Areas Papers

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    A Hybrid GPU Rendering Pipeline for Alias-Free Hard Shadows
    (The Eurographics Association, 2009) Hertel, Stefan; Hormann, Kai; Westermann, Rüdiger; D. Ebert and J. Krüger
    We present a new GPU pipeline for rendering per-pixel exact shadows that are cast by point lights and parallel lights. Our approach is hybrid in that it uses kD-tree accelerated ray-tracing to determine shadow-ray intersections, and rasterization to effectively reduce both the number of shadow rays to be traversed and the number of sub-spaces to be considered along each of these rays. To achieve this we introduce conservative shadow maps, which store a conservative estimate of the first intersection with the scene for each possible shadow ray. A novel approach to build such a map is presented, which uses rasterization to compute for every shadow-map pixel the triangles intersecting this pixel. By exploiting the rasterization capacities of recent GPUs in combination with accurate ray-triangle intersection tests, we are able to efficiently compute alias-free shadows in high-resolution and spatially extended scenes where classical shadow mapping techniques have severe difficulties.
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    GPU Ray-Casting for Scalable Terrain Rendering
    (The Eurographics Association, 2009) Dick, Christian; Krüger, Jens; Westermann, Rüdiger; D. Ebert and J. Krüger
    With the ever increasing resolution of scanned elevation models, geometry throughput on the GPU is becoming a severe performance limitation in 3D terrain rendering. In this paper, we investigate GPU ray-casting as an alternative to overcome this limitation, and we demonstrate its advanced scalability compared to rasterization-based techniques. By integrating ray-casting into a tile-based GPU viewer that effectively reduces bandwidth requirements in out-of-core terrain visualization, we show that the rendering performance for large, high-resolution terrain fields can be increased significantly. We show that a screen-space error below one pixel permits piecewise constant interpolation of initial height samples. Furthermore, we exploit the texture mapping capabilities on recent GPUs to perform deferred anisotropic texture filtering, which allows for the rendering of digital elevation models and corresponding photo textures. In two key experiments we compare GPU-based ray-casting to a rasterizationbased approach in the scope of terrain rendering, and we demonstrate the scalability of the proposed ray-caster with respect to display and data resolution.
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    Visualizing Heterogeneous Utility Data: A Case for Aesthetic Design
    (The Eurographics Association, 2009) Boukhelifa, Nadia; Duke, David; D. Ebert and J. Krüger
    A map visually enfolds selected messages to a target audience. To achieve this effectively, a clear understanding of 'the message, the user and the purpose' of the map needs to be translated into successful design choices covering content, typography, style and layout. Aesthetics not only inform the local design space over which rules for visual mappings are defined, but they also offer global heuristics to ensure overall visual excellence. In the world of underground utilities where companies use maps to communicate the location of their buried services, personal, internal and sector depiction standards and guidelines have a strong influence on visual design. When the scope of a map, defined by its message, user and purpose' is overlooked, conflicts arise such as between the need for realism and schematisation. In this paper we examine the role aesthetics play in the context of the utility-sector work-flow. We discuss conflicts that arise when the scope of a map's use is not carefully considered. We give details of a case study where we have attempted to reconcile a conflict between accuracy and clarity through a clutter aesthetic. Central to this research is the observed link between data, task and aesthetics; and the question of to what extent can aesthetics be designed and incorporated algorithmically.
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    RASTeR: Simple and Efficient Terrain Rendering on the GPU
    (The Eurographics Association, 2009) Bösch, Jonas; Goswami, Prashant; Pajarola, Renato; D. Ebert and J. Krüger
    This paper introduces RASTeR, a GPU based LOD technique for interactive rendering of large terrains based on a paired multi-resolution tree structure. Our approach uses regular height-data blocks and terrain independent triangle patches, which are used to efficiently subdivide the terrain data. At run time, continuous LODs can simply be generated by tiling a limited set of triangle patches, the indices to which are pre-computed, over height-field blocks, thereby minimizing the amount of data to be transferred to the graphics card. RASTeR maintains a constant frame rate through asynchronous and a priori fetching of raw or compressed elevation and texture data. The efficiency of our method is validated by presenting experimental results on large elevation models.
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    Hybrid Ambient Occlusion
    (The Eurographics Association, 2009) Reinbothe, Christoph K.; Boubekeur, Tamy; Alexa, Marc; D. Ebert and J. Krüger
    Ambient occlusion captures a subset of global illumination effects, by computing for each point of the surface the amount of incoming light from all directions and considering potential occlusion by neighboring geometry. We introduce an approach to ambient occlusion combining object and image space techniques in a deferred shading context. It is composed of three key steps: an on-the-fly voxelization of the scene, an occlusion sampling based on this voxelization and a bilateral filtering of this sampling in screen space. The result are smoothly varying ambient terms in occluded areas at interactive frame rates without any precomputation. In particular, all computations are performed dynamically on the GPU while eliminating the problem of screen-space methods, namely ignoring geometry that is not rasterized into the Z-buffer.
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    Supporting Interactive Haptic Shaping of 3D Geologic Surfaces with Deformation Property Painting
    (The Eurographics Association, 2009) Faeth, Adam; Harding, Chris; D. Ebert and J. Krüger
    Meshes made from 3D points are used to represent many important geoscience concepts such as the surface of the earth (topography), rock strata (horizons) and faults. When creating a complex computer model, a geoscientist may need to directly manipulate the shape of such a surface to reflect conflicting information from additional data sources. We present a method that allows a geoscientist to precisely interact with these surfaces by painting the surface with colors that represent its local "malleability" (deformation property values) and to interactively deform this surface into the desired shape. Since the deformation property values create an inhomogeneous mesh, we explore several adaptations of the Generalized ChainMail algorithm to allow it to support inhomogeneous mesh deformation at interactive rates. By extending the Generalized ChainMail algorithm to use a FIFO-preserving priority queue to store the candidates awaiting deformation, we can perform inhomogeneous mesh deformations at interactive rates. We present a comparison of this FIFO-preserving priority queue with a simple priority queue and with a simple FIFO queue. Both painting and deforming are part of a larger system for haptic-visual mesh manipulation, in which we explore combinations of bimanual, touchenhanced virtual tools for interactions with 3D geoscience data.
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    Geo-Spatial Context-Aware Visualization
    (The Eurographics Association, 2009) Weiskopf, Daniel; D. Ebert and J. Krüger
    Mobile computer systems equipped with wireless communication and sensor technology-such as mobile phones with cameras-have become widely available. Context information, for example the user's current location or their physical environment, plays an increasingly important role in simplifying the interaction between users and such mobile information systems. A generic framework for federating heterogeneous spatial context models is briefly described. The federated information serves as basis for the visualization of spatially referenced data. Visualization challenges include efficient rendering on mobile devices, automatic adaptation of visualization techniques to context information, as well as consideration of the quality of context in the form of uncertainty visualization.
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    Visualization Framework for the Integration and Exploration of Heterogeneous Geospatial Data
    (The Eurographics Association, 2009) Greß, Alexander; Klein, Reinhard; D. Ebert and J. Krüger
    This paper presents an interactive visualization framework for heterogeneous geospatial data developed in context of an interdisciplinary research project that aims at the risk analysis of sea-dumped chemical weapons in the Baltic Sea. In the focus of the analysis are geophysical, hydrographical, geochemical, and biological data acquired on research cruises as well as data produced by toxic compound migration and bioaccumulation modeling. These different types of data to be visualized are represented as height fields, 2D vector maps, seismic profiles, and time-dependent scalar and vector fields. In general, these datasets are given at largely varying resolutions and geospatial extents, which makes their integration into one visualization especially challenging and requires efficient level-of-detail techniques. Furthermore, special care is taken on the appropriate integration and efficient 3D visualization of all different types of data at the same time. Several examples demonstrate the effectiveness of the resulting visualizations for collaborative analysis of the data.
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    A web-enabled Geovisual Analytics tool applied to OECD Regional Data
    (The Eurographics Association, 2009) Jern, Mikael; Brezzi, Monica; Thygesen, Lars; D. Ebert and J. Krüger
    Recent advances in web-enabled graphics technologies have the potential to make a dramatic impact on developing highly interactive Geovisual Analytics applications for the Internet. An emerging and challenging application domain is geovisualization of regional (sub-national) statistics. Higher integration driven by institutional processes and economic globalisation is eroding national borders and creating competition along regional lines in the world market. Sound information at sub-national level and benchmarking of regions across countries, therefore, has increased in importance in the policy agenda of many countries. In this paper, we introduce "OECD eXplorer" an interactive tool for analyzing and communicating gained insights and discoveries about spatial-temporal and multivariate OECD regional data. This database is a potential treasure chest for policy-makers, researchers and citizens to gain a better understanding of a region's structure and performance and to carry out analysis of territorial trends and disparities based on sound information comparable across countries. Many approaches and tools have been developed in spatial-related knowledge discovery but generally they do not scale well with dynamic visualization of larger spatial data on the Internet. In this context, we introduce a web-compliant Geovisual Analytics toolkit that supports a broad collection of functional components for analysis and validation, hypothesis generation, communicating and finally collaborating gained insights and knowledge based on a snapshot mechanism that captures, re-uses and shares task-related explorative events. An important ambition is to develop a generic highly interactive web "eXplorer" platform that can be the foundation for easy customization of similar dynamic web applications using different geographical boundaries and indicators and be publicly available. Given this global dimension, the dream of building a repository "statistical Wiki" of progress indicators, where experts and public users can use these generic tools to compare situations for two or more countries, regions or local communities, could be accomplished.
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    Preface and Table of Contents
    (The Eurographics Association, 2009) Ebert, D.; D. Ebert and J. Krüger
    Preface and Table of Contents