The derivation of 3-D surface shape from shadows
Proceedings of a workshop on Image understanding workshop
Uniqueness in shape from shading
International Journal of Computer Vision
Recognition by Linear Combinations of Models
IEEE Transactions on Pattern Analysis and Machine Intelligence - Special issue on interpretation of 3-D scenes—part I
Geometric invariance in computer vision
Geometric invariance in computer vision
Geometry and photometry in three-dimensional visual recognition
Geometry and photometry in three-dimensional visual recognition
3D motion recovery via affine epipolar geometry
International Journal of Computer Vision
Singularities of Illuminated Surfaces
International Journal of Computer Vision
CVPR '97 Proceedings of the 1997 Conference on Computer Vision and Pattern Recognition (CVPR '97)
CVPR '97 Proceedings of the 1997 Conference on Computer Vision and Pattern Recognition (CVPR '97)
Shadows and shading flow fields
CVPR '96 Proceedings of the 1996 Conference on Computer Vision and Pattern Recognition (CVPR '96)
Affine Structure and Photometry
CVPR '96 Proceedings of the 1996 Conference on Computer Vision and Pattern Recognition (CVPR '96)
What is the set of images of an object under all possible lighting conditions?
CVPR '96 Proceedings of the 1996 Conference on Computer Vision and Pattern Recognition (CVPR '96)
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In a scene observed from a fixed viewpoint, the set of shadow curves in an image changes as a point light source (nearby or at infinity) assumes different locations. We show that for any finite set of point light sources illuminating an object viewed under either orthographic or perspective projection, there is an equivalence class of object shapes having the same set of shadows. Members of this equivalence class differ by a four parameter family of projective transformations, and the shadows of a transformed object are identical when the same transformation is applied to the light source locations. Under orthographic projection, this family is the generalized bas-relief (GBR) transformation, and we show that the GBR transformation is the only family of transformations of an object's shape for which the complete set of imaged shadows is identical. Furthermore, for objects with Lambertian surfaces illuminated by distant light sources, the equivalence class of object shapes which preserves shadows also preserves surface shading. Finally, we show that given multiple images under differing and unknown light source directions, it is possible to reconstruct an object's shape up to these transformations from the shadows alone.