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Now showing 1 - 10 of 115
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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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    Multi-Domain Real-time Planning in Dynamic Environments
    (ACM SIGGRAPH / Eurographics Association, 2013) Kapadia, Mubbasir; Beacco, Alejandro; Garcia, Francisco; Reddy, Vivek; Pelechano, Nuria; Badler, Norman I.; Theodore Kim and Robert Sumner
    This paper presents a real-time planning framework for multicharacter navigation that enables the use of multiple heterogeneous problem domains of differing complexities for navigation in large, complex, dynamic virtual environments. The original navigation problem is decomposed into a set of smaller problems that are distributed across planning tasks working in these different domains. An anytime dynamic planner is used to efficiently compute and repair plans for each of these tasks, while using plans in one domain to focus and accelerate searches in more complex domains. We demonstrate the benefits of our framework by solving many challenging multi-agent scenarios in complex dynamic environments requiring space-time precision and explicit coordination between interacting agents, by accounting for dynamic information at all stages of the decision-making process.
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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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    Temporally Coherent Adaptive Sampling for Imperfect Shadow Maps
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Barák, Tomas; Bittner, Jiri; Havran, Vlastimil; Nicolas Holzschuch and Szymon Rusinkiewicz
    We propose a new adaptive algorithm for determining virtual point lights (VPL) in the scope of real-time instant radiosity methods, which use a limited number of VPLs. The proposed method is based on Metropolis-Hastings sampling and exhibits better temporal coherence of VPLs, which is particularly important for real-time applications dealing with dynamic scenes. We evaluate the properties of the proposed method in the context of the algorithm based on imperfect shadow maps and compare it with the commonly used inverse transform method. The results indicate that the proposed technique can significantly reduce the temporal flickering artifacts even for scenes with complex materials and textures. Further, we propose a novel splatting scheme for imperfect shadow maps using hardware tessellation. This scheme significantly improves the rendering performance particularly for complex and deformable scenes. We thoroughly analyze the performance of the proposed techniques on test scenes with detailed materials, moving camera, and deforming geometry.
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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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    Differential Blending for Expressive Sketch-Based Posing
    (ACM SIGGRAPH / Eurographics Association, 2013) Öztireli, A. Cengiz; Baran, Ilya; Popa, Tiberiu; Dalstein, Boris; Sumner, Robert W.; Gross, Markus; Theodore Kim and Robert Sumner
    Generating highly expressive and caricatured poses can be difficult in 3D computer animation because artists must interact with characters indirectly through complex character rigs. Furthermore, since caricatured poses often involve large bends and twists, artifacts arise with traditional skinning algorithms that are not designed to blend large, disparate rotations and cannot represent extremely large rotations. To overcome these problems, we introduce a differential blending algorithm that can successfully encode and blend large transformations, overcoming the inherent limitation of previous skeletal representations. Based on this blending method, we illustrate a sketch-based interface that supports curved bones and implements the line-of-action concept from hand-drawn animation to create expressive poses in 3D animation. By interpolating stored differential transformations across temporal keyframes, our system also generates caricatured animation. We present a detailed technical analysis of our differential blending algorithm and show several posing and animation results created using our system to demonstrate the utility of our method in practice.
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    An Area-Preserving Parametrization for Spherical Rectangles
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Ureña, Carlos; Fajardo, Marcos; King, Alan; Nicolas Holzschuch and Szymon Rusinkiewicz
    We present an area-preserving parametrization for spherical rectangles which is an analytical function with domain in the unit rectangle [0;1]2 and range in a region included in the unit-radius sphere. The parametrization preserves areas up to a constant factor and is thus very useful in the context of rendering as it allows to map random sample point sets in [0;1]2 onto the spherical rectangle. This allows for easily incorporating stratified, quasi-Monte Carlo or other sampling strategies in algorithms that compute scattering from planar rectangular emitters.
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    Relationship Descriptors for Interactive Motion Adaptation
    (ACM SIGGRAPH / Eurographics Association, 2013) Al-Asqhar, Rami Ali; Komura, Taku; Choi, Myung Geol; Theodore Kim and Robert Sumner
    This paper presents an interactive motion adaptation scheme for close interactions between skeletal characters and mesh structures, such as moving through restricted environments, and manipulating objects. This is achieved through a new spatial relationship-based representation, which describes the kinematics of the body parts by the weighted sum of translation vectors relative to points selectively sampled over the surfaces of the mesh structures. In contrast to previous discrete representations that either only handle static spatial relationships, or require offline, costly optimization processes, our continuous framework smoothly adapts the motion of a character to large updates of the mesh structures and character morphologies on-the-fly, while preserving the original context of the scene. The experimental results show that our method can be used for a wide range of applications, including motion retargeting, interactive character control and deformation transfer for scenes that involve close interactions. Our framework is useful for artists who need to design animated scenes interactively, and modern computer games that allow users to design their own characters, objects and environments.
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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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    LandSketch: A First Person Point-of-View Example-Based Terrain Modeling Approach
    (ACM, 2013) Passos, Vladimir Alves dos; Igarashi, Takeo; Levent Burak Kara and Cindy Grimm
    We present an intuitive interface for easy modeling of terrains, compatible with example-based synthesis approach. The interface consists on a picture's canvas-like screen, where the user sketches silhouettes of mountains, as he would do if drawing mountains on a piece of paper. Realistic results are achieved by combining copies of the example terrain in such a manner that matches the sketched silhouette. We use Digital Elevation Models (DEM) of real world terrains as source data, and a weighted sum function to continually combine the heights.