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Characterizing the Shadow Space of Camera-Light Pairs

Characterizing the Shadow Space of Camera-Light Pairs

Daniel A. Vaquero

Rogerio S. Feris

Matthew Turk

Ramesh Raskar

IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR'08)
Anchorage, Alaska, 2008

Abstract

We present a theoretical analysis for characterizing the shadows cast by a point light source given its relative position to the camera. In particular, we analyze the epipolar geometry of camera-light pairs, including unusual camera-light configurations such as light sources aligned with the camera's optical axis as well as convenient arrangements such as lights placed in the camera plane. A mathematical characterization of the shadows is derived to determine the orientations and locations of depth discontinuities when projected onto the image plane that could potentially be associated with cast shadows. The resulting theory is applied to compute a lower bound on the number of lights needed to extract all depth discontinuities from a general scene using a multiflash camera. We also provide a characterization of which discontinuities are missed and which are correctly detected by the algorithm, and a foundation for choosing an optimal light placement. Experiments with depth edges computed using two-flash setups and a four-flash setup illustrate the theory, and an additional configuration with a flash at the camera's center of projection is exploited as a solution for some degenerate cases.

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Citation

Daniel A. Vaquero, Rogerio S. Feris, Matthew Turk, and Ramesh Raskar. Characterizing the Shadow Space of Camera-Light Pairs. In IEEE Conference on Computer Vision and Pattern Recognition (CVPR'08), Anchorage, Alaska, June 2008.

BibTeX Entry

@InProceedings{VaqueroCVPR2008,
  author    = {Daniel A. Vaquero and Rogerio S. Feris and Matthew Turk and Ramesh Raskar},
  title     = {Characterizing the Shadow Space of Camera-Light Pairs},
  booktitle = {IEEE Conference on Computer Vision and Pattern Recognition (CVPR'08)},
  address   = {Anchorage, Alaska},
  month     = {June},
  year      = {2008}
}