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80
Automatic camera recovery for closed or open image sequences
 In Proceedings of the European Conference on Computer Vision
, 1998
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The active recovery of 3D motion trajectories and their use in prediction
 IEEE Transactions on Pattern Analysis and Machine Intelligence
, 1997
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Active camera calibration for a headeye platform using the variable statedimension filter
 IEEE Trans. Pattern Anal. Mach. Intell
, 1996
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Using Geometric Constraints through Parallelepipeds for Calibration and 3D Modelling
, 2005
"... This paper concerns the incorporation of geometric information in camera calibration and 3D modeling. Using geometric constraints enables more stable results and allows us to perform tasks with fewer images. Our approach is motivated and developed within a framework of semiautomatic 3D modeling, wh ..."
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Cited by 36 (4 self)
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This paper concerns the incorporation of geometric information in camera calibration and 3D modeling. Using geometric constraints enables more stable results and allows us to perform tasks with fewer images. Our approach is motivated and developed within a framework of semiautomatic 3D modeling, where the user defines geometric primitives and constraints between them. It is based on the observation that constraints, such as coplanarity, parallelism, or orthogonality, are often embedded intuitively in parallelepipeds. Moreover, parallelepipeds are easy to delineate by a user and are well adapted to model the main structure of, e.g., architectural scenes. In this paper, first a duality that exists between the shape parameters of a parallelepiped and the intrinsic parameters of a camera is described. Then, a factorizationbased algorithm exploiting this relation is developed. Using images of parallelepipeds, it allows us to simultaneously calibrate cameras, recover shapes of parallelepipeds, and estimate the relative pose of all entities. Besides geometric constraints expressed via parallelepipeds, our approach simultaneously takes into account the usual selfcalibration constraints on cameras. The proposed algorithm is completed by a study of the singular cases of the calibration method. A complete method for the reconstruction of scene primitives that are not modeled by parallelepipeds is also briefly described. The proposed methods are validated by various experiments with real and simulated data, for singleview as well as multiview cases.
Visual Motion Analysis by Probabilistic Propagation of Conditional Density
, 1998
"... This thesis establishes a stochastic framework for tracking curves in visual clutter, using a Bayesian randomsampling algorithm. The approach is rooted in ideas from statistics, control theory and computer vision. The problem is to track outlines and features of foreground objects, modelled as curv ..."
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Cited by 36 (0 self)
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This thesis establishes a stochastic framework for tracking curves in visual clutter, using a Bayesian randomsampling algorithm. The approach is rooted in ideas from statistics, control theory and computer vision. The problem is to track outlines and features of foreground objects, modelled as curves, as they move in substantial clutter, and to do it at, or close to, video framerate. The algorithm, named Condensation, for Conditional density propagation, has recently been derived independently by several researchers, and is generating signi cant interest in the statistics and signal processing communities. This thesis contributes to the literature on Condensationlike lters by presenting some novel applications of and extensions to the basic algorithm, and contributes to the visual motion estimation literature by demonstrating high tracking performance in cluttered environments. Despite its power the Condensation algorithm has a remarkably simple form and this allows the use of nonlinear motion models which combine characteristics of discrete Hidden Markov Models with the continuous AutoRegressive Process motion models traditionally used in Kalman lters. These mixed discretecontinuous models have promising applications to the emerging eld of perception of action. This thesis also implements two algorithms to smooth the output of the Condensation lter which improves the accuracy of motion estimation in a batchmode procedure after tracking is complete.
I.D.: Articulated structure from motion by factorization
 In: Proc. CVPR, IEEE Computer Society
, 2005
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Synchronizing image sequences of nonrigid objects
 In Proc. 14th British Machine Vision Conf
, 2003
"... For stereopsis, images of a given scene must be captured at the same instant to ensure temporal consistency. For sequences of images (i.e. video streams) this requires the potentially costly and technically complex process of synchronizing cameras. We present a simple but effective method for automa ..."
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Cited by 30 (5 self)
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For stereopsis, images of a given scene must be captured at the same instant to ensure temporal consistency. For sequences of images (i.e. video streams) this requires the potentially costly and technically complex process of synchronizing cameras. We present a simple but effective method for automatically recovering the subframe temporal offset between image sequences taken using unsynchronized cameras. Having recovered the offset, we obtain the affine structure of a nonrigid motion. The technique is demonstrated for the application of human motion capture. 1
A Six Point Solution for Structure and Motion
, 2000
"... The paper has two main contributions: The first is a set of methods for computing structure and motion for m >= 3 views of 6 points. It is shown that a geometric image error can be minimized over all views by a simple three parameter numerical optimization. Then, that an algebraic image error ..."
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Cited by 21 (2 self)
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The paper has two main contributions: The first is a set of methods for computing structure and motion for m >= 3 views of 6 points. It is shown that a geometric image error can be minimized over all views by a simple three parameter numerical optimization. Then, that an algebraic image error can be minimized over all views by computing the solution to a cubic in one variable. Finally, a minor point, is that this "quasilinear" linear solution enables a more concise algorithm, than any given previously, for the reconstruction of 6 points in 3 views. The second
3D Trajectories from a Single Viewpoint using Shadows
 Proc. BMVC
, 1998
"... We consider the problem of obtaining the 3D trajectory of a ball from a sequence of images taken with a camera which is possibly rotating and zooming (but not translating). Techniques are developed to compute the component of image motion of the ball due to camera rotation and zoom, using optic f ..."
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Cited by 16 (2 self)
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We consider the problem of obtaining the 3D trajectory of a ball from a sequence of images taken with a camera which is possibly rotating and zooming (but not translating). Techniques are developed to compute the component of image motion of the ball due to camera rotation and zoom, using optic flow. The 3D location of the ball in each frame of the sequence is then determined using a novel geometric construction which makes use of shadows on the known ground plane in order to compute the vertical projection of the ball onto the ground, and the height of the ball above the ground. 1 Introduction In the absence of any other constraints, the image projections of world points in a single view of a scene are insufficient to compute a 3D reconstruction of the scene. The most obvious way to obtain 3D structure is therefore to consider multiple views separated spatially (and possibly temporally). An alternative to using multiple viewpoints is to enforce physical and geometric constrai...