32-Issue 7

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https://diglib.eg.org/handle/10.2312/185

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Browsing 32-Issue 7 by Subject "Computational Geometry and Object Modeling"

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    As-Rigid-As-Possible Distance Field Metamorphosis
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Weng, Yanlin; Chai, Menglei; Xu, Weiwei; Tong, Yiying; Zhou, Kun; B. Levy, X. Tong, and K. Yin
    Widely used for morphing between objects with arbitrary topology, distance field interpolation (DFI) handles topological transition naturally without the need for correspondence or remeshing, unlike surface-based interpolation approaches. However, lack of correspondence in DFI also leads to ineffective control over the morphing process. In particular, unless the user specifies a dense set of landmarks, it is not even possible to measure the distortion of intermediate shapes during interpolation, let alone control it. To remedy such issues, we introduce an approach for establishing correspondence between the interior of two arbitrary objects, formulated as an optimal mass transport problem with a sparse set of landmarks. This correspondence enables us to compute non-rigid warping functions that better align the source and target objects as well as to incorporate local rigidity constraints to perform as-rigid-as-possible DFI. We demonstrate how our approach helps achieve flexible morphing results with a small number of landmarks.
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    Garment Modeling from a Single Image
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Zhou, Bin; Chen, Xiaowu; Fu, Qiang; Guo, Kan; Tan, Ping; B. Levy, X. Tong, and K. Yin
    Modeling of realistic garments is essential for online shopping and many other applications including virtual characters. Most of existing methods either require a multi-camera capture setup or a restricted mannequin pose. We address the garment modeling problem according to a single input image. We design an all-pose garment outline interpretation, and a shading-based detail modeling algorithm. Our method first estimates the mannequin pose and body shape from the input image. It further interprets the garment outline with an oriented facet decided according to the mannequin pose to generate the initial 3D garment model. Shape details such as folds and wrinkles are modeled by shape-from-shading techniques, to improve the realism of the garment model. Our method achieves similar result quality as prior methods from just a single image, significantly improving the flexibility of garment modeling.
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    Guided Real-Time Scanning of Indoor Objects
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Kim, Young Min; Mitra, Niloy J.; Huang, Qixing; Guibas, Leonidas; B. Levy, X. Tong, and K. Yin
    Advances in 3D acquisition devices provide unprecedented opportunities for quickly scanning indoor environments. Such raw scans, however, are often noisy, incomplete, and significantly corrupted, making semantic scene understanding difficult, if not impossible. Unfortunately, in most existing workflows, scan quality is assessed after the scanning stage is completed, making it cumbersome to correct for significant missing data by additional scanning. In this work, we present a guided real-time scanning setup, wherein the incoming 3D data stream is continuously analyzed, and the data quality is automatically assessed. While the user is scanning an object, the proposed system discovers and highlights potential missing parts, thus guiding the operator (or an autonomous robot) as where to scan next. The proposed system assesses the quality and completeness of the 3D scan data by comparing to a large collection of commonly occurring indoor man-made objects using an efficient, robust, and effective scan descriptor. We have tested the system on a large number of simulated and real setups, and found the guided interface to be effective even in cluttered and complex indoor environments.
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    Polar NURBS Surface with Curvature Continuity
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Shi, Kan-Le; Yong, Jun-Hai; Tang, Lei; Sun, Jia-Guang; Paul, Jean-Claude; B. Levy, X. Tong, and K. Yin
    Polar NURBS surface is a kind of periodic NURBS surface, one boundary of which shrinks to a degenerate polar point. The specific topology of its control-point mesh offers the ability to represent a cap-like surface, which is common in geometric modeling. However, there is a critical and challenging problem that hinders its application: curvature continuity at the extraordinary singular pole. We first propose a sufficient and necessary condition of curvature continuity at the pole. Then, we present constructive methods for the two key problems respectively: how to construct a polar NURBS surface with curvature continuity and how to reform an ordinary polar NURBS surface to curvature continuous. The algorithms only depend on the symbolic representation and operations of NURBS, and they introduce no restrictions on the degree or the knot vectors. Examples and comparisons demonstrate the applications of the curvature-continuous polar NURBS surface in hole-filling and free-shape modeling.
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    Soft Folding
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Zhu, Lifeng; Igarashi, Takeo; Mitani, Jun; B. Levy, X. Tong, and K. Yin
    We introduce soft folding, a new interactive method for designing and exploring thin-plate forms. A user specifies sharp and soft folds as two-dimensional(2D) curves on a flat sheet, along with the fold magnitude and sharpness of each. Then, based on the soft folds, the system computes the three-dimensional(3D) folded shape. Internally, the system first computes a fold field, which defines local folding operations on a flat sheet. A fold field is a generalization of a discrete fold graph in origami, replacing a graph with sharp folds with a continuous field with soft folds. Next, local patches are folded independently according to the fold field. Finally, a globally folded 3D shape is obtained by assembling the locally folded patches. This algorithm computes an approximation of 3D developable surfaces with user-defined soft folds at an interactive speed. The user can later apply nonlinear physical simulation to generate more realistic results. Experimental results demonstrated that soft folding is effective for producing complex folded shapes with controllable sharpness.