The Episolar Constraint: Monocular Shape from Shadow Correspondence

Austin Abrams, Kylia Miskell, Robert Pless; The IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2013, pp. 1407-1414

Abstract


Shadows encode a powerful geometric cue: if one pixel casts a shadow onto another, then the two pixels are colinear with the lighting direction. Given many images over many lighting directions, this constraint can be leveraged to recover the depth of a scene from a single viewpoint. For outdoor scenes with solar illumination, we term this the episolar constraint, which provides a convex optimization to solve for the sparse depth of a scene from shadow correspondences, a method to reduce the search space when finding shadow correspondences, and a method to geometrically calibrate a camera using shadow constraints. Our method constructs a dense network of nonlocal constraints which complements recent work on outdoor photometric stereo and cloud based cues for 3D. We demonstrate results across a variety of time-lapse sequences from webcams "in the wild."

Related Material


[pdf]
[bibtex]
@InProceedings{Abrams_2013_CVPR,
author = {Abrams, Austin and Miskell, Kylia and Pless, Robert},
title = {The Episolar Constraint: Monocular Shape from Shadow Correspondence},
booktitle = {The IEEE Conference on Computer Vision and Pattern Recognition (CVPR)},
month = {June},
year = {2013}
}