We present a new approach for generating global illumination renderings of hand-drawn characters using only a small set of simple annotations. Our system exploits the concept of bas-relief sculptures, making it possible to generate 3D proxies suitable for rendering without requiring side-views or extensive user input. We formulate an optimization process that automatically constructs approximate geometry sufficient to evoke the impression of a consistent 3D shape. The resulting renders provide the richer stylization capabilities of 3D global illumination while still retaining the 2D hand-drawn look-and-feel. We demonstrate our approach on a varied set of hand-drawn images and animations, showing that even in comparison to ground-truth renderings of full 3D objects, our bas-relief approximation is able to produce convincing global illumination effects, including self-shadowing, glossy reflections, and diffuse color bleeding.
Daniel Sýkora, Ladislav Kavan, Martin Čadík, Ondřej Jamriška, Alec Jacobson, Brian Whited, Maryann Simmons, Olga Sorkine-Hornung. Ink-and-Ray : Bas-Relief Meshes for Adding Global Illumination Effects to Hand-Drawn Characters. ACM Transactions on Graphics 33(2) [Presented at SIGGRAPH], 2014.
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We would like to thank Yotam Gingold for the help with perceptual experiment, Anifilm and UPP for hand-drawn images, Petr Ŝtastný for adding materials and compositing, Jan Tománek for fur, and all anonymous reviewers for their constructive comments. This research has been supported by the Technology Agency of the Czech Republic under the research program TE01020415 (V3C, Visual Computing Competence Center), by the Czech Science Foundation under research program P202/12/2413 (OPALIS), COST Action IC1005 on 'HDRi: The digital capture, storage, transmission and display of real-world lighting', Swiss National Science Foundation award 200021 137879, and ERC grant iModel (StG-2012-306877).