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68
Viewpoint invariant texture matching and wide baseline stereo
 in Proc. International Conference on Computer Vision
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Computing Local Surface Orientation and Shape from Texture for Curved Surfaces
, 1997
"... Shape from texture is best analyzed in two stages, analogous to stereopsis and structure from motion: (a) Computing the `texture distortion' from the image, and (b) Interpreting the `texture distortion' to infer the orientation and shape of the surface in the scene. We model the texture di ..."
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Cited by 90 (4 self)
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Shape from texture is best analyzed in two stages, analogous to stereopsis and structure from motion: (a) Computing the `texture distortion' from the image, and (b) Interpreting the `texture distortion' to infer the orientation and shape of the surface in the scene. We model the texture distortion for a given point and direction on the image plane as an affine transformation and derive the relationship between the parameters of this transformation and the shape parameters. We have developed a technique for estimating affine transforms between nearby image patches which is based on solving a system of linear constraints derived from a differential analysis. One need not explicitly identify texels or make restrictive assumptions about the nature of the texture such as isotropy. We use nonlinear minimization of a least squares error criterion to recover the surface orientation (slant and tilt) and shape (principal curvatures and directions) based on the estimated affine transforms in a number of different directions. A simple linear algorithm based on singular value decomposition of the linear parts of the affine transforms provides the initial guess for the minimization procedure. Experimental results on both planar and curved surfaces under perspective projection demonstrate good estimates for both orientation and shape. A sensitivity analysis yields predictions for both computer vision algorithms and human perception of shape from texture.
Canonical Frames for Planar Object Recognition
, 1992
"... We present a canonical frame construction for determining projectively invariant indexing functions for nonalgebraic smooth plane curves. These invariants are semilocal rather than global, which promotes tolerance to occlusion. Two applications are demonstrated. Firstly, we report preliminary work ..."
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Cited by 60 (10 self)
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We present a canonical frame construction for determining projectively invariant indexing functions for nonalgebraic smooth plane curves. These invariants are semilocal rather than global, which promotes tolerance to occlusion. Two applications are demonstrated. Firstly, we report preliminary work on building a model based recognition system for planar objects. We demonstrate that the invariant measures, derived from the canonical frame, provide sufficient discrimination between objects to be useful for recognition. Recognition is of partially occluded objects in cluttered scenes. Secondly, jigsaw puzzles are assembled and rendered from a single strongly perspective view of the separate pieces. Both applications require no camera calibration or pose information, and models are generated and verified directly from images.
Direct Computation of Shape Cues Using ScaleAdapted Spatial Derivative Operators
 International Journal of Computer Vision
, 1996
"... This paper addresses the problem of computing cues to the threedimensional structure of surfaces in the world directly from the local structure of the brightness pattern of either a single monocular image or a binocular image pair. It is shown that starting from Gaussian derivatives of order up to ..."
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Cited by 59 (9 self)
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This paper addresses the problem of computing cues to the threedimensional structure of surfaces in the world directly from the local structure of the brightness pattern of either a single monocular image or a binocular image pair. It is shown that starting from Gaussian derivatives of order up to two at a range of scales in scalespace, local estimates of (i) surface orientation from monocular texture foreshortening, (ii) surface orientation from monocular texture gradients, and (iii) surface orientation from the binocular disparity gradient can be computed without iteration or search, and by using essentially the same basic mechanism. The methodology is based on a multiscale descriptor of image structure called the windowed second moment matrix, which is computed with adaptive selection of both scale levels and spatial positions. Notably, this descriptor comprises two scale parameters; a local scale parameter describing the amount of smoothing used in derivative computations, and a...
Shapeadapted smoothing in estimation of 3D shape cues from affine distortions of local 2D brightness structure
, 2001
"... This article describes a method for reducing the shape distortions due to scalespace smoothing that arise in the computation of 3D shape cues using operators (derivatives) de ned from scalespace representation. More precisely, we are concerned with a general class of methods for deriving 3D shap ..."
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Cited by 56 (3 self)
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This article describes a method for reducing the shape distortions due to scalespace smoothing that arise in the computation of 3D shape cues using operators (derivatives) de ned from scalespace representation. More precisely, we are concerned with a general class of methods for deriving 3D shape cues from 2D image data based on the estimation of locally linearized deformations of brightness patterns. This class
Shape from texture from a multiscale perspective
 In Proc. 4th International Conference on Computer Vision
, 1993
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Shape from Texture without Boundaries
 In Proc. ECCV
, 2002
"... We describe a shape from texture method that constructs a maximum a posteriori estimate of surface coe#cients using only the deformation of individual texture elements. Our method does not need to use either the boundary of the observed surface or any assumption about the overall distribution of ..."
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Cited by 35 (4 self)
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We describe a shape from texture method that constructs a maximum a posteriori estimate of surface coe#cients using only the deformation of individual texture elements. Our method does not need to use either the boundary of the observed surface or any assumption about the overall distribution of elements. The method assumes that texture elements are of a limited number of types of fixed shape. We show that, with this assumption and assuming generic view and texture, each texture element yields the surface gradient unique up to a twofold ambiguity.
PLANAR SURFACE ORIENTATION FROM TEXTURE SPATIAL FREQUENCIES
, 1995
"... This paper presents a computational model and a practical algorithm for determining the threedimensional orientation of a planar surface from visual texture information. The model consists of three parts: (1) a local spatial frequency based texture representation; (2) a model describing the projec ..."
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Cited by 30 (1 self)
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This paper presents a computational model and a practical algorithm for determining the threedimensional orientation of a planar surface from visual texture information. The model consists of three parts: (1) a local spatial frequency based texture representation; (2) a model describing the projection of surface texture to image texture; and (3) a solution of the texture projection model for the surface orientation under an assumption of surface texture homogeneity. The algorithm first measures the dominant frequency at each image point using three waveletlike transforms, and then finds the surface orientation that minimizes the variance of the image frequencies' backprojections. The algorithm is tested on photographs of realworld surfaces, exhibiting an average accuracy of better than 3 ° in slant and 4 ° in tilt. The current model and algorithm are more accurate, yet substantially simpler, than earlier versions of this approach.
Integration of depth modules: stereopsis and texture
 Vision Research
, 1993
"... Global shape judgements were employed to examine the combination of stereopsis and shapefromtexture in the determination of threedimensional shape. Adding textural variations to stereograms increased perceived depth. Thus, texture was not simply vetoed by the strong stereo cue. In experiments whe ..."
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Cited by 28 (3 self)
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Global shape judgements were employed to examine the combination of stereopsis and shapefromtexture in the determination of threedimensional shape. Adding textural variations to stereograms increased perceived depth. Thus, texture was not simply vetoed by the strong stereo cue. In experiments where the depth specified by texture was incongruent with that specified by stereo, the data were well described by a weighted linear combination rule. Although only a small weight was assigned to texture, this weight was somewhat greater at a farther viewing distance. This could be a consequence of the decreased reliability of stereopsis at far viewing distances. Stereopsis Shapefromtexture Threedimensional shape perception Integration of depth cues
Shape from Texture and Contour by Weak Isotropy
 J. of Artificial Intelligence
, 1993
"... A unified framework for shape from texture and contour is proposed. It is based on the assumption that the surface markings are not systematically compressed, or formally, that they are weakly isotropic. The weak isotropy principle is based on analysis of the directional statistics of the projected ..."
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Cited by 28 (6 self)
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A unified framework for shape from texture and contour is proposed. It is based on the assumption that the surface markings are not systematically compressed, or formally, that they are weakly isotropic. The weak isotropy principle is based on analysis of the directional statistics of the projected surface markings. It builds on several previous theories, in particular by Witkin [25] and Kanatani [15]. It extends these theories in various ways, most notably to perspective projection. The theory also provides an exact solution to an estimation problem earlier solved approximately by Kanatani. The weak isotropy principle leads to a computationally efficient algorithm, WISP, for estimation of surface orientation. WISP uses simple image observables that are shown to be direct correlates of the surface orientation to compute an initial approximate estimate in a single step. In certain simple cases this first estimate is exact, and in experiments with natural images it is typically within 5...