WorldCat Identities

Nayar, Shree K.

Overview
Works: 28 works in 82 publications in 1 language and 1,126 library holdings
Genres: Conference papers and proceedings 
Roles: Author, Other, Editor
Classifications: TA1634, 006.37
Publication Timeline
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Most widely held works by Shree K Nayar
Early visual learning( Book )

8 editions published between 1996 and 1997 in English and Undetermined and held by 237 WorldCat member libraries worldwide

Computer vision : ACCV 2006 : 7th Asian Conference on Computer Vision, Hyderabad, India, January 13-16, 2006 : proceedings by P. J Narayanan( Book )

39 editions published between 2006 and 2007 in English and held by 166 WorldCat member libraries worldwide

Annotation
Implementation and evaluation of a three-dimensional photometric sampler by Hideichi Sato( Book )

3 editions published in 1992 in English and held by 6 WorldCat member libraries worldwide

An extraction algorithm uses the set of image brightness values measured at each surface point in order to compute orientation as well as the strengths of the Lambertian and specular reflection components. In order to increase the accuracy in measured orientations and reflectance parameters, we have developed a calibration method to overcome the the [sic] difference between the theoretical and the actual distributions of extended source brightness. The experimental conducted on Lambertian surfaces, specular surfaces, and hybrid surfaces show high accuracy in both estimated orientations as well as reflectance parameters. We have demonstrated the ability of our system to detect cracks, and reflectance parameter variances in several industrial objects."
Shape from interreflections by Shree K Nayar( Book )

2 editions published in 1990 in English and held by 5 WorldCat member libraries worldwide

Abstract: "All shape-from-intensity methods assume that points in a scene are only illuminated by sources of light. Most scenes consist of concave surfaces and/or concavities that result from multiple objects in the scene. In such cases, points in the scene reflect light between themselves. In the presence of these interreflections, shape-from-intensity methods produce erroneous (pseudo) estimates of shape and reflectance. The pseudo shape and reflectance estimates, however, are shown to carry information about the actual shape and reflectance of the surface. An iterative algorithm is presented that simultaneously recovers the actual shape and the actual reflectance from the pseudo estimates
Extracting shape and reflectance of lambertian, specular, and hybrid surfaces by Shree K Nayar( Book )

2 editions published in 1988 in English and held by 5 WorldCat member libraries worldwide

All existing shape extraction techniques that are based on photometric measurements rely on assumed surface reflection properties. A method is proposed for determining the shape of surfaces whose reflectance properties may vary from Lambertian to specular without prior knowledge of the relative strengths of the Lambertian and specular components of reflection. The object surface is illuminated using extended light sources and is viewed from a single direction. Surface illumination using extended sources makes it possible to ensure the detection of both Lambertian and specular reflections. Multiple source directions are used to obtain an image sequence of the object. An extraction algorithm uses the set of image intensity values measured at each surface point to compute orientation as well as the relative strengths of the Lambertian and specular reflection components. The proposed methods has been named photometric sampling as it uses samples of a photometric function that relates image intensity to surface orientation, reflectance, and light source characteristics that describes the reflectance model and orientation of a surface point. Experiments were conducted on Lambertian surfaces, specular surfaces, and hybrid surfaces whose reflectance model is composed of both Lambertian and specular components. The results show high accuracy in measured orientations and estimated reflectance parameters. Keywords: Extraction techniques; Photometric measurements; Reflectance properties; Specular reflectance; Photometric sampling
The appearance of human skin : a survey by Takanori Igarashi( Book )

4 editions published in 2007 in English and held by 5 WorldCat member libraries worldwide

Skin is the outer-most tissue of the human body. As a result, people are very aware of, and very sensitive to, the appearance of their skin. Consequently, skin appearance has been a subject of great interest in various fields of science and technology. In particular, research on skin appearance has been intensely pursued in the fields of computer graphics, computer vision, cosmetology, and medicine. In this survey, we review the most prominent results related to skin in these fields and show how these seemingly disconnected studies are related to one another. In each of the fields, the optical behaviors of specific skin components have been studied from the viewpoint of the specific objectives of the field. However, the different components of skin produce different types of optical phenomena that are determined by their physio-anatomical characteristics (sizes, shapes, and functions of the components). The final appearance of skin has contributions from complex optical interactions of many different skin components with light. In order to view these interactions in a unified manner, we describe and categorize past works based on the physiological and anatomical characteristics of the various skin components
Shape from focus by Shree K Nayar( Book )

2 editions published in 1989 in English and held by 3 WorldCat member libraries worldwide

We present two algorithms for depth estimation. The first algorithm simply looks for the focus level that maximizes the focus measure at each point. The other algorithm models the SML focus measure variations at each point as a Gaussian distribution and use this model to interpolate the computed focus measures to obtain more accurate depth estimates. The algorithms were implemented and tested using surfaces of different roughness and reflectance properties. We conclude with a brief discussion on how the proposed method can be applied to smooth textures and smooth non-textured surfaces."
Computer vision, graphics and image processing : recent advances ; [proceedings of the Indian Conference on Computer Vision, Graphics and Image Processing (ICVGIP '98) held at Indian Institute of Technology, Delhi, during December 21 - 23,1998( Book )

1 edition published in 1999 in English and held by 3 WorldCat member libraries worldwide

Proceedings of the Indian Conference on Computer Vision, Graphics and Image Processing, held at Delhi during 21-23 December 1998
Surface reflection : physical and geometrical perspectives by Shree K Nayar( Book )

2 editions published in 1989 in English and held by 3 WorldCat member libraries worldwide

Machine vision can greatly benefit from the development of accurate reflectance models. There are two approaches to the study of reflection: physical and geometrical optics. While geometrical models may be construed as mere approximations to physical models, they possess simpler mathematical forms that often render them more usable than physical models. However, geometrical models are applicable only when the wavelength of incident light is small compared to the dimensions of the surface imperfections. Therefore, it is incorrect to use these models to interpret or predict reflections from smooth surfaces, and only physical models are capable of describing the underlying reflection mechanism. This paper is directed towards unifying physical and geometrical approaches to describe reflection from surfaces that may vary from smooth to rough. More specifically, we consider the Beckmann-Spizzichino (physical optics) model and the Torrance-Sparrow (geometrical optics) model. These two models were chosen in particular as they have been reported to fit experimental data very well. Each model is described in detail, and the conditions that determine the validity of the model are clearly stated. From studying the behaviors of both models. A model is proposed comprising three reflection components: the diffuse lobe, the specular lobe, and the specular spike. The dependencies of the three components on the surface roughness and the angles of incidence and reflection are analyzed in detail
A theory of pattern rejection by Simon Baker( Book )

1 edition published in 1995 in English and held by 2 WorldCat member libraries worldwide

Abstract: "The efficiency of pattern recognition is critical when there are a large number of classes to be discriminated, or when the recognition algorithm must be applied a large number of times. We propose and analyze a general technique, namely pattern rejection, that leads to great efficiency improvements in both cases. Rejectors are introduced as algorithms that very quickly eliminate from further consideration, most of the classes or inputs (depending on the setting). Importantly, a number of rejectors may be combined to form a composite rejector, which performs far more effectively than any of its component rejectors. Composite rejectors are analyzed, and conditions derived which guarantee both efficiency and practicality. A general technique is proposed for the construction of rejectors, based on a single assumption about the pattern classes. The generality is shown through a close relationship with the Karhunen-Loev́e expansion. Further, a comparison with Fisher's discriminant analysis is included to illustrate the benefits of pattern rejection. Composite rejectors were constructed for two applications, namely, object recognition and local feature detection. In both cases, a substantial improvement in efficiency over existing techniques is demonstrated."
Parametric feature detection by Shree K Nayar( Book )

1 edition published in 1995 in English and held by 2 WorldCat member libraries worldwide

Abstract: "A large number of visual features are parametric in nature, including, [sic] edges, lines, corners, and junctions. We present a general framework for the design and implementation of detectors for parametrized features. For robustness, we argue in favor of elaborate modeling of features as they appear in the physical world. In addition, optical and sensing artifacts are incorporated to achieve realistic feature models in image domain. Each feature is represented as a densely sampled parametrized manifold in a low-dimensional subspace. During detection, the brightness distribution around each image pixel is projected to the subspace. If the projection lies close to the feature manifold, the exact location of the closest manifold point reveals the parameters of the feature. The concepts of parameter reduction by normalization, dimension reduction, pattern rejection, and efficient search are employed to achieve high efficiency. Detectors have been implemented for five specific features, namely, step edge (5 parameters), roof edge (5 parameters), line (6 parameters), corner (5 parameters), and circular disc (6 parameters). All five of these detectors were generated using the same technique by simply inputing [sic] different feature models. Detailed experiments are reported on the robustness of detection and the accuracy of parameter estimation. In the case of the step edge, our results are compared with those obtained using popular detectors. We conclude with a brief discussion on the use of relaxation to refine outputs from multiple feature detectors, and sketch a hardware architecture for a general feature detection machine."
Computer Vision-- AACV 2006 : 7th Asian Conference on Computer Vision, Hyderabad, India, January 13-16, 2006 : proceedings by Asian Conference on Computer Vision( Book )

2 editions published in 2006 in English and held by 2 WorldCat member libraries worldwide

Stereo in the presence of specular reflection by Dinkar N Bhat( Book )

1 edition published in 1994 in English and held by 2 WorldCat member libraries worldwide

Abstract: "The problem of accurate depth estimation using stereo in the presence of specular reflection is addressed. Specular relection is viewpoint dependent and can cause large intensity differences at corresponding points. Hence, mismatches can result causing significant depth errors. Current stereo algorithms largely ignore specular reflection which is a fundamental reflection phenomenon from surfaces, both smooth and rough. We analyzed the physics of specular reflection and the geometry of stereopsis which led us to an interesting relationship between stereo vergence, surface roughness, and the likelihood of a correct match. Given the lower bound on surface roughness, an optimal binocular stereo configuration can be determined which maximizes precision in depth estimation despite specular reflection. However, surface roughness is difficult to estimate in unstructured environments. Therefore, multiple view configurations independent of surface roughness are determined such that at each scene point visible to all sensors, at least one stereo pair provides a correct depth estimate. We have developed a simple algorithm to reconstruct depth from the multiple view images. Experiments with real surfaces confirm the viability of our approach. A key feature of this approach is that we do not seek to eliminate or avoid specular reflection, but rather minimize its effect on stereo matching."
Specular surfce inspection using structures highlight and gaussian images by Shree K Nayar( )

1 edition published in 1990 in English and held by 1 WorldCat member library worldwide

Polycameras: Camera Clusters for Wide Angle Imaging( )

1 edition published in 2005 in English and held by 0 WorldCat member libraries worldwide

We present the idea of a polycamera which is defined as a tightly packed camera cluster. The cluster is arranged so as to minimize the overlap between adjacent views. The objective of such clusters is to be able to image a very large field of view without loss of resolution. Since these clusters do not have a single viewpoint, analysis is provided on the effects of such non-singularities. We also present certain configurations for polycameras which cover varying fields of view. We would like to minimize the number of sensors required to capture a given field of view. Therefore we recommend the use of wide-angle sensors as opposed to traditional long focal length sensors. However, such wide-angle sensors tend to have severe distortions which pull points towards the optical center. This paper also proposes a method for recovering the distortion parameters without the use of any calibration objects. Since distortions cause straight lines in the scene to appear as curves in the image, our algorithm seeks to find the distortions parameters that would map the image curves to straight lines. The user selects a small set of points along the image curves. Recovery of the distortion parameters is formulated as the minimization of an objective function which is designed to explicitly account for noise in the selected image points. Experimental results are presented for synthetic data with different noise levels as well as for real images. Once calibrated, the image stream from a wide angle camera can be undistorted in real time using look up tables. Finally, we apply our distortion correction technique to a polycamera made of four wide-angle cameras to create a high resolution 360 degree panorama in real-time
2009 IEEE International Conference on Computational Photography, ICCP the Palace Hotel, San Francisco, CA : April 16-17, 2009 : ICCP 09 by IEEE International Conference on Computational Photography( )

2 editions published in 2009 in English and held by 0 WorldCat member libraries worldwide

Pararover: A Remote Controlled Vehicle With Omnidirectional Sensors( )

1 edition published in 1999 in English and held by 0 WorldCat member libraries worldwide

The process of teleoperation can be described as allowing a remote user to control a vehicle by interpreting sensor information captured by the vehicle. One method that is frequently used to implement teleoperation is to provide the user with a real-time video display of a perspective camera mounted on the vehicle. This method limits the remote user to seeing the environment in which is vehicle is present through the fixed viewpoint with which the camera is mounted. Having a fixed viewpoint is extremely limiting and significantly impedes the ability of the remote user to properly navigate. One way to address this problem is to mount the perspective camera on a pan-tilt device. This rarely done because it is expensive and introduces a significant increase in implementation complexity from both the mechanical and electrical point of view. With the advent of omnidirectional camera technology, there is now a second more attractive alternative. This paper describes the PARAROVER, a remote controlled vehicle constructed in the summer of 1998 to demonstrate the use of omnidirectional camera technology and a virtual reality display for vehicular teleoperational, audio-video surveillance and forward reconnaissance
 
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Audience level: 0.63 (from 0.46 for Computer V ... to 1.00 for Polycamera ...)

Computer vision : ACCV 2006 : 7th Asian Conference on Computer Vision, Hyderabad, India, January 13-16, 2006 : proceedings
Alternative Names
Shree K. Nayar Indian-American engineer

Languages
English (72)

Covers
The appearance of human skin : a surveyComputer Vision-- AACV 2006 : 7th Asian Conference on Computer Vision, Hyderabad, India, January 13-16, 2006 : proceedings