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Now showing 1 - 10 of 18
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    An Error Bound for Decoupled Visibility with Application to Relighting
    (The Eurographics Association, 2011) Schwenk, Karsten; Fellner, Dieter W.; N. Avis and S. Lefebvre
    Monte Carlo estimation of direct lighting is often dominated by visibility queries. If an error is tolerable, the calculations can be sped up by using a simple scalar occlusion factor per light source to attenuate radiance, thus decoupling the expensive estimation of visibility from the comparatively cheap sampling of unshadowed radiance and BRDF. In this paper we analyze the error associated with this approximation and derive an upper bound. We demonstrate in a simple relighting application how our result can be used to reduce noise by introducing a controlled error if a reliable estimate of the visibility is already available.
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    Improving Shadow Map Filtering with Statistical Analysis
    (The Eurographics Association, 2011) Gumbau, Jesus; Szirmay-Kalos, László; Sbert, Mateu; Sellés, Miguel Chover; N. Avis and S. Lefebvre
    Shadow maps are widely used in real-time applications. Shadow maps cannot be filtered linearly as regular textures, thus undersampling leads to severe aliasing. This problem has been attacked by methods that transform the depth values to allow approximate linear filtering and to approaches based on statistical analysis, which suffer from light bleeding artifacts. In this paper we propose a new statistical filtering method for shadow maps, which approximates the cumulative distribution function (CDF) of depths with a power function. This approximation significantly reduces light bleeding artifacts, maintaining performance and spatial costs. Like existing techniques, the algorithm is easy to implement on the graphics hardware and is fairly scalable.
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    Realistic Simulation of Peripheral Vision Using An Aspherical Eye Model
    (The Eurographics Association, 2011) Wu, Jiaze; Zheng, Changwen; Hu, Xiaohui; Xu, Fanjiang; N. Avis and S. Lefebvre
    A novel method is proposed to accurately simulate the peripheral vision under different visual perception. An accurate aspherical schematic eye model is firstly introduced to reasonably predict the anatomical and optical properties of the human eye. This eye model is composed of the Navarro schematic eye model with aspherical surfaces as a basic model, and a corresponding accommodation model, and both these models are combined to simulate the varying refractive power of the human eye. Finally, distributed ray tracing techniques is combined with this eye model to produce a variety of visual results.
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    Motion Capture Data Completion and Denoising by Singular Value Thresholding
    (The Eurographics Association, 2011) Lai, Ranch Y. Q.; Yuen, Pong C.; Lee, Kelvin K. W.; N. Avis and S. Lefebvre
    Human motion is of high articulation and correlation.When a human motion sequence is represented by a matrix, the matrix will be approximately low-rank. This low-rank property has been used by previous manifold-based approaches such as PCA and GPLVM. Encouraging results yielded by those approaches show that the low-rank property is of interest and importance for animating human motion. However, none of those approaches explicitly exploits it for motion capture data processing. In this paper, we propose to deal with motion capture data based on recently developed low-rank matrix completion theory and algorithms. Unlike previous approaches, the proposed method relies on low-rank prior instead of motion prior. To verify it effectiveness for dealing with motion capture data, we show that incomplete human motion can be effectively reconstructed. We also demonstrate that a noisecorrupted motion can be nicely recovered.
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    Enhancing Image-Based Aging Approaches
    (The Eurographics Association, 2011) Clément, Olivier; Paquette, Eric; N. Avis and S. Lefebvre
    Modern video games and computer-animated movies exhibit extremely realistic synthetic images. To achieve such a level of realism, artists have to consider several characteristics including material appearance changes from object aging such as rust, bumps, dents, or simply dust. Since adding these details is time-consuming, several approaches have been proposed to ease the aging process and reduce related costs. In this paper, we address some problems and limitations from image based aging techniques by proposing extensions intended to widen their range of application. First, we present a new automatic positioning system that handles special orientation cases, thus increasing the overall controllability on the aging framework. Also, we propose an innovative process to better handle multiple texture colorations during the synthesis phase of image-based aging techniques.
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    Warp-based Motion Compensation for Endoscopic Kymography
    (The Eurographics Association, 2011) Schneider, David C.; Hilsmann, Anna; Eisert, Peter; N. Avis and S. Lefebvre
    Endoscopic videokymography is a method for visualizing the motion of the plica vocalis (vocal folds) for medical diagnosis. The diagnostic interpretability of a kymogram deteriorates if camera motion interferes with vocal fold motion, which is hard to avoid in practice. We propose an algorithm for compensating strong camera motion for videokymography. The approach is based on an image-based inverse warping scheme that can be stated as an optimization problem. The algorithm is parallelizable and real-time capable on the CPU. We discuss advantages of the image-based approach and address its use for approximate structure visualization of the endoscopic scene.
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    Fast Hydraulic and Thermal Erosion on GPU
    (The Eurographics Association, 2011) Jákó, Balázs; Tóth, Balázs; N. Avis and S. Lefebvre
    Computer games, simulators and many other computer graphics applications display external scenes where a realistic looking terrain is a vital part of the view. In this paper we propose a method that generates realistic virtual terrains by simulation of hydraulic and thermal erosion on a predefined heightfield. The model is designed to be executed interactively on parallel architectures like graphics processors.
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    Skimming Video Action Using Annotated 3D Surfaces
    (The Eurographics Association, 2011) Falchuk, Ben; Wu, Chung-Ying; El-Gaaly, Tarek; Vashist, Akshay; N. Avis and S. Lefebvre
    It has become all too clear that despite the ever-growing reams of available media, we face diminishing strategic returns from it unless we craft better tools that not only let us playback media but also get us quickly to media segments of most interest. Witness the everyday frustration of false positives when watching user-generated video content that, with appropriate insight, the user might have otherwise chosen not to watch. In this paper we describe a new and dramatically different new way to both summarize and interact with multimedia information in rapid, 3D, user-in-the-loop, skimming sessions. Our new interaction technique, which can accommodate object recognition algorithms, is a fusion of media summarization and 3D scene generation techniques and runs on mobile, tablet and desktops.
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    Crystal Scattering Simulation for PET on the GPU
    (The Eurographics Association, 2011) Magdics, Milán; Szirmay-Kalos, László; N. Avis and S. Lefebvre
    This paper presents a fast algorithm to simulate inter-crystal scattering to increase the accuracy of Positron Emission Tomography (PET). Theoretically, inter-crystal scattering computation would require the solution of a particle transport problem, which is quite time consuming. However, most of this calculation can be ported to a pre-processing phase, taking advantage of the fact that the structure of the detector is fixed. Pre-computing the scattering probabilities inside the crystals, the final system response is the convolution of the geometric response obtained with the assumption that crystals are ideal absorbers and the crystal transport probability matrix. This convolution is four-dimensional which poses complexity problems as the complexity of the naive convolution evaluation grows exponentially with the dimension of the domain. We use Monte Carlo method to attack the curse of dimension. We demonstrate that these techniques have just negligible overhead.
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    Volumetric plastic deformation
    (The Eurographics Association, 2011) Prados, Francisco J. R.; Salas, Alejandro J. León; Torres, Juan Carlos; N. Avis and S. Lefebvre
    Working with volumetric information is always challenging. Displaying, processing or modifying volumes requires in most cases processing a considerable part of them, if not the whole structure. Such delays might be inconvenient for applications which require fast or smooth interaction, like realistic rendering or virtual sculpting. This paper focuses on the volume sculpting paradigm. Making use of a haptic device for interaction, the solution presented here provides a smooth and physically correct force feedback. The deformation algorithm is designed to provide a fast visual response. Additionally, this method is able to operate with large volumes, since it was designed to create a progressive, and therefore, scalable simulation.