34-Issue 2

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https://diglib.eg.org/handle/10.2312/12150

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Browsing 34-Issue 2 by Subject "and texture"

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    Compressive Image Reconstruction in Reduced Union of Subspaces
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Miandji, Ehsan; Kronander, Joel; Unger, Jonas; Olga Sorkine-Hornung and Michael Wimmer
    We present a new compressed sensing framework for reconstruction of incomplete and possibly noisy images and their higher dimensional variants, e.g. animations and light-fields. The algorithm relies on a learning-based basis representation. We train an ensemble of intrinsically two-dimensional (2D) dictionaries that operate locally on a set of 2D patches extracted from the input data. We show that one can convert the problem of 2D sparse signal recovery to an equivalent 1D form, enabling us to utilize a large family of sparse solvers. The proposed framework represents the input signals in a reduced union of subspaces model, while allowing sparsity in each subspace. Such a model leads to a much more sparse representation than widely used methods such as K-SVD. To evaluate our method, we apply it to three different scenarios where the signal dimensionality varies from 2D (images) to 3D (animations) and 4D (light-fields). We show that our method outperforms state-of-the-art algorithms in computer graphics and image processing literature.
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    IlluminationCut
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Bus, Norbert; Mustafa, Nabil H.; Biri, Venceslas; Olga Sorkine-Hornung and Michael Wimmer
    We present a novel algorithm, IlluminationCut, for rendering images using the many-lights framework. It handles any light source that can be approximated with virtual point lights (VPLs) as well as highly glossy materials. The algorithm extends the Multidimensional Lightcuts technique by effectively creating an illumination-aware clustering of the product-space of the set of points to be shaded and the set of VPLs. Additionally, the number of visibility queries for each product-space cluster is reduced by using an adaptive sampling technique. Our framework is flexible and achieves around 3 - 6 times speedup over previous state-of-the-art methods.
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    Partitioned Shadow Volumes
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Gerhards, Julien; Mora, Frédéric; Aveneau, Lilian; Ghazanfarpour, Djamchid; Olga Sorkine-Hornung and Michael Wimmer
    Real-time shadows remain a challenging problem in computer graphics. In this context, shadow algorithms generally rely either on shadow mapping or shadow volumes. This paper rediscovers an old class of algorithms that build a binary space partition over the shadow volumes. For almost 20 years, such methods have received little attention as they have been considered lacking of both robustness and efficiency. We show that these issues can be overcome, leading to a simple and robust shadow algorithm. Hence we demonstrate that this kind of approach can reach a high level of performance. Our algorithm uses a new partitioning strategy which avoids any polygon clipping. It relies on a Ternary Object Partitioning tree, a new data structure used to find if an image point is shadowed. Our method works on a triangle soup and its memory footprint is fixed. Our experiments show that it is efficient and robust, including for finely tessellated models.