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Now showing 1 - 10 of 96
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    Example-based Interpolation and Synthesis of Bidirectional Texture Functions
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Ruiters, Roland; Schwartz, Christopher; Klein, Reinhard; I. Navazo, P. Poulin
    Bidirectional Texture Functions (BTF) have proven to be a well-suited representation for the reproduction of measured real-world surface appearance and provide a high degree of realism. We present an approach for designing novel materials by interpolating between several measured BTFs. For this purpose, we transfer concepts from existing texture interpolation methods to the much more complex case of material interpolation. We employ a separation of the BTF into a heightmap and a parallax compensated BTF to cope with problems induced by parallax, masking and shadowing within the material. By working only on the factorized representation of the parallax compensated BTF and the heightmap, it is possible to efficiently perform the material interpolation. By this novel method to mix existing BTFs, we are able to design plausible and realistic intermediate materials for a large range of different opaque material classes. Furthermore, it allows for the synthesis of tileable and seamless BTFs and finally even the generation of gradually changing materials following user specified material distribution maps.
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    Geometry and Attribute Compression for Voxel Scenes
    (The Eurographics Association and John Wiley & Sons Ltd., 2016) Dado, Bas; Kol, Timothy R.; Bauszat, Pablo; Thiery, Jean-Marc; Eisemann, Elmar; Joaquim Jorge and Ming Lin
    Voxel-based approaches are today's standard to encode volume data. Recently, directed acyclic graphs (DAGs) were successfully used for compressing sparse voxel scenes as well, but they are restricted to a single bit of (geometry) information per voxel. We present a method to compress arbitrary data, such as colors, normals, or reflectance information. By decoupling geometry and voxel data via a novel mapping scheme, we are able to apply the DAG principle to encode the topology, while using a palette-based compression for the voxel attributes, leading to a drastic memory reduction. Our method outperforms existing state-of-the-art techniques and is well-suited for GPU architectures. We achieve real-time performance on commodity hardware for colored scenes with up to 17 hierarchical levels (a 128K3 voxel resolution), which are stored fully in core.
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    Perceptually Motivated Real-Time Compression of Motion Data Enhanced by Incremental Encoding and Parameter Tuning
    (The Eurographics Association, 2013) Firouzmanesh, Amirhossein; Cheng, Irene; Basu, Anup; M.- A. Otaduy and O. Sorkine
    We address the problem of efficient real-time motion data compression considering human perception. Using incremental encoding plus a database of motion primitives for each key point, our method achieves a higher or competitive compression rate with less online overhead. Trade-off between visual quality and bandwidth usage can be tuned by varying a single threshold value. A user study was performed to measure the sensitivity of human subjects to reconstruction errors in key rotation angles. Based on these evaluations we are able to perform lossy compression on the motion data without noticeable degradation in rendered qualities. While achieving real-time performance, our technique outperforms other methods in our experiments by achieving a compression ratio exceeding 50 : 1 on regular sequences.
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    Using Webcams for Product Presentations in HTML5
    (The Eurographics Association, 2013) Borg, Mathias; Kraus, Martin; Miguel Chover and A. Augusto de Sousa
    The Media Capture and Streams API ("getUserMedia API") enables plug-in free webcam support in HTML5. This opens new ways of interacting with visualisations using open web standards. In this work, two techniques are proposed that employ the user's webcam for interactive product presentations on websites. The first technique tracks the user's face and uses its position to create the impression of a user-controlled rotation of a product by displaying a sequence of product images for different view points. The second technique uses photographs of a product with reflections of coloured patterns to render the user's webcam stream as a reflection in the product presentation. Thus, users in front of a webcam are able to see their virtual reflection in a picture of a real product in real time. Our implementation of two prototypes shows that it is technically possible to implement these features with HTML5 and JavaScript only.
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    A Virtual and Augmented Reality Course Based on Inexpensive Interaction Devices and Displays
    (The Eurographics Association, 2015) Santos, Beatriz Sousa; Dias, Paulo; Madeira, Joaquim; M. Bronstein and M. Teschner
    In the last years a plethora of affordable displays, sensors, and interaction devices has reached the market, fostering the application of Virtual and Augmented Reality to many new situations. Yet, creating such applications requires a good understanding of the field and specific technical skills typically not provided by current Computer Science and Engineering education. This paper presents a graduate level course offered to MSc. Programs in Computer and Electrical Engineering which introduces the main concepts, techniques and tools in Virtual and Augmented Reality. The aim is to provide students with enough background to understand, design, implement and test such applications. The course organization, the main issues addressed and bibliography, the sensors, interaction devices and displays used, and a sample of the practical projects are briefly described. Major issues are discussed and conclusions are drawn.
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    Compressed Multiresolution Hierarchies for High-Quality Precomputed Shadows
    (The Eurographics Association and John Wiley & Sons Ltd., 2016) Scandolo, Leonardo; Bauszat, Pablo; Eisemann, Elmar; Joaquim Jorge and Ming Lin
    The quality of shadow mapping is traditionally limited by texture resolution. We present a novel lossless compression scheme for high-resolution shadow maps based on precomputed multiresolution hierarchies. Traditional multiresolution trees can compactly represent homogeneous regions of shadow maps at coarser levels, but require many nodes for fine details. By conservatively adapting the depth map, we can significantly reduce the tree complexity. Our proposed method offers high compression rates, avoids quantization errors, exploits coherency along all data dimensions, and is well-suited for GPU architectures. Our approach can be applied for coherent shadow maps as well, enabling several applications, including high-quality soft shadows and dynamic lights moving on fixed-trajectories.
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    A Sensor Based Approach to Outdoor Illumination Estimation for Augmented Reality Applications on Mobile Devices
    (The Eurographics Association, 2013) Barreira, João; Magalhães, Luís; Bessa, Maximino; Miguel Chover and A. Augusto de Sousa
    Realistic Augmented Reality applications require integrating virtual objects in the real world in a seamless visual way. The main problem to obtain a perfect visual augmentation is rendering the virtual objects with consistent illumination. In this paper, we present a novel approach to estimate outdoor illumination for Augmented Reality applications on mobile devices based on information acquired from sensors. We use an ambient light sensor to automatically detect in real-time the scene illuminance, which is used to simulate the actual lighting conditions. As outdoor illumination is mostly dependent on the weather, we derived the sky/sun illumination parameters from the light sensor data based on the IESNA sky model. The sunlight direction is estimated based on information from the GPS, date and time of the day. The result is a practical solution for outdoor illumination estimation handling light changes under natural conditions and applying them to the rendering of virtual objects in the real scene.
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    Peripheral Retinal Image Simulation Based on Retina Shapes
    (The Eurographics Association, 2016) Dias, Catarina; Wick, Michael; Rifai, Katharina; Wahl, Siegfried; T. Bashford-Rogers and L. P. Santos
    We present a method to render the image of a scene reaching the retina, the retinal image, taking into account human offaxis optical aberrations. To this end, we consider realistic wide-angle eye models that offer an anatomical description of the refractive structures of the eye as a set of lenses and accurately reproduce the optical aberrations in the periphery. We then combine these with representative retinal shapes and with distributed ray tracing. Due to the interplay between the eye model and the curved retina, we obtain a realistic simulation of the retinal image, not only foveally but also in the periphery.
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    Implicit Formulation for SPH-based Viscous Fluids
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Takahashi, Tetsuya; Dobashi, Yoshinori; Fujishiro, Issei; Nishita, Tomoyuki; Lin, Ming C.; Olga Sorkine-Hornung and Michael Wimmer
    We propose a stable and efficient particle-based method for simulating highly viscous fluids that can generate coiling and buckling phenomena and handle variable viscosity. In contrast to previous methods that use explicit integration, our method uses an implicit formulation to improve the robustness of viscosity integration, therefore enabling use of larger time steps and higher viscosities. We use Smoothed Particle Hydrodynamics to solve the full form of viscosity, constructing a sparse linear system with a symmetric positive definite matrix, while exploiting the variational principle that automatically enforces the boundary condition on free surfaces. We also propose a new method for extracting coefficients of the matrix contributed by second-ring neighbor particles to efficiently solve the linear system using a conjugate gradient solver. Several examples demonstrate the robustness and efficiency of our implicit formulation over previous methods and illustrate the versatility of our method.
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    Eye-tracktive: Measuring Attention to Body Parts when Judging Human Motions
    (The Eurographics Association, 2015) Ennis, Cathy; Hoyet, Ludovic; O'Sullivan, Carol; B. Bickel and T. Ritschel
    Virtual humans are often endowed with human-like characteristics to make them more appealing and engaging. Motion capture is a reliable way to represent natural motion on such characters, thereby allowing a wide range of animations to be automatically created and replicated. However, interpersonal differences in actors' performances can be subtle and complex, yet have a strong effect on the human observer. Such effects can be very difficult to express quantitatively or indeed even qualitatively. We investigate two subjective human motion characteristics: attractiveness and distinctiveness. We conduct a perceptual experiment, where participants' eye movements are tracked while they rate the motions of a range of actors. We found that participants fixate mostly on the torso, regardless of gait and actor sex, and very little on the limbs. However, they self-reported that they used hands, elbows and feet in their judgments, indicating a holistic approach to the problem.