%0 Conference Paper
%B Computer Vision and Pattern Recognition, 2007. CVPR '07. IEEE Conference on
%D 2007
%T Efficiently Determining Silhouette Consistency
%A Li Yi
%A Jacobs, David W.
%K camera;scaled
%K consistency;image
%K miscalibrated
%K orthographic
%K problem;silhouette
%K projection;shape-from-silhouette
%K reconstruction;
%X Volume intersection is a frequently used technique to solve the Shape-From-Silhouette problem, which constructs a 3D object estimate from a set of silhouettes taken with calibrated cameras. It is natural to develop an efficient algorithm to determine the consistency of a set of silhouettes before performing time-consuming reconstruction, so that inaccurate silhouettes can be omitted. In this paper we first present a fast algorithm to determine the consistency of three silhouettes from known (but arbitrary) viewing directions, assuming the projection is scaled orthographic. The temporal complexity of the algorithm is linear in the number of points of the silhouette boundaries. We further prove that a set of more than three convex silhouettes are consistent if and only if any three of them are consistent. Another possible application of our approach is to determine the miscalibrated cameras in a large camera system. A consistent subset of cameras can be determined on the fly and miscalibrated cameras can also be recalibrated at a coarse scale. Real and synthesized data are used to demonstrate our results.
%B Computer Vision and Pattern Recognition, 2007. CVPR '07. IEEE Conference on
%P 1 - 8
%8 2007/06//
%G eng
%R 10.1109/CVPR.2007.383161
%0 Conference Paper
%B Computer Vision, 2005. ICCV 2005. Tenth IEEE International Conference on
%D 2005
%T An algebraic approach to surface reconstruction from gradient fields
%A Agrawal,A.
%A Chellapa, Rama
%A Raskar, R.
%K algebra;
%K algebraic
%K approach;
%K Computer
%K confinement;
%K discrete
%K domain
%K error
%K field;
%K from
%K gradient
%K graph
%K image
%K integrability;
%K linear
%K local
%K methods;
%K photometric
%K reconstruction;
%K shading;
%K SHAPE
%K stereo;
%K surface
%K system;
%K theory;
%K vision;
%X Several important problems in computer vision such as shape from shading (SFS) and photometric stereo (PS) require reconstructing a surface from an estimated gradient field, which is usually non-integrable, i.e. have non-zero curl. We propose a purely algebraic approach to enforce integrability in discrete domain. We first show that enforcing integrability can be formulated as solving a single linear system Ax =b over the image. In general, this system is under-determined. We show conditions under which the system can be solved and a method to get to those conditions based on graph theory. The proposed approach is non-iterative, has the important property of local error confinement and can be applied to several problems. Results on SFS and PS demonstrate the applicability of our method.
%B Computer Vision, 2005. ICCV 2005. Tenth IEEE International Conference on
%V 1
%P 174 - 181 Vol. 1 - 174 - 181 Vol. 1
%8 2005/10//
%G eng
%R 10.1109/ICCV.2005.31
%0 Conference Paper
%B Acoustics, Speech, and Signal Processing, 2005. Proceedings. (ICASSP '05). IEEE International Conference on
%D 2005
%T Moving Object Segmentation and Dynamic Scene Reconstruction Using Two Frames
%A Agrawala, Ashok K.
%A Chellapa, Rama
%K 3D
%K analysis;
%K constraints;
%K dynamic
%K ego-motion
%K estimation;
%K flow
%K image
%K images;
%K independent
%K INTENSITY
%K least
%K mean
%K median
%K method;
%K methods;
%K model;
%K MOTION
%K motion;
%K moving
%K object
%K of
%K parallax
%K parallax;
%K parametric
%K processing;
%K reconstruction;
%K scene
%K segmentation;
%K signal
%K squares
%K squares;
%K static
%K structure;
%K subspace
%K surface
%K translational
%K two-frame
%K unconstrained
%K video
%B Acoustics, Speech, and Signal Processing, 2005. Proceedings. (ICASSP '05). IEEE International Conference on
%V 2
%P 705 - 708
%8 2005//18/23
%G eng
%R 10.1109/ICASSP.2005.1415502
%0 Conference Paper
%B Acoustics, Speech, and Signal Processing, 2004. Proceedings. (ICASSP '04). IEEE International Conference on
%D 2004
%T 3D model refinement using surface-parallax
%A Agrawala, Ashok K.
%A Chellapa, Rama
%K 3D
%K adaptive
%K arbitrary
%K camera
%K coarse
%K compensation;
%K Computer
%K DEM;
%K depth
%K digital
%K ELEVATION
%K environments;
%K epipolar
%K estimation;
%K field;
%K image
%K incomplete
%K INTENSITY
%K map;
%K model
%K MOTION
%K parallax;
%K plane-parallax
%K reconstruction;
%K recovery;
%K refinement;
%K sequence;
%K sequences;
%K surface
%K surfaces;
%K urban
%K vision;
%K windowing;
%X We present an approach to update and refine coarse 3D models of urban environments from a sequence of intensity images using surface parallax. This generalizes the plane-parallax recovery methods to surface-parallax using arbitrary surfaces. A coarse and potentially incomplete depth map of the scene obtained from a digital elevation map (DEM) is used as a reference surface which is refined and updated using this approach. The reference depth map is used to estimate the camera motion and the motion of the 3D points on the reference surface is compensated. The resulting parallax, which is an epipolar field, is estimated using an adaptive windowing technique and used to obtain the refined depth map.
%B Acoustics, Speech, and Signal Processing, 2004. Proceedings. (ICASSP '04). IEEE International Conference on
%V 3
%P iii - 285-8 vol.3 - iii - 285-8 vol.3
%8 2004/05//
%G eng
%R 10.1109/ICASSP.2004.1326537
%0 Conference Paper
%B Antennas and Propagation Society International Symposium, 2003. IEEE
%D 2003
%T A 2D profile reconstruction in a multilayered waveguide structure
%A Seydou,F.
%A Duraiswami, Ramani
%A Seppanen,T.
%K (mathematics);
%K 2D
%K dual
%K duality
%K electromagnetic
%K equations;
%K inhomogeneous
%K Maxwell
%K media;
%K method;
%K multilayered
%K multilayers;
%K profile
%K reconstruction;
%K scattering;
%K space
%K structure;
%K theory;
%K wave
%K waveguide
%K waveguides;
%X We discuss the problem of finding a profile or its location for a 2D scattering of electromagnetic waves with fixed frequencies in a waveguide multilayered domain. We use the dual space method (DSM) of Colton and Monk. Our goal is to extend our previous work of TE and TM cases to the more complicated case of a waveguide. We emphasize on the frequency range in the reconstruction.
%B Antennas and Propagation Society International Symposium, 2003. IEEE
%V 1
%P 531 - 534 vol.1 - 531 - 534 vol.1
%8 2003/06//
%G eng
%R 10.1109/APS.2003.1217513
%0 Conference Paper
%B Multimedia and Expo, 2003. ICME '03. Proceedings. 2003 International Conference on
%D 2003
%T View synthesis of articulating humans using visual hull
%A Yue,Zhanfeng
%A Liang Zhao
%A Chellapa, Rama
%K analysis;
%K body
%K convex
%K gesture
%K hull;
%K human
%K image
%K image-based
%K image;
%K mapping;
%K MOTION
%K part
%K parts;
%K postures;
%K recognition;
%K reconstruction;
%K segmentation;
%K silhouette
%K synthesis;
%K TEXTURE
%K texture;
%K view
%K virtual
%K visual
%X In this paper, we present a method, which combines image-based visual hull and human body part segmentation for overcoming the inability of the visual hull method to reconstruct concave regions. The virtual silhouette image corresponding to the given viewing direction is first produced with image-based visual hull. Human body part localization technique is used to segment the input images and the rendered virtual silhouette image into convex body parts. The body parts in the virtual view are generated separately from the corresponding body parts in the input views and then assembled together. The previously rendered silhouette image is used to locate the corresponding body parts in input views and avoid the unconnected or squeezed regions in the assembled final view. Experiments show that this method can improve the reconstruction of concave regions for human postures and texture mapping.
%B Multimedia and Expo, 2003. ICME '03. Proceedings. 2003 International Conference on
%V 1
%P I - 489-92 vol.1 - I - 489-92 vol.1
%8 2003/07//
%G eng
%R 10.1109/ICME.2003.1220961
%0 Conference Paper
%B Multimedia and Expo, 2002. ICME '02. Proceedings. 2002 IEEE International Conference on
%D 2002
%T 3D face reconstruction from video using a generic model
%A Chowdhury, A.R.
%A Chellapa, Rama
%A Krishnamurthy, S.
%A Vo, T.
%K 3D
%K algorithm;
%K algorithms;
%K analysis;
%K Carlo
%K chain
%K Computer
%K Face
%K from
%K function;
%K generic
%K human
%K image
%K Markov
%K MCMC
%K methods;
%K model;
%K Monte
%K MOTION
%K optimisation;
%K OPTIMIZATION
%K processes;
%K processing;
%K recognition;
%K reconstruction
%K reconstruction;
%K sampling;
%K sequence;
%K sequences;
%K SfM
%K signal
%K structure
%K surveillance;
%K video
%K vision;
%X Reconstructing a 3D model of a human face from a video sequence is an important problem in computer vision, with applications to recognition, surveillance, multimedia etc. However, the quality of 3D reconstructions using structure from motion (SfM) algorithms is often not satisfactory. One common method of overcoming this problem is to use a generic model of a face. Existing work using this approach initializes the reconstruction algorithm with this generic model. The problem with this approach is that the algorithm can converge to a solution very close to this initial value, resulting in a reconstruction which resembles the generic model rather than the particular face in the video which needs to be modeled. We propose a method of 3D reconstruction of a human face from video in which the 3D reconstruction algorithm and the generic model are handled separately. A 3D estimate is obtained purely from the video sequence using SfM algorithms without use of the generic model. The final 3D model is obtained after combining the SfM estimate and the generic model using an energy function that corrects for the errors in the estimate by comparing local regions in the two models. The optimization is done using a Markov chain Monte Carlo (MCMC) sampling strategy. The main advantage of our algorithm over others is that it is able to retain the specific features of the face in the video sequence even when these features are different from those of the generic model. The evolution of the 3D model through the various stages of the algorithm is presented.
%B Multimedia and Expo, 2002. ICME '02. Proceedings. 2002 IEEE International Conference on
%V 1
%P 449 - 452 vol.1 - 449 - 452 vol.1
%8 2002///
%G eng
%R 10.1109/ICME.2002.1035815
%0 Conference Paper
%B Image Processing. 2002. Proceedings. 2002 International Conference on
%D 2002
%T Bayesian structure from motion using inertial information
%A Qian,Gang
%A Chellapa, Rama
%A Qinfen Zheng
%K 3D
%K analysis;
%K Bayes
%K Bayesian
%K camera
%K estimation;
%K image
%K images;
%K importance
%K inertial
%K information;
%K methods;
%K MOTION
%K motion;
%K parameter
%K processing;
%K real
%K reconstruction;
%K sampling;
%K scene
%K sensors;
%K sequence;
%K sequences;
%K sequential
%K signal
%K structure-from-motion;
%K synthetic
%K systems;
%K video
%X A novel approach to Bayesian structure from motion (SfM) using inertial information and sequential importance sampling (SIS) is presented. The inertial information is obtained from camera-mounted inertial sensors and is used in the Bayesian SfM approach as prior knowledge of the camera motion in the sampling algorithm. Experimental results using both synthetic and real images show that, when inertial information is used, more accurate results can be obtained or the same estimation accuracy can be obtained at a lower cost.
%B Image Processing. 2002. Proceedings. 2002 International Conference on
%V 3
%P III-425 - III-428 vol.3 - III-425 - III-428 vol.3
%8 2002///
%G eng
%R 10.1109/ICIP.2002.1038996
%0 Conference Paper
%B Document Analysis and Recognition, 1993., Proceedings of the Second International Conference on
%D 1993
%T The processing of form documents
%A David Doermann
%A Rosenfeld, A.
%K AUTOMATIC
%K business
%K detectors;
%K document
%K documents;
%K extraction;
%K feature
%K form
%K forms;
%K generation;
%K generic
%K handling;
%K known
%K markings;
%K model
%K modeling;
%K non-form
%K optimal
%K properties;
%K reconstruction;
%K set;
%K specialized
%K stroke
%K width
%X An overview of an approach to the generic modeling and processing of known forms is presented. The system provides a methodology by which models are generated from regions in the document based on their usage. Automatic extraction of an optimal set of features to be used for registration is proposed, and it is shown how specialized detectors can be designed for each feature based on their position, orientation and width properties. Registration of the form with the model is accomplished using probing to establish correspondence. Form components which are corrupted by markings are detected and isolated, the intersections are interpreted and the properties of the non-form markings are used to reconstruct the strokes through the intersections. The feasibility of these ideas is demonstrated through an implementation of key components of the system
%B Document Analysis and Recognition, 1993., Proceedings of the Second International Conference on
%P 497 - 501
%8 1993/10//
%G eng
%R 10.1109/ICDAR.1993.395687