Zero crossings on lines of curvature
Computer Vision, Graphics, and Image Processing
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International Journal of Computer Vision
Uniqueness in shape from shading
International Journal of Computer Vision
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IEEE Transactions on Pattern Analysis and Machine Intelligence
Shape from shading as a partially well-constrained problem
CVGIP: Image Understanding
IEEE Transactions on Pattern Analysis and Machine Intelligence
Tracking level sets by level sets: a method for solving the shape from shading problem
Computer Vision and Image Understanding
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CVPR '97 Proceedings of the 1997 Conference on Computer Vision and Pattern Recognition (CVPR '97)
A Modern Differential Geometric Approach to Shape from Shading
A Modern Differential Geometric Approach to Shape from Shading
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ISICT '04 Proceedings of the 2004 international symposium on Information and communication technologies
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This paper is concerned with the problem of identifying types of image singular points as either maxima, minima, or saddle points, especially for the case of unknown lighting direction. Singular points are defined as maximally bright points in the image whose corresponding surface normals coincide with the lighting direction. The identification of their type is the key to the global shape from shading problem, and it can be viewed as rough estimation of the object shape in itself Using photometric invariants (e.g., extrema of the image grey level profile always lie on the parabolic curves of the object surface), it is shown that the two singular points which are connected by two steepest ascent curves starting from an image saddle point usually have different signs with each other. This constrains the possible combination of the types of the singular points in the global shape from shading problem.