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Now showing 1 - 10 of 68
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    Discrete Element Modelling Using a Parallelised Physics Engine
    (The Eurographics Association, 2009) Longshaw, Stephen M.; Turner, Martin J.; Finch, Emma; Gawthorpe, Robert; Wen Tang and John Collomosse
    Discrete Element Modelling (DEM) is a technique used widely throughout science and engineering. It offers a convenient method with which to numerically simulate a system prone to developing discontinuities within its structure. Often the technique gets overlooked as designing and implementing a model on a scale large enough to be worthwhile can be both time consuming and require specialist programming skills. Currently there are a few notable efforts to produce homogenised software to allow researchers to quickly design and run DEMs with in excess of 1 million elements. However, these applications, while open source, are still complex in nature and require significant input from their original publishers in order for them to include new features as a researcher needs them. Recently software libraries notably from the computer gaming and graphics industries, known as physics engines, have emerged. These are designed specifically to calculate the physical movement and interaction of a system of independent rigid bodies. They provide conceptual equivalents of real world constructions with which an approximation of a realistic scenario can be quickly built. This paper presents a method to utilise the most notable of these engines, NVIDIAs PhysX, to produce a parallelised geological DEM capable of supporting in excess of a million elements.
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    BRDFLab: A general system for designing BRDFs
    (The Eurographics Association, 2009) Forés, Adrià; Pattanaik, Sumanta N.; Bosch, Carles; Pueyo, Xavier; Carlos Andujar and Javier Lluch
    This paper introduces a novel system for interactive modeling and designing of arbitrary BRDFs. The system is able to deal with BRDFs defined in a variety of forms, such as analytical models, measured data or data obtained by simulation. The system also allows designing BRDFs from scratch using a combination of different analytical lobes. Using the programmable graphics hardware, it then performs interactive display of the designed BRDF, and its rendering on objects lit by complex illumination. The system also allows the fitting of an input BRDF defined in any form to our analytical lobe combination, so that it can be efficiently evaluated with GPU based rendering. The idea behind this work is to make available a general system for designing, fitting and rendering BRDFs, that is intuitive and interactive in nature. We plan to use this as a tool for simulation and modeling of complex physically-based BRDFs, and thus provide access to a larger variety of material models to the rendering community.
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    Multimodal Visualization with Interactive Closeups
    (The Eurographics Association, 2009) Ropinski, Timo; Viola, Ivan; Biermann, Martin; Hauser, Helwig; Hinrichs, Klaus; Wen Tang and John Collomosse
    Abstract Closeups are used in illustrations to provide detailed views on regions of interest. They are integrated into the rendering of the whole structure in order to reveal their spatial context. In this paper we present the concept of interactive closeups for medical reporting. Each closeup is associated with a region of interest and may show a single modality or a desired combination of the available modalities using different visualization styles. Thus it becomes possible to visualize multiple modalities simultaneously and to support doctor-to-doctor communication on the basis of interactive multimodal closeup visualizations. We discuss how to compute a layout for 2D and 3D closeups, and how to edit a closeup configuration to prepare a presentation or a subsequent doctor-to-doctor communication. Furthermore, we introduce a GPU-based rendering algorithm, which allows to render multiple closeups at interactive frame rates. We demonstrate the application of the introduced concepts to multimodal PET/CT data sets additionally co-registered with MRI.
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    Texture Classification using Fractal Geometry for the Diagnosis of Skin Cancers
    (The Eurographics Association, 2009) Blackledge, J. M.; Dubovitskiy, D. A.; Wen Tang and John Collomosse
    We present an approach to object detection and recognition in a digital image using a classification method that is based on the application of a set of features that include fractal parameters such as the Lacunarity and Fractal Dimension. The principal issues associated with object recognition are presented and a self-learning procedure for designing a decision making engine using fuzzy logic and membership function theory considered. The methods discussed, and the 'system' developed, have a range of applications in 'machine vision' and in this publication, we focus on the development and implementation of a skin cancer screening system that can be used in a general practice by non-experts to 'filter' normal from abnormal cases so that in the latter case, a patient can be referred to a specialist. The paper provides an overview of the system design and includes a link from which interested readers can download and use a demonstration version of the system developed to date.
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    An Aliasing Theory of Shadow Mapping
    (The Eurographics Association, 2009) Zhang, Fan; Zhao, Chong; Sun, Hanqiu; Wen Tang and John Collomosse
    Shadow mapping is a popular image-based technique for real-time shadow rendering. Although numerous improvements have been made to help anti-aliasing in shadow mapping, there is a lack of mathematical tools that allow us to quantitatively analyze aliasing errors in its variants. In this paper, we establish an aliasing theory to achieve this goal. A generalized representation of aliasing errors is derived from a pure mathematical point of view. The major highlight of this representation is the ability of quantifying the aliasing error at any position for general view-light configurations. On the contrary, due to the geometric assumptions used in the computational model, previous work analyzes the aliasing only along the view direction in the simplest case where the light and view directions are orthogonal. Subsequently, as a direct application of our theory, we present a comparison of aliasing distributions in a few representative variants of perspective shadow maps. We believe that these theoretical results are useful to better understand shadow mapping, and thus inspire people to develop novel techniques in this area.
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    Interactive Earthmoving Simulation in Real-time
    (The Eurographics Association, 2009) Pla-Castells, Marta; García-Fernández, Ignacio; Gamón, Miguel A.; Martínez-Durá, Rafael; Carlos Andujar and Javier Lluch
    Virtual Reality simulators of heavy machinery are often used for training purposes. However, the complexity of terrain as a dynamical system makes the simulation of earthmoving machinery an specially challenging problem. In this paper, the architecture of an excavator simulator is described, together with the different models used to describe the behavior of the systems involved. Special attention is paid to soil dynamics and to the interaction models, including soil-wheel interaction and soil-tool interaction. The different models used are physically-based, in order to guarantee a realistic simulation and an appropriate force feedback.
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    A Haptic System for Drilling into Volume Data with Polygonal Tools
    (The Eurographics Association, 2009) Liu, Yu; Laycock, Stephen D.; Wen Tang and John Collomosse
    With the developments of volume visualization technology for complex data sets comes new challenges in terms of user interaction and information extraction. Volume haptics has proven itself to be an effective way of extracting valuable information by providing an extra sense from which to perceive three dimensional data. This paper presents a haptic system for using arbitrary polygonal tools for drilling into volume data. By using this system, users can select from a variety of virtual tools to gain continuous and smooth force feedback during the drilling of volumetric data. As the user manipulates the haptic device the tool typically only moves a small amount. By considering the locations of the data points, that are modified when drilling, a relatively small number of voxels are determined each frame which must be recomputed by a Marching Cubes algorithm.
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    Accelerating Raycasting Utilizing Volume Segmentation of Industrial CT Data
    (The Eurographics Association, 2009) Frey, Steffen; Ertl, Thomas; Wen Tang and John Collomosse
    We propose a flexible acceleration technique for raycasting targeted at industrial CT data and the context of material deficiency checking. Utilizing volume segmentation that is typically employed for object analysis, GPU raycasting can be accelerated significantly using a novel data structure that is integrated into the volume to improve the responsiveness for the interactive, visual inspection of high-resolution, high-precision data. Our acceleration approach is designed to cause no extra texture lookups and to produce only marginal computational and storage overhead. Despite the fact that the data structure is integrated into the volume, the graphics card's hardware can still be used for trilinear interpolation of density values without producing incorrect results. The presented method can further easily be utilized in combination with out-of-core approaches and distributed volume rendering schemes.
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    Mosaicos Virtuales
    (The Eurographics Association, 2009) Denia, Alberto; Ribelles, José; López, Ángeles; Carlos Andujar and Javier Lluch
    Las productoras de TV que realizan retransmisiones deportivas utilizan con bastante frecuencia tecnología que les permite añadir elementos generados por ordenador. En este artículo se presenta una técnica para crear mosaicos virtuales, simulando los mosaicos que en ocasiones el público de los estadios crea levantando pequeños trozos de cartón coloreados a los que llamamos paneles. El método que se presenta persigue tanto realismo visual como eficiencia computacional. Para conseguir el primer objetivo se ha simulado el proceso de levantamiento del mosaico, su exposición y el proceso de descenso, teniendo además en cuenta factores que influyen en su aspecto como la ausencia de público, diferencias en altura de los paneles o el ligero movimiento que cada espectador imprime sobre el panel que sujeta. Para satisfacer el segundo objetivo, el proceso de animacion del mosaico se ha codificado íntegramente en GLSL.
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    Occlusion Ratio: a new Query Parameter for GPUs
    (The Eurographics Association, 2009) Mansa, Ignacio; Amundarain, Aiert; Matey, Luis; García-Alonso, Alex; Carlos Andujar and Javier Lluch
    This work suggests improvements that can be added to current GPUs and graphic rendering APIs to increase occlusion culling performance, that is, to raise the frame rate that can be achieved using hardware occlusion queries. The proposal can be easily implemented in current GPU architectures. It extends the concept of object relevance in an image and introduces the occlusion ratio parameter. Numerical tests have been carried out using pre-processed data to demonstrate our proposal. These tests show that 800% mean frame rate improvements could be achieved if occlusion queries to the GPU would return occlusion ratio data. Moreover, in low occlusion density situations -worst cases with 60-80 percent objects visible-, results show that occlusion ratio data provides 60-400 percent improvements in the frame rate.