37-Issue 7

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https://diglib.eg.org/handle/10.2312/2632664

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Browsing 37-Issue 7 by Subject "Computer graphics"

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    Instant Stippling on 3D Scenes
    (The Eurographics Association and John Wiley & Sons Ltd., 2018) Ma, Lei; Guo, Jianwei; Yan, Dong-Ming; Sun, Hanqiu; Chen, Yanyun; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    In this paper, we present a novel real-time approach to generate high-quality stippling on 3D scenes. The proposed method is built on a precomputed 2D sample sequence called incremental Voronoi set with blue-noise properties. A rejection sampling scheme is then applied to achieve tone reproduction, by thresholding the sample indices proportional to the inverse target tonal value to produce a suitable stipple density. Our approach is suitable for stippling large-scale or even dynamic scenes because the thresholding of individual stipples is trivially parallelizable. In addition, the static nature of the underlying sequence benefits the frame-to-frame coherence of the stippling. Finally, we propose an extension that supports stipples of varying sizes and tonal values, leading to smoother spatial and temporal transitions. Experimental results reveal that the temporal coherence and real-time performance of our approach are superior to those of previous approaches.
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    Piecewise Linear Mapping Optimization Based on the Complex View
    (The Eurographics Association and John Wiley & Sons Ltd., 2018) Golla, Björn; Seidel, Hans-Peter; Chen, Renjie; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    We present an efficient modified Newton iteration for the optimization of nonlinear energies on triangle meshes. Noting that the linear mapping between any pair of triangles is a special case of harmonic mapping, we build upon the results of Chen and Weber [CW17]. Based on the complex view of the linear mapping, we show that the Hessian of the isometric energies has a simple and compact analytic expression. This allows us to analytically project the per-element Hessians to positive semidefinite matrices for efficient Newton iteration. We show that our method outperforms state-of-the-art methods on 2D deformation and parameterization. Further, we inspect the spectra of the per triangle energy Hessians and show that given an initial mapping, simple global scaling can shift the energy towards a more convex state. This allows Newton iteration to converge faster than starting from the given initial state. Additionally, our formulations support adding an energy smoothness term to the optimization with little additional effort, which improves the mapping results such that concentrated distortions are reduced.
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    Uncut Aerial Video via a Single Sketch
    (The Eurographics Association and John Wiley & Sons Ltd., 2018) Yang, Hao; Xie, Ke; Huang, Shengqiu; Huang, Hui; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    Nowadays UAV filming is getting popular, more and more stunning aerial videos appearing online. Nonetheless, making a good uncut aerial video with only one-long-shot for the large-scale outdoor scenes is still quite challenging, no many eye-catching pieces available yet. It requires users to have both consummate drone controlling skill and good perception of filming aesthetics. If totally manual, the user has to simultaneously adjust the drone position and the mounted camera orientation during the whole flyby while trying to keep all operation changes executed smoothly. Recent research has proposed a number of planning tools for automatic or semi-automatic aerial videography, however, most requires rather complex user inputs and heavy computations. In this paper, we propose a user-friendly system designed to simplify the input and automatically generate continuous camera moves to capture compelling aerial videos that users prefer to see without any post cutting or editing. Assume a rough 2.5D scene model that includes all the regions of interest are available, users are only required to casually draw a single sketch on the 2D map. Our system will analyze this rough sketch input, compute the corresponding quality views in 3D safe flying zone, and then create a globally optimal camera trajectory passing through regions of user interest via solving a combinatorial problem. At end, we optimize the drone flying speed locally to make the resulting aerial videos more visually pleasing.