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Pattern Analysis and Machine Intelligence, IEEE Transactions on

Issue 7 • Date Jul 1991

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Displaying Results 1 - 8 of 8
  • Surface identification using the dichromatic reflection model

    Publication Year: 1991 , Page(s): 658 - 670
    Cited by:  Papers (27)  |  Patents (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1104 KB)  

    The author describes a method based on the dichromatic reflection model for identifying object surfaces. The surface spectral reflectance function of an inhomogeneous object is described as the sum of a constant interface (specular) reflectance and a body (diffuse) reflectance under all illumination geometries. The interface component is used to estimate the spectral power distribution of the illuminant without using a reference white standard, whereas the body component is used as the principal indication of the surface identity. The body reflectance function of each surface is recovered. A method to classify the observed reflectances is developed, and an algorithm to estimate a body reflectance function, unique to each surface, from the classified reflectances is proposed. The author shows the reliability of the surface classification method and the accuracy of estimated body reflectance function View full abstract»

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  • Reflections on shading

    Publication Year: 1991 , Page(s): 671 - 679
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB)  

    It is demonstrated that mutual illumination can produce significant effects in real scenes. An example is presented to illustrate the difficulties that mutual illumination presents to shape recovery schemes. These effects are qualitatively modeled by the radiosity equation. Using the radiosity equation, the authors predict the occurrence of spectral events in the radiance, namely, discontinuities in the radiance and its derivatives. Experimental evidence establishes the validity of this approach. Mutual illumination can generate discontinuities in the derivatives of radiance unrelated to local geometry. It is argued that it is not possible to obtain veridical dense depth or normal maps from a shading analysis. However, discontinuities in radiance are tractably related to scene geometry and, moreover, can be detected View full abstract»

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  • Surface reflection: physical and geometrical perspectives

    Publication Year: 1991 , Page(s): 611 - 634
    Cited by:  Papers (123)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1884 KB)  

    Reflectance models based on physical optics and geometrical optics are studied. Specifically, the authors consider the Beckmann-Spizzichino (physical optics) model and the Torrance-Sparrow (geometrical optics) model. These two models were chosen because they have been reported to fit experimental data well. Each model is described in detail, and the conditions that determine the validity of the model are clearly stated. By studying reflectance curves predicted by the two models, the authors propose a reflectance framework comprising three components: the diffuse lobe, the specular lobe, and the specular spike. The effects of surface roughness on the three primary components are analyzed in detail View full abstract»

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  • Estimation of illuminant direction, albedo, and shape from shading

    Publication Year: 1991 , Page(s): 680 - 702
    Cited by:  Papers (121)  |  Patents (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2468 KB)  

    A robust approach to the recovery of shape from shading information is presented. Assuming uniform albedo and Lambertian surface for the imaging model, two methods for estimating the azimuth of the illuminant are presented. One is based on local estimates on smooth patches, and the other method uses shading information along image contours. The elevation of the illuminant and surface albedo are estimated from image statistics, taking into consideration the effect of self-shadowing. With the estimated reflectance map parameters, the authors then compute the surface shape using a procedure that implements the smoothness constraint by requiring the gradients of reconstructed density to be close to the gradients of the input image. The algorithm is data driven, stable, updates the surface slope and height maps simultaneously, and significantly reduces the residual errors in irradiance and integrability terms. A hierarchical implementation of the algorithm is presented. Typical results on synthetic and images are given to illustrate the usefulness of the approach View full abstract»

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  • Recovery of nonrigid motion and structure

    Publication Year: 1991 , Page(s): 730 - 742
    Cited by:  Papers (134)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1448 KB)  

    The authors introduce a physically correct model of elastic nonrigid motion. This model is based on the finite element method, but decouples the degrees of freedom by breaking down object motion into rigid and nonrigid vibration or deformation modes. The result is an accurate representation for both rigid and nonrigid motion that has greatly reduced dimensionality, capturing the intuition that nonrigid motion is normally coherent and not chaotic. Because of the small number of parameters involved, this representation is used to obtain accurate overstrained estimates of both rigid and nonrigid global motion. It is also shown that these estimates can be integrated over time by use of an extended Kalman filter, resulting in stable and accurate estimates of both three-dimensional shape and three-dimensional velocity. The formulation is then extended to include constrained nonrigid motion. Examples of tracking single nonrigid objects and multiple constrained objects are presented View full abstract»

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  • Dynamic 3D models with local and global deformations: deformable superquadrics

    Publication Year: 1991 , Page(s): 703 - 714
    Cited by:  Papers (199)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1004 KB)  

    The authors present a physically based approach to fitting complex three-dimensional shapes using a novel class of dynamic models that can deform both locally and globally. They formulate the deformable superquadrics which incorporate the global shape parameters of a conventional superellipsoid with the local degrees of freedom of a spline. The model's six global deformational degrees of freedom capture gross shape features from visual data and provide salient part descriptors for efficient indexing into a database of stored models. The local deformation parameters reconstruct the details of complex shapes that the global abstraction misses. The equations of motion which govern the behavior of deformable superquadrics make them responsive to externally applied forces. The authors fit models to visual data by transforming the data into forces and simulating the equations of motion through time to adjust the translational, rotational, and deformational degrees of freedom of the models. Model fitting experiments involving 2D monocular image data and 3D range data are presented View full abstract»

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  • Constraining object features using a polarization reflectance model

    Publication Year: 1991 , Page(s): 635 - 657
    Cited by:  Papers (65)  |  Patents (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2116 KB)  

    The authors present a polarization reflectance model that uses the Fresnel reflection coefficients. This reflectance model accurately predicts the magnitudes of polarization components of reflected light, and all the polarization-based methods presented follow from this model. The authors demonstrate the capability of polarization-based methods to segment material surfaces according to varying levels of relative electrical conductivity, in particular distinguishing dielectrics, which are nonconducting, and metals, which are highly conductive. Polarization-based methods can provide cues for distinguishing different intensity-edge types arising from intrinsic light-dark or color variations, intensity edges caused by specularities, and intensity edges caused by occluding contours where the viewing direction becomes nearly orthogonal to surface normals. Analysis of reflected polarization components is also shown to enable the separation of diffuse and specular components of reflection, unobscuring intrinsic surface detail saturated by specular glare. Polarization-based methods used for constraining surface normals are discussed View full abstract»

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  • Closed-form solutions for physically based shape modeling and recognition

    Publication Year: 1991 , Page(s): 715 - 729
    Cited by:  Papers (133)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1596 KB)  

    The authors present a closed-form, physically based solution for recovering a three-dimensional (3-D) solid model from collections of 3-D surface measurements. Given a sufficient number of independent measurements, the solution is overconstrained and unique except for rotational symmetries. The proposed approach is based on the finite element method (FEM) and parametric solid modeling using implicit functions. This approach provides both the convenience of parametric modeling and the expressiveness of the physically based mesh formulation and, in addition, can provide great accuracy at physical simulation. A physically based object-recognition method that allows simple, closed-form comparisons of recovered 3-D solid models is presented. The performance of these methods is evaluated using both synthetic range data with various signal-to-noise ratios and using laser rangefinder data View full abstract»

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The IEEE Transactions on Pattern Analysis and Machine Intelligence (TPAMI) is published monthly. Its editorial board strives to present most important research results in areas within TPAMI's scope.

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Editor-in-Chief
David A. Forsyth
University of Illinois