Horn, B. K. P. (1975). Obtaining shape from shading information. In P.H. Winston (Ed.), The psychology of computer vision. New York: McGraw Hill.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....Photo Surface Problem Retrieve the surface(s) which gives the same photo Figure 1.1: The Shape from Shading problem. pioneered by Horn who was the rst to pose the problem as that of nding the solution of a nonlinear rst order partial di erential equation called the brightness equation [18]. This initial idea was limited by the particular numerical method that was used (the method of characteristics) and was enriched by posing the problem as a variational problem [17] within which additional constrains such as those provided by occluding contours [20] can be taken into account. The ....

B.K.P. Horn. Obtaining shape from shading information. In P.H. Winston, editor, The Psychology of Computer Vision. McGraw-Hill, New York, 1975.

....shape of a surface from the brightness variations in a black and white image of that surface. The work in our eld was pioneered by Horn who was the rst to pose the problem as that of nding the solution of a nonlinear rst order partial di erential equation called the brightness equation [15]. This initial idea was limited by the particular numerical method that was used (the method of characteristics) and was enriched by posing the problem as a variational problem [14] within which additional constrains such as those provided by occluding contours [17] can be taken into account. The ....

B.K.P. Horn. Obtaining shape from shading information. In P.H. Winston, editor, The Psychology of Computer Vision. McGraw-Hill, New York, 1975.

....across the recovered surface. In addition, the image irradiance equation is a simplistic physical model since it assumes that the reflectance function is known (usually Lambertian) and is constant across the surface. Moreover, the direction of the light source must be known in advance. Horn[1] was the first to address the shape from shading problem using a characteristic strip method. The method is notoriously sensitive to image noise. To limit the problems of noise, Ikeuchi and Horn[2] search for solutions of the image irradiance equation in which the surface normals vary smoothly. ....

B. K. P. Horn,"Obtaining Shape from Shading Information," The Psychology of Machine Vision,Ed. P. H. Winston, McGraw-Hill, New York, pp 115--155 1975.

....disturbed by the speckle noise. Compared to this two modern reconstruction methods which absolutely need two SAR acquisitions, we propose in this paper the one named radarclinometry. Much more used by the robot vision community, radarclinometry is based on the principle of the shape from shading [4]. This method entirely considers radiometric information given by a single SAR image, and is perfectly well appropriated to generate satisfying elevation model of the ground. As all this existing reconstruction method, radarclinometry requires to verify constraints such as an homogeneity of the ....

B. HORN. Obtaining Shape from Shading Information. McGraw-Hill Book Company, 1975.

.... reflectance from brightness (with a known shape and illumination) illumination from brightness (with a known shape and reflectance) The first two kinds of analyses, shape from brightness and reflectance from brightness, have been intensively studied using the shape from shading method [4, 7, 8, 18], as well as through reflectance analysis research [1, 9, 11, 13, 16, 22] In contrast, relatively limited amounts of research have been conducted in the third area, illumination frombrightness [3, 7, 12, 15, 17, 19, 25] This is because real scenes usually include both direct and indirect ....

B. K. P. Horn, "Obtaining shape from shading information," Chapter 4inThe psychlogy of Computer Vision, McGraw-Hill Book Co., New York, N.Y., 1975.

....where the surface normals are parallel to the image plane is called the occluding contour. The occluding contour provides vital information because the gradient is known on this curve. This information is used by many shape from shading algorithms as a means to initialize an iterative solution [6, 17, 20, 23, 36]. However, depending on the direction of the light source, the occluding contour can be obscured from view by self shadowing. Points lie on the self shadowed boundary if the surface normals at these points form a 90 degree angle with the light source. The problem at these points is that the ....

....that the occluding contour is available. However, depending on the orientation of the light source, occluding contour determination is not trivial. This is a problem that has not been addressed in the literature but will be studied in this research work. 2. 3 Shape From Shading Algorithms Horn [17] was the first to attempt to solve the shape from shading problem. His solution, which employs standard calculus, is called the characteristic strip method. More recently, a new algorithm similar in nature to the characteristic strip method was proposed by Bruckstein [7] These methods suffer from ....

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B. Horn. Obtaining Shape From Shading Information, chapter 4. The Psychology of Computer Vision. McGraw-Hill, 1975.

....Neuroinformatics, Computer Science Bielefeld University, POB 100 131 D 33501 Bielefeld, FRG helge techfak.uni bielefeld.de Abstract. Curvature has been identified as an important feature to reconstruct properties like object shape or relative depth from twodimensional gray scale images [6, 9]. This coincides with the assumption that curvature is processed by a separate channel in human early vision, just like contours or contrast [23, 2, 3] The process of early vision is assumed to be divided into vision modules [15] that are evaluated independently in almost completely separate ....

.... or motion are evaluated independently in almost completely separate pathways [21, 5, 10] Curvature is supposed to be processed by such a separate channel in early vision, too [23, 2, 3] Methods to reconstruct a three dimensional scene from single features are known as shape from X methods [6, 8, 1, 9]. Usually, they lead to so called illposed problems since the mapping of a three dimensional image onto a gray scale (contour, texture, image has no unique inversion. A well known approach to deal with this problem is called regularization. It removes the non uniqueness by imposing a ....

B.K.P. Horn. Obtaining shape from shading information. In P. H. Winston, editor, The Psychology of Computer Vision. McGraw-Hill, NewYork, 1975.

....the 3# shape of the imaged objects dicult. Therefore, the extraction of a 3# description from an image involves an inference process. There is a broad literature on a set of techniques for inferring such information based on explicit reconstruction of the 3# shape. These include shape from shading [1, 2, 3, 4], shape from texture [5, 6, 7, 8] shape from motion [9] shape from stereo [10, 11] and many other similar processes collectively referred to as shape from X. While these algorithms are gaining mathematical rigor [9] they still lack the robustness that is necessary to be useful in a general ....

B. K. P. Horn. Obtaining shape from shading information. In Shape from Shading, pages 123-173. The MIT Press, Cambridge, Massachusetts, 1989.

....methods have been grouped under the name shape from X . In this section, we compare the various shape from shadows methods discussed above 30 with Marr s work on shape from stereo [ Marr and Poggio 1976 ] Ullman s work on shape from motion [ Ullman 1979 ] Horn s work on shape from shading [ Horn 1989 ] Stevens work on shape from contour [ Stevens 1981 ] and Witkin s work on shape from texture [ Witkin 1981 ] Where appropriate, we discuss other work which overcome some of the problems of these earlier efforts. We summarize the discussion in table 1.1. 1.4.1 Shape from stereo Stereo [ ....

....A surface facet is brightest when it faces a source of illumination directly. In general, the intensity of the facet in an image depends on the illumination intensity, the incident angle of illumination, the viewing angle, and the reflectance properties of the material composing the surface. Horn [ Horn 1989 ] has related these factors in his work on shape from shading. Unlike stereo or motion, this method only requires a single image to generate a reconstruction. On the other hand, this technique requires a number of restrictions. The 34 illumination must come from a single light source which is ....

Berthold P. K. Horn. Obtaining Shape from Shading Information. In Berthold P. K. Horn and Michael J. Brooks, editors, Shape from Shading. MIT Press, Cambridge, MA, 1989.

....unit surface normal of an image point is then given by the equation: n = 1 p 1 p 2 q 2 [p; q; Gamma1] T The methods proposed for computing the 2 1 2 D sketch are generally referred to as shape from methods. The inspiration for these methods is the influential early work of Horn[21] on shape from shading. Surface orientation can be computed directly from image brightness when the direction of illumination is known and surface reflectance is predominantly diffuse. Where these assumptions do not hold, alternative shape from methods are potentially applicable. For example, in ....

Horn, B.K.P., Obtaining Shape from Shading Information, The Psychology of Computer Vision, P.H. Winston (ed.), McGraw-Hill, New York, pp. 115-155, 1975.

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B.K.P. Horn. Obtaining shape from shading information. In P.H. Winston, editor, The Psychology of Computer Vision. McGraw-Hill, New York, 1975.

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Horn, B. K. P. (1975). Obtaining shape from shading information. In P.H. Winston (Ed.), The psychology of computer vision. New York: McGraw Hill.

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B. K. P. Horn, "Obtaining shape from shading information," in B. K. P. Horn and M. J. Brooks (Ed.), Shape from Shading, MIT Press, pp. 123-171, Cambridge, 1989.

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B.K.P. Horn. Obtaining shape from shading information. In P.H. Winston, editor, The Psychology of Computer Vision. McGraw-Hill, New York, 1975.

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B.K.P Horn. Obtaining shape from shading information. In P.H. Winston, editor, The Psychology of Computer Vision, pages 115--155. McGraw-Hill, New York, 1975.

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B.K.P. Horn. Obtaining shape from shading information. In P.H. Winston, editor, The Psychology of Computer Vision. McGraw-Hill, New York, 1975.

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B.K.P. Horn. Obtaining shape from shading information. In P.H. Winston, editor, The Psychology of Computer Vision. McGraw-Hill, New York, 1975.

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B. K. P. Horn, "Obtaining shape from shading information," in The Psychology of Computer Vision, P. H. Winston, ed. (McGraw-Hill, New York, 1975), pp. 115--155.

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B K P Horn. Obtaining shape from shading information. In P H Winston, editor, The Psychology of Computer Vision, pages 115--155. McGraw Hill, New York, 1975.

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B. Horn. Obtaining shape from shading information. In P. Winston, editor, The Psychology of Computer Vision. McGraw-Hill, New York, 1975.

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B.K.P. Horn. Obtaining shape from shading information. Chapter 4 in 'The Psychology of Computer Vision', Ed. P.H. Winston, McGraw-Hill Book Company, New York, pages 115--155, 1975.

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B K P Horn. Obtaining shape from shading information. In P H Winston, editor, The Psychology of Computer Vision, pages 115--155. McGraw Hill, New York, 1975.

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Horn, Berthold K. P., "Obtaining Shape from'Shading Information," in The Psychology of Machine' Vision_, ed. by'P. H. Winston, Mce, raw-Hill, 197S, ppilS_ 155.

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B. HORN, Obtaining Shape from Shading Information, McGraw-Hill Book Company, 1975.

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B. K. P. Horn. Obtaining shape from shading information. In P H Winston, editor, The Psychology of Computer Vision, pages 115--155. McGraw Hill, 1975.

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