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100
CoherenceEnhancing Diffusion Filtering
, 1999
"... The completion of interrupted lines or the enhancement of flowlike structures is a challenging task in computer vision, human vision, and image processing. We address this problem by presenting a multiscale method in which a nonlinear diffusion filter is steered by the socalled interest operato ..."
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Cited by 91 (2 self)
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The completion of interrupted lines or the enhancement of flowlike structures is a challenging task in computer vision, human vision, and image processing. We address this problem by presenting a multiscale method in which a nonlinear diffusion filter is steered by the socalled interest operator (secondmoment matrix, structure tensor). An mdimensional formulation of this method is analysed with respect to its wellposedness and scalespace properties. An efficient scheme is presented which uses a stabilization by a semiimplicit additive operator splitting (AOS), and the scalespace behaviour of this method is illustrated by applying it to both 2D and 3D images.
Efficient Impostor Manipulation for RealTime Visualization of Urban Scenery
 EUROGRAPHICS '97 / D. FELLNER AND L. SZIRMAYKALOS (GUEST EDITORS)
, 1997
"... Urban environments present unique challenges to interactive visualization systems, because of the huge complexity of the geometrical data and the widely varying visibility conditions. This paper introduces a new framework for realtime visualisation of such urban scenes. The central concept is tha ..."
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Cited by 71 (4 self)
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Urban environments present unique challenges to interactive visualization systems, because of the huge complexity of the geometrical data and the widely varying visibility conditions. This paper introduces a new framework for realtime visualisation of such urban scenes. The central concept is that of a dynamic segmentation of the dataset, into a local threedimensional model and a set of impostors used to represent distant scenery. A segmentation model is presented, based on inherent urban structure. A new impostor structure is introduced, derived from the levelofdetail approach. Impostors combine threedimensional geometry to correctly model large depth discontinuities and parallax, and textures to rapidly display visual detail. We present the algorithms necessary for the creation of accurate and efficient threedimensional impostors. The implementation of our algorithms allows interactive navigation in complex urban databases, as required by many applications.
A Scheme for CoherenceEnhancing Diffusion Filtering with Optimized Rotation Invariance
, 2000
"... For strongly undirected anisotropic processes such as coherenceenhancing diffusion... ..."
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Cited by 35 (5 self)
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For strongly undirected anisotropic processes such as coherenceenhancing diffusion...
2003) Vision and inertial sensor cooperation using gravity as a vertical reference
 Pattern Analysis and Machine Intelligence, IEEE Transactions on
"... Abstract—This paper explores the combination of inertial sensor data with vision. Visual and inertial sensing are two sensory modalities that can be explored to give robust solutions on image segmentation and recovery of 3D structure from images, increasing the capabilities of autonomous robots and ..."
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Cited by 30 (9 self)
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Abstract—This paper explores the combination of inertial sensor data with vision. Visual and inertial sensing are two sensory modalities that can be explored to give robust solutions on image segmentation and recovery of 3D structure from images, increasing the capabilities of autonomous robots and enlarging the application potential of vision systems. In biological systems, the information provided by the vestibular system is fused at a very early processing stage with vision, playing a key role on the execution of visual movements such as gaze holding and tracking, and the visual cues aid the spatial orientation and body equilibrium. In this paper, we set a framework for using inertial sensor data in vision systems, and describe some results obtained. The unit sphere projection camera model is used, providing a simple model for inertial data integration. Using the vertical reference provided by the inertial sensors, the image horizon line can be determined. Using just one vanishing point and the vertical, we can recover the camera’s focal distance and provide an external bearing for the system’s navigation frame of reference. Knowing the geometry of a stereo rig and its pose from the inertial sensors, the collineation of level planes can be recovered, providing enough restrictions to segment and reconstruct vertical features and leveled planar patches. Index Terms—Image processing and computer vision, edge and feature detection, sensor fusion. æ 1
Clifford Fourier Transform on Vector Fields
 IEEE Transactions on Visualization and Computer Graphics
, 2005
"... Abstract—Image processing and computer vision have robust methods for feature extraction and the computation of derivatives of scalar fields. Furthermore, interpolation and the effects of applying a filter can be analyzed in detail and can be advantages when applying these methods to vector fields t ..."
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Cited by 23 (1 self)
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Abstract—Image processing and computer vision have robust methods for feature extraction and the computation of derivatives of scalar fields. Furthermore, interpolation and the effects of applying a filter can be analyzed in detail and can be advantages when applying these methods to vector fields to obtain a solid theoretical basis for feature extraction. We recently introduced the Clifford convolution, which is an extension of the classical convolution on scalar fields and provides a unified notation for the convolution of scalar and vector fields. It has attractive geometric properties that allow pattern matching on vector fields. In image processing, the convolution and the Fourier transform operators are closely related by the convolution theorem and, in this paper, we extend the Fourier transform to include general elements of Clifford Algebra, called multivectors, including scalars and vectors. The resulting convolution and derivative theorems are extensions of those for convolution and the Fourier transform on scalar fields. The Clifford Fourier transform allows a frequency analysis of vector fields and the behavior of vectorvalued filters. In frequency space, vectors are transformed into general multivectors of the Clifford Algebra. Many basic vectorvalued patterns, such as source, sink, saddle points, and potential vortices, can be described by a few multivectors in frequency space.
Integrating Perceptual and Cognitive Modeling for Adaptive and Intelligent HumanComputer Interaction
 PROC. OF THE IEEE
, 2002
"... This paper describes technology and tools for intelligent humancomputer interaction (IHCI) where human cognitive, perceptual, motor, and affective factors are modeled and used to adapt the HC interface. IHCI emphasizes that human behavior encompasses both apparent human behavior and the hidden me ..."
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Cited by 19 (0 self)
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This paper describes technology and tools for intelligent humancomputer interaction (IHCI) where human cognitive, perceptual, motor, and affective factors are modeled and used to adapt the HC interface. IHCI emphasizes that human behavior encompasses both apparent human behavior and the hidden mental state behind behavioral performance. IHCI expands on the interpretation of human activities, known as W4 (what, where, when, who). While W4 only addresses the apparent perceptual aspect of human behavior, the W5+ technology for IHCI described in this paper addresses also the why and how questions, whose solution requires recognizing specific cognitive states. IHCI integrates parsing and interpretation of nonverbal information with a computational cognitive model of the user, which, in turn, feeds into processes that adapt the interface to enhance operator performance and provide for rational decisionmaking. The technology proposed is based on a general fourstage interactive framework, which moves from parsing the raw sensorymotor input, to interpreting the user's motions and emotions, to building an understanding of the user's current cognitive state. It then diagnoses various problems in the situation and adapts the interface appropriately. The interactive component of the system improves processing at each stage. Examples of perceptual, behavioral, and cognitive tools are described throughout the paper. Adaptive and intelligent HCI are important for novel applications of computing, including ubiquitous and humancentered computing
Nonlinear Diffusion ScaleSpaces: From the Continuous to the Discrete Setting
, 1996
"... A survey on continuous, semidiscrete and discrete wellposedness and scalespace results for a class of nonlinear diffusion filters is presented. This class does not require any monotony assumption (comparison principle) and, thus, allows image restoration as well. The theoretical results include ex ..."
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Cited by 19 (8 self)
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A survey on continuous, semidiscrete and discrete wellposedness and scalespace results for a class of nonlinear diffusion filters is presented. This class does not require any monotony assumption (comparison principle) and, thus, allows image restoration as well. The theoretical results include existence, uniqueness, continuous dependence on the initial image, maximumminimum principles, average grey level invariance, smoothing Lyapunov functionals, and convergence to a constant steady state. Keywords. scalespace, nonlinear diffusion, discrete smoothing transformations. 1 Introduction In the last years nonlinear diffusion filtering has been established as a successful tool for image smoothing and restoration. Strict scalespace results have been found recently for the continuous case [16]. The goal of the present paper is to outline how they can be extended to the semidiscrete and discrete setting. This is of significant practical importance, since a scalespace representation cann...
Accurate Optical Flow in Noisy Image Sequences
, 2001
"... Optical Flow estimation in noisy image sequences requires a special denoising strategy. Towards this end we introduce a new tensordriven anisotropic diffusion scheme which is designed to enhance opticalflowlike spatiotemporal structures. This is achieved by selecting diffusivities in a special ma ..."
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Cited by 15 (3 self)
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Optical Flow estimation in noisy image sequences requires a special denoising strategy. Towards this end we introduce a new tensordriven anisotropic diffusion scheme which is designed to enhance opticalflowlike spatiotemporal structures. This is achieved by selecting diffusivities in a special manner depending on the eigenvalues of the well known structure tensor. We illustrate how the proposed choice differs from edge and coherenceenhancing anisotropic diffusion. Furthermore we extend a recently discovered discretization scheme for anisotropic diffusion to 3D data. An automatic stop criterion to terminate the diffusion after a suitable time is given. The performance of the introduced method is examined quantitatively using image sequences with a substantial amount of noise added. 1.
Discrete Wavelet Analysis for Fast Optic Flow Computation
 Applied and Computational Harmonic Analysis
, 1999
"... This paper describes a new way to compute the optic flow, based on a discrete wavelet basis analysis. The optic flow is estimated locally by the projection of the differential optic flow equation onto wavelets. The resulting linear systems are small and of fixed size (35 equations). They are solved ..."
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Cited by 14 (0 self)
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This paper describes a new way to compute the optic flow, based on a discrete wavelet basis analysis. The optic flow is estimated locally by the projection of the differential optic flow equation onto wavelets. The resulting linear systems are small and of fixed size (35 equations). They are solved to find out the visual displacement. In this way, we circumvent the classical problems of time aliasing and aperture. Moreover, the coefficients of the systems can be computed with a set of wavelet transforms, and the resolution of these systems is of similar complexity. The algorithm has thus a complexity of only O(N) (if one image of the sequence has N pixels). We show that our approach permits the measurement of illumination changes, making the optic flow computation more robust. A consistency result is also proven, which states that this method provides asymptotically correct flow estimates. Keywords Analytic wavelets, Image compression, Optic flow, Illumination, Discrete wavelets. Int...
ImageBased Hair Capture by Inverse Lighting
, 2002
"... We introduce an imagebased method for modeling a specific subject's hair. The principle of the approach is to study the variations of hair illumination under controlled illumination. The use of a stationary viewpoint and the assumption that the subject is still allows us to work with perfectly ..."
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Cited by 13 (4 self)
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We introduce an imagebased method for modeling a specific subject's hair. The principle of the approach is to study the variations of hair illumination under controlled illumination. The use of a stationary viewpoint and the assumption that the subject is still allows us to work with perfectly registered images: all pixels in an image sequence represent the same portion of the hair, and the particular illumination profile observed at each pixel can be used to infer the missing degree of directional information. This is accomplished by synthesizing reflection profiles using a hair reflectance model, for a number of candidate directions at each pixel, and choosing the orientation that provides the best profile match. Our results demonstrate the potential of this approach, by effectively reconstructing accurate hair strands that are well highlighted by a particular light source movement.