Abstract
We present a novel method to estimate an approximation of the reflectance characteristics of optically thick, homogeneous translucent materials using only a single photograph as input. First, we approximate the diffusion profile as a linear combination of piecewise constant functions, an approach that enables a linear system minimization and maximizes robustness in the presence of suboptimal input data inferred from the image. We then fit to a smoother monotonically decreasing model, ensuring continuity on its first derivative. We show the feasibility of our approach and validate it in controlled environments, comparing well against physical measurements from previous works. Next, we explore the performance of our method in uncontrolled scenarios, where neither lighting nor geometry are known. We show that these can be roughly approximated from the corresponding image by making two simple assumptions: that the object is lit by a distant light source and that it is globally convex, allowing us to capture the visual appearance of the photographed material. Compared with previous works, our technique offers an attractive balance between visual accuracy and ease of use, allowing its use in a wide range of scenarios including off-the-shelf, single images, thus extending the current repertoire of real-world data acquisition techniques.
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- Paper presented in FMX 2012 as one of the best of EuroGraphics papers
- Paper presented in CEIG 2012 as one of the best of CGF papers
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Acknowledgements
The authors would like to thank Francho Melendez for his help producing a preliminary version of the supplementary video, plus the anonymous reviewers for their valuable comments. This research has been funded by a Marie Curie grant from the Seventh Framework Programme (grant agreement no.: 251415), the Spanish Ministry of Science and Technology (TIN2007-63025 and TIN2010-21543) and the Gobierno de Aragón (projects OTRI 2009/0411 and CTPP05/09). Jose I. Echevarria was additionally funded by a research grant from the Instituto de Investigación en Ingeniería de Aragón.