October 2009 (inproceedings)

Abstract
This work deals with a background subtraction algorithm for a fish-eye lens camera having 3 degrees of freedom, 2 in translation and 1 in rotation. The core assumption in this algorithm is that the background is considered to be composed of a dominant static plane in the world frame. The novelty lies in developing a rank-constraint based background subtraction for equidistant projection model, a property of the fish-eye lens. A detail simulation result is presented to support the hypotheses explained in this paper.

link (url) [BibTex]

link (url) [BibTex]


Parametric Modeling of the Beating Heart with Respiratory Motion Extracted from Magnetic Resonance Images
Parametric Modeling of the Beating Heart with Respiratory Motion Extracted from Magnetic Resonance Images

Pons-Moll, G., Crosas, C., Tadmor, G., MacLeod, R., Rosenhahn, B., Brooks, D.

In IEEE Computers in Cardiology (CINC), September 2009 (inproceedings)

[BibTex]

[BibTex]


Computer cursor control by motor cortical signals in humans with tetraplegia
Computer cursor control by motor cortical signals in humans with tetraplegia

Kim, S., Simeral, J. D., Hochberg, L. R., Donoghue, J. P., Black, M. J.

In 7th Asian Control Conference, ASCC09, pages: 988-993, Hong Kong, China, August 2009 (inproceedings)

pdf [BibTex]

pdf [BibTex]


Fields of Experts
Fields of Experts

Roth, S., Black, M. J.

International Journal of Computer Vision (IJCV), 82(2):205-29, April 2009 (article)

Abstract
We develop a framework for learning generic, expressive image priors that capture the statistics of natural scenes and can be used for a variety of machine vision tasks. The approach provides a practical method for learning high-order Markov random field (MRF) models with potential functions that extend over large pixel neighborhoods. These clique potentials are modeled using the Product-of-Experts framework that uses non-linear functions of many linear filter responses. In contrast to previous MRF approaches all parameters, including the linear filters themselves, are learned from training data. We demonstrate the capabilities of this Field-of-Experts model with two example applications, image denoising and image inpainting, which are implemented using a simple, approximate inference scheme. While the model is trained on a generic image database and is not tuned toward a specific application, we obtain results that compete with specialized techniques.

pdf pdf from publisher [BibTex]

pdf pdf from publisher [BibTex]


no image
Classification of colon polyps in NBI endoscopy using vascularization features

Stehle, T., Auer, R., Gross, S., Behrens, A., Wulff, J., Aach, T., Winograd, R., Trautwein, C., Tischendorf, J.

In Medical Imaging 2009: Computer-Aided Diagnosis, 7260, (Editors: N. Karssemeijer and M. L. Giger), SPIE, February 2009 (inproceedings)

Abstract
The evolution of colon cancer starts with colon polyps. There are two different types of colon polyps, namely hyperplasias and adenomas. Hyperplasias are benign polyps which are known not to evolve into cancer and, therefore, do not need to be removed. By contrast, adenomas have a strong tendency to become malignant. Therefore, they have to be removed immediately via polypectomy. For this reason, a method to differentiate reliably adenomas from hyperplasias during a preventive medical endoscopy of the colon (colonoscopy) is highly desirable. A recent study has shown that it is possible to distinguish both types of polyps visually by means of their vascularization. Adenomas exhibit a large amount of blood vessel capillaries on their surface whereas hyperplasias show only few of them. In this paper, we show the feasibility of computer-based classification of colon polyps using vascularization features. The proposed classification algorithm consists of several steps: For the critical part of vessel segmentation, we implemented and compared two segmentation algorithms. After a skeletonization of the detected blood vessel candidates, we used the results as seed points for the Fast Marching algorithm which is used to segment the whole vessel lumen. Subsequently, features are computed from this segmentation which are then used to classify the polyps. In leave-one-out tests on our polyp database (56 polyps), we achieve a correct classification rate of approximately 90%.

DOI [BibTex]

DOI [BibTex]


{One-shot scanning using de bruijn spaced grids}
One-shot scanning using de bruijn spaced grids

Ulusoy, A., Calakli, F., Taubin, G.

In Computer Vision Workshops (ICCV Workshops), 2009 IEEE 12th International Conference on, pages: 1786-1792, IEEE, 2009 (inproceedings)

Abstract
In this paper we present a new one-shot method to reconstruct the shape of dynamic 3D objects and scenes based on active illumination. In common with other related prior-art methods, a static grid pattern is projected onto the scene, a video sequence of the illuminated scene is captured, a shape estimate is produced independently for each video frame, and the one-shot property is realized at the expense of space resolution. The main challenge in grid-based one-shot methods is to engineer the pattern and algorithms so that the correspondence between pattern grid points and their images can be established very fast and without uncertainty. We present an efficient one-shot method which exploits simple geometric constraints to solve the correspondence problem. We also introduce De Bruijn spaced grids, a novel grid pattern, and show with strong empirical data that the resulting scheme is much more robust compared to those based on uniform spaced grids.

pdf link (url) DOI [BibTex]

pdf link (url) DOI [BibTex]


On feature combination for multiclass object classification
On feature combination for multiclass object classification

Gehler, P., Nowozin, S.

In Proceedings of the Twelfth IEEE International Conference on Computer Vision, pages: 221-228, 2009, oral presentation (inproceedings)

project page, code, data GoogleScholar pdf DOI [BibTex]

project page, code, data GoogleScholar pdf DOI [BibTex]


Estimating human shape and pose from a single image
Estimating human shape and pose from a single image

Guan, P., Weiss, A., Balan, A., Black, M. J.

In Int. Conf. on Computer Vision, ICCV, pages: 1381-1388, 2009 (inproceedings)

Abstract
We describe a solution to the challenging problem of estimating human body shape from a single photograph or painting. Our approach computes shape and pose parameters of a 3D human body model directly from monocular image cues and advances the state of the art in several directions. First, given a user-supplied estimate of the subject's height and a few clicked points on the body we estimate an initial 3D articulated body pose and shape. Second, using this initial guess we generate a tri-map of regions inside, outside and on the boundary of the human, which is used to segment the image using graph cuts. Third, we learn a low-dimensional linear model of human shape in which variations due to height are concentrated along a single dimension, enabling height-constrained estimation of body shape. Fourth, we formulate the problem of parametric human shape from shading. We estimate the body pose, shape and reflectance as well as the scene lighting that produces a synthesized body that robustly matches the image evidence. Quantitative experiments demonstrate how smooth shading provides powerful constraints on human shape. We further demonstrate a novel application in which we extract 3D human models from archival photographs and paintings.

pdf video - mov 25MB video - mp4 10MB YouTube Project Page [BibTex]

pdf video - mov 25MB video - mp4 10MB YouTube Project Page [BibTex]


Segmentation, Ordering and Multi-object Tracking Using Graphical   Models
Segmentation, Ordering and Multi-object Tracking Using Graphical Models

Wang, C., Gorce, M. D. L., Paragios, N.

In IEEE International Conference on Computer Vision (ICCV), 2009 (inproceedings)

pdf [BibTex]

pdf [BibTex]


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Evaluating the potential of primary motor and premotor cortex for mutltidimensional neuroprosthetic control of complete reaching and grasping actions

Vargas-Irwin, C. E., Yadollahpour, P., Shakhnarovich, G., Black, M. J., Donoghue, J. P.

2009 Abstract Viewer and Itinerary Planner. Society for Neuroscience, Society for Neuroscience, 2009, Online (conference)

[BibTex]

[BibTex]


Modeling and Evaluation of Human-to-Robot Mapping of Grasps
Modeling and Evaluation of Human-to-Robot Mapping of Grasps

Romero, J., Kjellström, H., Kragic, D.

In International Conference on Advanced Robotics (ICAR), pages: 1-6, 2009 (inproceedings)

Pdf [BibTex]

Pdf [BibTex]


An additive latent feature model for transparent object recognition
An additive latent feature model for transparent object recognition

Fritz, M., Black, M., Bradski, G., Karayev, S., Darrell, T.

In Advances in Neural Information Processing Systems 22, NIPS, pages: 558-566, MIT Press, 2009 (inproceedings)

pdf slides [BibTex]

pdf slides [BibTex]


Let the kernel figure it out; Principled learning of pre-processing for kernel classifiers
Let the kernel figure it out; Principled learning of pre-processing for kernel classifiers

Gehler, P., Nowozin, S.

In Proceedings of the Conference on Computer Vision and Pattern Recognition (CVPR), pages: 2836-2843, IEEE Computer Society, 2009 (inproceedings)

doi project page pdf [BibTex]

doi project page pdf [BibTex]


Monocular Real-Time 3D Articulated Hand Pose Estimation
Monocular Real-Time 3D Articulated Hand Pose Estimation

Romero, J., Kjellström, H., Kragic, D.

In IEEE-RAS International Conference on Humanoid Robots, pages: 87-92, 2009 (inproceedings)

Pdf [BibTex]

Pdf [BibTex]


Grasp Recognition and Mapping on Humanoid Robots
Grasp Recognition and Mapping on Humanoid Robots

Do, M., Romero, J., Kjellström, H., Azad, P., Asfour, T., Kragic, D., Dillmann, R.

In IEEE-RAS International Conference on Humanoid Robots, pages: 465-471, 2009 (inproceedings)

Pdf Video [BibTex]

Pdf Video [BibTex]


4D Cardiac Segmentation of the Epicardium and Left Ventricle
4D Cardiac Segmentation of the Epicardium and Left Ventricle

Pons-Moll, G., Tadmor, G., MacLeod, R. S., Rosenhahn, B., Brooks, D. H.

In World Congress of Medical Physics and Biomedical Engineering (WC), 2009 (inproceedings)

[BibTex]

[BibTex]


Geometric Potential Force for the Deformable Model
Geometric Potential Force for the Deformable Model

Si Yong Yeo, Xianghua Xie, Igor Sazonov, Perumal Nithiarasu

In The 20th British Machine Vision Conference, pages: 1-11, 2009 (inproceedings)

Abstract
We propose a new external force field for deformable models which can be conve- niently generalized to high dimensions. The external force field is based on hypothesized interactions between the relative geometries of the deformable model and image gradi- ents. The evolution of the deformable model is solved using the level set method. The dynamic interaction forces between the geometries can greatly improve the deformable model performance in acquiring complex geometries and highly concave boundaries, and in dealing with weak image edges. The new deformable model can handle arbi- trary cross-boundary initializations. Here, we show that the proposed method achieve significant improvements when compared against existing state-of-the-art techniques.

[BibTex]

[BibTex]


Left Ventricular Regional Wall Curvedness and Wall Stress in Patients with Ischemic Dilated Cardiomyopathy
Left Ventricular Regional Wall Curvedness and Wall Stress in Patients with Ischemic Dilated Cardiomyopathy

Liang Zhong, Yi Su, Si Yong Yeo, Ru San Tan Dhanjoo Ghista, Ghassan Kassab

American Journal of Physiology – Heart and Circulatory Physiology, 296(3):H573-84, 2009 (article)

Abstract
Geometric remodeling of the left ventricle (LV) after myocardial infarction is associated with changes in myocardial wall stress. The objective of this study was to determine the regional curvatures and wall stress based on three-dimensional (3-D) reconstructions of the LV using MRI. Ten patients with ischemic dilated cardiomyopathy (IDCM) and 10 normal subjects underwent MRI scan. The IDCM patients also underwent delayed gadolinium-enhancement imaging to delineate the extent of myocardial infarct. Regional curvedness, local radii of curvature, and wall thickness were calculated. The percent curvedness change between end diastole and end systole was also calculated. In normal heart, a short- and long-axis two-dimensional analysis showed a 41 +/- 11% and 45 +/- 12% increase of the mean of peak systolic wall stress between basal and apical sections, respectively. However, 3-D analysis showed no significant difference in peak systolic wall stress from basal and apical sections (P = 0.298, ANOVA). LV shape differed between IDCM patients and normal subjects in several ways: LV shape was more spherical (sphericity index = 0.62 +/- 0.08 vs. 0.52 +/- 0.06, P < 0.05), curvedness at end diastole (mean for 16 segments = 0.034 +/- 0.0056 vs. 0.040 +/- 0.0071 mm(-1), P < 0.001) and end systole (mean for 16 segments = 0.037 +/- 0.0068 vs. 0.067 +/- 0.020 mm(-1), P < 0.001) was affected by infarction, and peak systolic wall stress was significantly increased at each segment in IDCM patients. The 3-D quantification of regional wall stress by cardiac MRI provides more precise evaluation of cardiac mechanics. Identification of regional curvedness and wall stresses helps delineate the mechanisms of LV remodeling in IDCM and may help guide therapeutic LV restoration.

[BibTex]

[BibTex]


Level Set Based Automatic Segmentation of Human Aorta
Level Set Based Automatic Segmentation of Human Aorta

Si Yong Yeo, Xianghua Xie, Igor Sazonov, Perumal Nithiarasu

In International Conference on Computational & Mathematical Biomedical Engineering, pages: 242-245, 2009 (inproceedings)

[BibTex]

[BibTex]


A Curvature-Based Approach for Left Ventricular Shape Analysis from Cardiac Magnetic Resonance Imaging
A Curvature-Based Approach for Left Ventricular Shape Analysis from Cardiac Magnetic Resonance Imaging

Si Yong Yeo, Liang Zhong, Yi Su, Ru San Tan, Dhanjoo Ghista

Medical & Biological Engineering & Computing, 47(3):313-322, 2009 (article)

Abstract
It is believed that left ventricular (LV) regional shape is indicative of LV regional function, and cardiac pathologies are often associated with regional alterations in ventricular shape. In this article, we present a set of procedures for evaluating regional LV surface shape from anatomically accurate models reconstructed from cardiac magnetic resonance (MR) images. LV surface curvatures are computed using local surface fitting method, which enables us to assess regional LV shape and its variation. Comparisons are made between normal and diseased hearts. It is illustrated that LV surface curvatures at different regions of the normal heart are higher than those of the diseased heart. Also, the normal heart experiences a larger change in regional curvedness during contraction than the diseased heart. It is believed that with a wide range of dataset being evaluated, this approach will provide a new and efficient way of quantifying LV regional function.

link (url) [BibTex]

link (url) [BibTex]


In Defense of Orthonormality Constraints for Nonrigid Structure from Motion
In Defense of Orthonormality Constraints for Nonrigid Structure from Motion

Akhter, I., Sheikh, Y., Khan, S.

In Computer Vision and Pattern Recognition, 2009. CVPR 2009. IEEE Conference on, pages: 2447-2453, 2009 (inproceedings)

Abstract
In factorization approaches to nonrigid structure from motion, the 3D shape of a deforming object is usually modeled as a linear combination of a small number of basis shapes. The original approach to simultaneously estimate the shape basis and nonrigid structure exploited orthonormality constraints for metric rectification. Recently, it has been asserted that structure recovery through orthonormality constraints alone is inherently ambiguous and cannot result in a unique solution. This assertion has been accepted as conventional wisdom and is the justification of many remedial heuristics in literature. Our key contribution is to prove that orthonormality constraints are in fact sufficient to recover the 3D structure from image observations alone. We characterize the true nature of the ambiguity in using orthonormality constraints for the shape basis and show that it has no impact on structure reconstruction. We conclude from our experimentation that the primary challenge in using shape basis for nonrigid structure from motion is the difficulty in the optimization problem rather than the ambiguity in orthonormality constraints.

pdf [BibTex]

pdf [BibTex]


no image
Dynamic distortion correction for endoscopy systems with exchangeable optics

Stehle, T., Hennes, M., Gross, S., Behrens, A., Wulff, J., Aach, T.

In Bildverarbeitung für die Medizin 2009, pages: 142-146, Springer Berlin Heidelberg, 2009 (inproceedings)

Abstract
Endoscopic images are strongly affected by lens distortion caused by the use of wide angle lenses. In case of endoscopy systems with exchangeable optics, e.g. in bladder endoscopy or sinus endoscopy, the camera sensor and the optics do not form a rigid system but they can be shifted and rotated with respect to each other during an examination. This flexibility has a major impact on the location of the distortion centre as it is moved along with the optics. In this paper, we describe an algorithm for the dynamic correction of lens distortion in cystoscopy which is based on a one time calibration. For the compensation, we combine a conventional static method for distortion correction with an algorithm to detect the position and the orientation of the elliptic field of view. This enables us to estimate the position of the distortion centre according to the relative movement of camera and optics. Therewith, a distortion correction for arbitrary rotation angles and shifts becomes possible without performing static calibrations for every possible combination of shifts and angles beforehand.

link (url) DOI [BibTex]

link (url) DOI [BibTex]


no image
Computational mechanisms for the recognition of time sequences of images in the visual cortex

Tan, C., Jhuang, H., Singer, J., Serre, T., Sheinberg, D., Poggio, T.

Society for Neuroscience, 2009 (conference)

pdf [BibTex]

pdf [BibTex]


Interactive Inverse Kinematics for Monocular Motion Estimation
Interactive Inverse Kinematics for Monocular Motion Estimation

Morten Engell-Norregaard, Soren Hauberg, Jerome Lapuyade, Kenny Erleben, Kim S. Pedersen

In The 6th Workshop on Virtual Reality Interaction and Physical Simulation (VRIPHYS), 2009 (inproceedings)

Conference site Paper site [BibTex]

Conference site Paper site [BibTex]


A Comprehensive Grasp Taxonomy
A Comprehensive Grasp Taxonomy

Feix, T., Pawlik, R., Schmiedmayer, H., Romero, J., Kragic, D.

In Robotics, Science and Systems: Workshop on Understanding the Human Hand for Advancing Robotic Manipulation, 2009 (inproceedings)

Pdf [BibTex]

Pdf [BibTex]


no image
Population coding of ground truth motion in natural scenes in the early visual system

Stanley, G., Black, M. J., Lewis, J., Desbordes, G., Jin, J., Alonso, J.

COSYNE, 2009 (conference)

[BibTex]

[BibTex]


Segmentation of Human Upper Airway Using a Level Set Based Deformable Model
Segmentation of Human Upper Airway Using a Level Set Based Deformable Model

Si Yong Yeo, Xianghua Xie, Igor Sazonov, Perumal Nithiarasu

In The 13th Medical Image Understanding and Analysis, 2009 (inproceedings)

[BibTex]

[BibTex]


Three Dimensional Monocular Human Motion Analysis in End-Effector Space
Three Dimensional Monocular Human Motion Analysis in End-Effector Space

Soren Hauberg, Jerome Lapuyade, Morten Engell-Norregaard, Kenny Erleben, Kim S. Pedersen

In Energy Minimization Methods in Computer Vision and Pattern Recognition, 5681, pages: 235-248, Lecture Notes in Computer Science, (Editors: Cremers, Daniel and Boykov, Yuri and Blake, Andrew and Schmidt, Frank), Springer Berlin Heidelberg, 2009 (inproceedings)

Publishers site Paper site PDF [BibTex]

Publishers site Paper site PDF [BibTex]


no image
Decoding visual motion from correlated firing of thalamic neurons

Stanley, G. B., Black, M. J., Desbordes, G., Jin, J., Wang, Y., Alonso, J.

2009 Abstract Viewer and Itinerary Planner. Society for Neuroscience, Society for Neuroscience, 2009 (conference)

[BibTex]

[BibTex]

2000


Probabilistic detection and tracking of motion boundaries
Probabilistic detection and tracking of motion boundaries

Black, M. J., Fleet, D. J.

Int. J. of Computer Vision, 38(3):231-245, July 2000 (article)

Abstract
We propose a Bayesian framework for representing and recognizing local image motion in terms of two basic models: translational motion and motion boundaries. Motion boundaries are represented using a non-linear generative model that explicitly encodes the orientation of the boundary, the velocities on either side, the motion of the occluding edge over time, and the appearance/disappearance of pixels at the boundary. We represent the posterior probability distribution over the model parameters given the image data using discrete samples. This distribution is propagated over time using a particle filtering algorithm. To efficiently represent such a high-dimensional space we initialize samples using the responses of a low-level motion discontinuity detector. The formulation and computational model provide a general probabilistic framework for motion estimation with multiple, non-linear, models.

pdf pdf from publisher Video [BibTex]

2000

pdf pdf from publisher Video [BibTex]


Stochastic tracking of {3D} human figures using {2D} image motion
Stochastic tracking of 3D human figures using 2D image motion

(Winner of the 2010 Koenderink Prize for Fundamental Contributions in Computer Vision)

Sidenbladh, H., Black, M. J., Fleet, D.

In European Conference on Computer Vision, ECCV, pages: 702-718, LNCS 1843, Springer Verlag, Dublin, Ireland, June 2000 (inproceedings)

Abstract
A probabilistic method for tracking 3D articulated human figures in monocular image sequences is presented. Within a Bayesian framework, we define a generative model of image appearance, a robust likelihood function based on image gray level differences, and a prior probability distribution over pose and joint angles that models how humans move. The posterior probability distribution over model parameters is represented using a discrete set of samples and is propagated over time using particle filtering. The approach extends previous work on parameterized optical flow estimation to exploit a complex 3D articulated motion model. It also extends previous work on human motion tracking by including a perspective camera model, by modeling limb self occlusion, and by recovering 3D motion from a monocular sequence. The explicit posterior probability distribution represents ambiguities due to image matching, model singularities, and perspective projection. The method relies only on a frame-to-frame assumption of brightness constancy and hence is able to track people under changing viewpoints, in grayscale image sequences, and with complex unknown backgrounds.

pdf code [BibTex]

pdf code [BibTex]


no image
Functional analysis of human motion data

Ormoneit, D., Hastie, T., Black, M. J.

In In Proc. 5th World Congress of the Bernoulli Society for Probability and Mathematical Statistics and 63rd Annual Meeting of the Institute of Mathematical Statistics, Guanajuato, Mexico, May 2000 (inproceedings)

[BibTex]

[BibTex]


no image
Stochastic modeling and tracking of human motion

Ormoneit, D., Sidenbladh, H., Black, M. J., Hastie, T.

Learning 2000, Snowbird, UT, April 2000 (conference)

abstract [BibTex]

abstract [BibTex]


A framework for modeling the appearance of {3D} articulated figures
A framework for modeling the appearance of 3D articulated figures

Sidenbladh, H., De la Torre, F., Black, M. J.

In Int. Conf. on Automatic Face and Gesture Recognition, pages: 368-375, Grenoble, France, March 2000 (inproceedings)

pdf [BibTex]

pdf [BibTex]


Design and use of linear models for image motion analysis
Design and use of linear models for image motion analysis

Fleet, D. J., Black, M. J., Yacoob, Y., Jepson, A. D.

Int. J. of Computer Vision, 36(3):171-193, 2000 (article)

Abstract
Linear parameterized models of optical flow, particularly affine models, have become widespread in image motion analysis. The linear model coefficients are straightforward to estimate, and they provide reliable estimates of the optical flow of smooth surfaces. Here we explore the use of parameterized motion models that represent much more varied and complex motions. Our goals are threefold: to construct linear bases for complex motion phenomena; to estimate the coefficients of these linear models; and to recognize or classify image motions from the estimated coefficients. We consider two broad classes of motions: i) generic “motion features” such as motion discontinuities and moving bars; and ii) non-rigid, object-specific, motions such as the motion of human mouths. For motion features we construct a basis of steerable flow fields that approximate the motion features. For object-specific motions we construct basis flow fields from example motions using principal component analysis. In both cases, the model coefficients can be estimated directly from spatiotemporal image derivatives with a robust, multi-resolution scheme. Finally, we show how these model coefficients can be use to detect and recognize specific motions such as occlusion boundaries and facial expressions.

pdf [BibTex]

pdf [BibTex]


Robustly estimating changes in image appearance
Robustly estimating changes in image appearance

Black, M. J., Fleet, D. J., Yacoob, Y.

Computer Vision and Image Understanding, 78(1):8-31, 2000 (article)

Abstract
We propose a generalized model of image “appearance change” in which brightness variation over time is represented as a probabilistic mixture of different causes. We define four generative models of appearance change due to (1) object or camera motion; (2) illumination phenomena; (3) specular reflections; and (4) “iconic changes” which are specific to the objects being viewed. These iconic changes include complex occlusion events and changes in the material properties of the objects. We develop a robust statistical framework for recovering these appearance changes in image sequences. This approach generalizes previous work on optical flow to provide a richer description of image events and more reliable estimates of image motion in the presence of shadows and specular reflections.

pdf pdf from publisher DOI [BibTex]

pdf pdf from publisher DOI [BibTex]

1996


Cardboard people: A parameterized model of articulated motion
Cardboard people: A parameterized model of articulated motion

Ju, S. X., Black, M. J., Yacoob, Y.

In 2nd Int. Conf. on Automatic Face- and Gesture-Recognition, pages: 38-44, Killington, Vermont, October 1996 (inproceedings)

Abstract
We extend the work of Black and Yacoob on the tracking and recognition of human facial expressions using parameterized models of optical flow to deal with the articulated motion of human limbs. We define a "cardboard person model" in which a person's limbs are represented by a set of connected planar patches. The parameterized image motion of these patches is constrained to enforce articulated motion and is solved for directly using a robust estimation technique. The recovered motion parameters provide a rich and concise description of the activity that can be used for recognition. We propose a method for performing view-based recognition of human activities from the optical flow parameters that extends previous methods to cope with the cyclical nature of human motion. We illustrate the method with examples of tracking human legs over long image sequences.

pdf [BibTex]

1996

pdf [BibTex]


Estimating optical flow in segmented images using variable-order parametric models with local deformations
Estimating optical flow in segmented images using variable-order parametric models with local deformations

Black, M. J., Jepson, A.

IEEE Transactions on Pattern Analysis and Machine Intelligence, 18(10):972-986, October 1996 (article)

Abstract
This paper presents a new model for estimating optical flow based on the motion of planar regions plus local deformations. The approach exploits brightness information to organize and constrain the interpretation of the motion by using segmented regions of piecewise smooth brightness to hypothesize planar regions in the scene. Parametric flow models are estimated in these regions in a two step process which first computes a coarse fit and estimates the appropriate parameterization of the motion of the region (two, six, or eight parameters). The initial fit is refined using a generalization of the standard area-based regression approaches. Since the assumption of planarity is likely to be violated, we allow local deformations from the planar assumption in the same spirit as physically-based approaches which model shape using coarse parametric models plus local deformations. This parametric+deformation model exploits the strong constraints of parametric approaches while retaining the adaptive nature of regularization approaches. Experimental results on a variety of images indicate that the parametric+deformation model produces accurate flow estimates while the incorporation of brightness segmentation provides precise localization of motion boundaries.

pdf pdf from publisher [BibTex]

pdf pdf from publisher [BibTex]


On the unification of line processes, outlier rejection, and robust statistics with applications in early vision
On the unification of line processes, outlier rejection, and robust statistics with applications in early vision

Black, M., Rangarajan, A.

International Journal of Computer Vision , 19(1):57-92, July 1996 (article)

Abstract
The modeling of spatial discontinuities for problems such as surface recovery, segmentation, image reconstruction, and optical flow has been intensely studied in computer vision. While “line-process” models of discontinuities have received a great deal of attention, there has been recent interest in the use of robust statistical techniques to account for discontinuities. This paper unifies the two approaches. To achieve this we generalize the notion of a “line process” to that of an analog “outlier process” and show how a problem formulated in terms of outlier processes can be viewed in terms of robust statistics. We also characterize a class of robust statistical problems for which an equivalent outlier-process formulation exists and give a straightforward method for converting a robust estimation problem into an outlier-process formulation. We show how prior assumptions about the spatial structure of outliers can be expressed as constraints on the recovered analog outlier processes and how traditional continuation methods can be extended to the explicit outlier-process formulation. These results indicate that the outlier-process approach provides a general framework which subsumes the traditional line-process approaches as well as a wide class of robust estimation problems. Examples in surface reconstruction, image segmentation, and optical flow are presented to illustrate the use of outlier processes and to show how the relationship between outlier processes and robust statistics can be exploited. An appendix provides a catalog of common robust error norms and their equivalent outlier-process formulations.

pdf pdf from publisher DOI [BibTex]


Skin and Bones: Multi-layer, locally affine, optical flow and regularization with transparency
Skin and Bones: Multi-layer, locally affine, optical flow and regularization with transparency

(Nominated: Best paper)

Ju, S., Black, M. J., Jepson, A. D.

In IEEE Conf. on Computer Vision and Pattern Recognition, CVPR’96, pages: 307-314, San Francisco, CA, June 1996 (inproceedings)

pdf [BibTex]

pdf [BibTex]


EigenTracking: Robust matching and tracking of articulated objects using a view-based representation
EigenTracking: Robust matching and tracking of articulated objects using a view-based representation

Black, M. J., Jepson, A.

In Proc. Fourth European Conf. on Computer Vision, ECCV’96, pages: 329-342, LNCS 1064, Springer Verlag, Cambridge, England, April 1996 (inproceedings)

pdf video [BibTex]

pdf video [BibTex]


The robust estimation of multiple motions: Parametric and piecewise-smooth flow fields
The robust estimation of multiple motions: Parametric and piecewise-smooth flow fields

Black, M. J., Anandan, P.

Computer Vision and Image Understanding, 63(1):75-104, January 1996 (article)

Abstract
Most approaches for estimating optical flow assume that, within a finite image region, only a single motion is present. This single motion assumption is violated in common situations involving transparency, depth discontinuities, independently moving objects, shadows, and specular reflections. To robustly estimate optical flow, the single motion assumption must be relaxed. This paper presents a framework based on robust estimation that addresses violations of the brightness constancy and spatial smoothness assumptions caused by multiple motions. We show how the robust estimation framework can be applied to standard formulations of the optical flow problem thus reducing their sensitivity to violations of their underlying assumptions. The approach has been applied to three standard techniques for recovering optical flow: area-based regression, correlation, and regularization with motion discontinuities. This paper focuses on the recovery of multiple parametric motion models within a region, as well as the recovery of piecewise-smooth flow fields, and provides examples with natural and synthetic image sequences.

pdf pdf from publisher [BibTex]

pdf pdf from publisher [BibTex]

1992


Psychophysical implications of temporal persistence in early vision: A computational account of representational momentum
Psychophysical implications of temporal persistence in early vision: A computational account of representational momentum

Tarr, M. J., Black, M. J.

Investigative Ophthalmology and Visual Science Supplement, Vol. 36, No. 4, 33, pages: 1050, May 1992 (conference)

abstract [BibTex]

1992

abstract [BibTex]


Combining intensity and motion for incremental segmentation and tracking over long image sequences
Combining intensity and motion for incremental segmentation and tracking over long image sequences

Black, M. J.

In Proc. Second European Conf. on Computer Vision, ECCV-92, pages: 485-493, LNCS 588, Springer Verlag, May 1992 (inproceedings)

pdf video abstract [BibTex]

pdf video abstract [BibTex]