Relief extraction and editing

Bas-reliefs are widely used in the world around us, for example, on coinage, for branding products, and for sculptural decoration. Reverse engineering of reliefs—extracting existing reliefs from input surfaces—makes it possible to apply them to new items; relief editing tools allow modification of reverseengineered reliefs. This paper presents a novel approach to relief extraction based on differential coordinates, which offers advantages of speed and precise extraction. It also gives the first method in the literature specifically designed for relief editing. The base surface is estimated using normal smoothing and Poisson reconstruction, allowing a relief (which may lie on a smooth or textured input surface) to be automatically extracted by height thresholding. We also provide a range of relief editing tools, also using differential coordinates, permitting both global transformations (translation, rotation, and scaling) of the whole relief, as well as local modifications to the relief. Our ∗Corresponding author. Tel.: +86 (0)731-8457-5993; Email addresses: [email protected] (Yin Chen), [email protected] (Zhi-Quan Cheng), [email protected] (Jun Li), [email protected] (Ralph R. Martin), [email protected] (Yan-Zhen Wang), [email protected] (Yu-Kun Lai), [email protected] (Gang Dang), [email protected] (Shi-Yao Jin) Preprint submitted to Computer-Aided Design October 21, 2011 relief editing algorithm, unlike generic mesh editing algorithms, is specifically designed to preserve the geometric detail of the relief over the base surface. The effectiveness of our methods is demonstrated on various examples of real industrial interest.