What is a Good Day for Outdoor Photometric Stereo?

Photometric Stereo has been explored extensively in laboratory conditions since its inception. Recently, attempts have been made at applying this technique under natural outdoor lighting. Outdoor photometric stereo presents additional challenges as one does not have control over illumination anymore. In this paper, we explore the stability of surface normals reconstructed outdoors. We present a data-driven analysis based on a large database of outdoor HDR environment maps. Given a sequence of object images and corresponding sky maps captured in a single day, we investigate natural factors that impact the uncertainty in the estimated surface normals. Quantitative evidence reveals strong dependencies between expected accuracy and the normal orientation, cloud coverage, and sun elevation. In particular, we show that partially cloudy days yield greater accuracy than sunny days with clear skies; furthermore, high sun elevation--recommended in previous work--is in fact not necessarily optimal when taking more elaborate illumination models into account.

Paper

Yannick Hold-Geoffroy, Jinsong Zhang, Paulo F. U. Gotardo, and Jean-Fran├žois Lalonde
What Is a Good Day for Outdoor Photometric Stereo?
International Conference on Computational Photography (ICCP), 2015.
[PDF pre-print, 7.6MB] [BibTeX]

Talk

You can download the slides in PDF format. Please cite the source if you use these slides in a presentation.

Code

Download the code in a ZIP file, or get it from github. For more information, please see this README file.

Data

We provide some of the HDR sky maps that were used in this paper. Please see this website.

Video

Acknowledgements

The authors gratefully acknowledge the following funding sources:

  • A generous donation from the Otis-Lalonde fund in computer vision to Yannick Hold-Geoffroy
  • NSERC Discovery GRANT RGPIN-2014-05314
  • REPARTI Strategic Network
  • New faculty startup grant from the ECE department at Laval University

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