Papadhimitri, Thoma; Favaro, Paolo (2014). A Closed-Form, Consistent and Robust Solution to Uncalibrated Photometric Stereo Via Local Diffuse Reflectance Maxima. International Journal of Computer Vision, 107(2), pp. 139-154. Springer 10.1007/s11263-013-0665-5
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Images of an object under different illumination are known to provide strong cues about the object surface. A mathematical formalization of how to recover the normal map of such a surface leads to the so-called uncalibrated photometric stereo problem. In the simplest instance, this problem can be reduced to the task of identifying only three parameters: the so-called generalized bas-relief (GBR) ambiguity. The challenge is to find additional general assumptions about the object, that identify these parameters uniquely. Current approaches are not consistent, i.e., they provide different solutions when run multiple times on the same data. To address this limitation, we propose exploiting local diffuse reflectance (LDR) maxima, i.e., points in the scene where the normal vector is parallel to the illumination direction (see Fig. 1). We demonstrate several noteworthy properties of these maxima: a closed-form solution, computational efficiency and GBR consistency. An LDR maximum yields a simple closed-form solution corresponding to a semi-circle in the GBR parameters space (see Fig. 2); because as few as two diffuse maxima in different images identify a unique solution, the identification of the GBR parameters can be achieved very efficiently; finally, the algorithm is consistent as it always returns the same solution given the same data. Our algorithm is also remarkably robust: It can obtain an accurate estimate of the GBR parameters even with extremely high levels of outliers in the detected maxima (up to 80 % of the observations). The method is validated on real data and achieves state-of-the-art results.
|Item Type:||Journal Article (Original Article)|
|Division/Institute:||08 Faculty of Science > Institute of Computer Science (INF) > Computer Vision Group (CVG)
08 Faculty of Science > Institute of Computer Science (INF)
|UniBE Contributor:||Papadhimitri, Thoma and Favaro, Paolo|
|Subjects:||000 Computer science, knowledge & systems
500 Science > 510 Mathematics
|Date Deposited:||09 May 2014 09:42|
|Last Modified:||29 Jun 2016 13:29|
|Uncontrolled Keywords:||Photometric stereo, Uncalibrated, Diffuse, Maxima, GBR, Ambiguity|