TY - CHAP A1 - Breuß, Michael A1 - Mansouri Yarahmadi, Ashkan A1 - Cunningham, Douglas W. ED - Welk, Martin ED - Urschler, Martin ED - Roth, Peter M. T1 - The Convex-Concave Ambiguity in Perspective Shape from Shading T2 - Proceedings of the OAGM Workshop 2018 Medical Image Analysis, May 15 - 16, 2018, Hall/Tyrol, Austria N2 - Shape from Shading (SFS) is a classic problem in computer vision. In recent years many perspective SFS models have been studied that yield useful SFS approaches when a photographed object is close to the camera. However, while the ambiguities inherent to the classical, orthographic SFS models are well-understood, there has been no discussion of possible ambiguities in perspective SFS models. In this paper we deal with the latter issue. Therefore we adopt a typical perspective SFS setting. We show how to transform the corresponding image irradiance equation into the format of the classical orthographic setting by employing spherical coordinates. In the latter setting we construct a convex-concave ambiguity for perspective SFS. It is to our knowledge the first time in the literature that this type of ambiguity is constructed and verified for a perspective SFS model. KW - Shape from Shading Y1 - 2018 SN - 978-3-85125-603-1 U6 - https://doi.org/10.3217/978-3-85125-603-1-13 SP - 57 EP - 63 PB - Verlag der TU Graz CY - Graz ER -