28-Issue 8

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https://diglib.eg.org/handle/10.2312/150

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    GPU Rendering of Relief Mapped Conical Frusta
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Bhagvat, D.; Jeschke, S.; Cline, D.; Wonka, P.
    This paper proposes to use relief-mapped conical frusta (cones cut by planes) to skin skeletal objects. Based on this representation, current programmable graphics hardware can perform the rendering with only minimal communication between the CPU and GPU. A consistent definition of conical frusta including texture parametrization and a continuous surface normal is provided. Rendering is performed by analytical ray casting of the relief-mapped frusta directly on the GPU. We demonstrate both static and animated objects rendered using our technique and compare to polygonal renderings of similar quality.
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    High Dynamic Range Imaging and Low Dynamic Range Expansion for Generating HDR Content
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Banterle, Francesco; Debattista, Kurt; Artusi, Alessandro; Pattanaik, Sumanta; Myszkowski, Karol; Ledda, Patrick; Chalmers, Alan
    In the last few years, researchers in the field of High Dynamic Range (HDR) Imaging have focused on providing tools for expanding Low Dynamic Range (LDR) content for the generation of HDR images due to the growing popularity of HDR in applications, such as photography and rendering via Image-Based Lighting, and the imminent arrival of HDR displays to the consumer market. LDR content expansion is required due to the lack of fast and reliable consumer level HDR capture for still images and videos. Furthermore, LDR content expansion, will allow the re-use of legacy LDR stills, videos and LDR applications created, over the last century and more, to be widely available. The use of certain LDR expansion methods, those that are based on the inversion of Tone Mapping Operators (TMOs), has made it possible to create novel compression algorithms that tackle the problem of the size of HDR content storage, which remains one of the major obstacles to be overcome for the adoption of HDR. These methods are used in conjunction with traditional LDR compression methods and can evolve accordingly. The goal of this report is to provide a comprehensive overview on HDR Imaging, and an in depth review on these emerging topics.
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    eNVyMyCar: A Multiplayer Car Racing Game for Teaching Computer Graphics
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Ganovelli, F.; Corsini, M.
    The development of a computer game is widely used as a way of conveying concepts regarding Computer Science. There are several reasons for this: it stimulates creativity, it provides an immediate sense of achievement (when the code works), it typically covers all the aspects of an introductory course, and it is easy to find ideas just by looking around and finding stimulation from one s environment and from fellow students. In this paper we present eNVyMyCar, a framework for the collaborative/competitive development of a computer game, and report the experience of its use in two Computer Graphics courses held in 2007. We developed a multiplayer car racing game where the student s task is just to implement the rendering of the scene, while all the other aspects, communication and synchronization are implemented in the framework and are transparent to the developer. The innovative feature of our framework is that all on-line users can see the views produced by their fellow students. This motivates students to improve their work by comparing it with other students and picking up ideas from them. It also gives students an opportunity to show off to their classmates.
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    Geometry Images of Arbitrary Genus in the Spherical Domain
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Gauthier, M.; Poulin, P.
    While existing spherical parameterization algorithms are limited to genus-0 geometrical models, we believe a wide class of models of arbitrary genus can also benefit from the spherical domain. We present a complete and robust pipeline that can generate spherical geometry images from arbitrary genus surfaces where the holes are explicitly represented. The geometrical model, represented as a triangle mesh, is first made topologically equivalent to a sphere by cutting each hole along its generators, thus performing genus reduction. The resulting genus-0 model is then parameterized on the sphere, where it is resampled in a way to preserve connectivity between holes and to reduce the visual impact of seams due to these holes. Knowing the location of each pair of boundary components in parametric space, our novel sampling scheme can automatically choose to scale down or completely eliminate the associated hole, depending on geometry image resolution, thus lowering the genus of the reconstructed model. We found our method to scale better than other geometry image algorithms for higher genus models. We illustrate our approach on remeshing, level-of-detail rendering, normal mapping and topology editing.
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    Procedural Arrangement of Furniture for Real-Time Walkthroughs
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Germer, T.; Schwarz, M.
    This paper presents a procedural approach to generate furniture arrangements for large virtual indoor scenes. The interiors of buildings in 3D city scenes are often omitted. Our solution creates rich furniture arrangements for all rooms of complex buildings and even for entire cities. The key idea is to only furnish the rooms in the vicinity of the viewer while the user explores a building in real time. In order to compute the object layout we introduce an agent-based solution and demonstrate the flexibility and effectiveness of the agent approach. Furthermore, we describe advanced features of the system, like procedural furniture geometry, persistent room layouts, and styles for high-level control.
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    GIzMOs: Genuine Image Mosaics with Adaptive Tiling
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Pavic, D.; Ceumern, U.; Kobbelt, L.
    We present a method that splits an input image into a set of tiles. Each tile is then replaced by another image from a large database such that, when viewed from a distance, the original image is reproduced as well as possible. While the general concept of image mosaics is not new, we consider our results as genuine image mosaics (or short GIzMOs) in the sense that the images from the database are not modified in any way. This is different from previous work, where the image tiles are usually colour shifted or overlaid with the high-frequency content of the input image. Besides the regular alignment of the tiles we propose a greedy approach for adaptive tiling where larger tiles are placed in homogenous image regions. By this we avoid the visual periodicity, which is induced by the equal spacing of the image tiles in the completely regular setting. Our overall system addresses also the cleaning of the image database by removing all unwanted images with no meaningful content. We apply differently sophisticated image descriptors to find the best matching image for each tile. For aesthetic and artistic reasons we classify each tile as feature or non-feature and then apply a suitable image descriptor. In a user study we have verified that our descriptors lead to mosaics that are significantly better recognizable than just taking, e.g. average colour values.
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    Wipe-Off: An Intuitive Interface for Exploring Ultra-Large Multi-Spectral Data Sets for Cultural Heritage Diagnostics
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Ponto, K.; Seracini, M.; Kuester, F.
    A visual analytics technique for the intuitive, hands-on analysis of massive, multi-dimensional and multi-variate data is presented. This multi-touch-based technique introduces a set of metaphors such as wiping, scratching, sandblasting, squeezing and drilling, which allow for rapid analysis of global and local characteristics in the data set, accounting for factors such as gesture size, pressure and speed. A case study is provided for the analysis of multi-spectral image data of cultural artefacts. By aligning multi-spectral layers in a stack, users can apply different multi-touch metaphors to investigate features across different wavelengths. With this technique, flexibly definable regions can be interrogated concurrently without affecting surrounding data.
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    g-BRDFs: An Intuitive and Editable BTF Representation
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Menzel, N.; Guthe, M.
    Measured reflection data such as the bidirectional texture function (BTF) represent spatial variation under the full hemisphere of view and light directions and offer a very realistic visual appearance. Despite its high-dimensional nature, recent compression techniques allow rendering of BTFs in real time. Nevertheless, a still unsolved problem is that there is no representation suited for real-time rendering that can be used by designers to modify the BTF s appearance. For intuitive editing, a set of low-dimensional comprehensible parameters, stored as scalars, colour values or texture maps, is required. In this paper we present a novel way to represent BTF data by introducing the geometric BRDF (g-BRDF), which describes both the underlying meso- and micro-scale structure in a very compact way. Both are stored in texture maps with only a few additional scalar parameters that can all be modified at runtime and thus give the designer full control over the material s appearance in the final real-time application. The g-BRDF does not only allow intuitive editing, but also reduces the measured data into a small set of textures, yielding a very effective compression method. In contrast to common material representation combining heightfields and BRDFs, our g-BRDF is physically based and derived from direct measurement, thus representing real-world surface appearance. In addition, we propose an algorithm for fully automatic decomposition of a given measured BTF into the g-BRDF representation.
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    Replica Exchange Light Transport
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Kitaoka, Shinya; Kitamura, Yoshifumi; Kishino, Fumio
    We solve the light transport problem by introducing a novel unbiased Monte Carlo algorithm called replica exchange light transport, inspired by the replica exchange Monte Carlo method in the fields of computational physics and statistical information processing. The replica exchange Monte Carlo method is a sampling technique whose operation resembles simulated annealing in optimization algorithms using a set of sampling distributions. We apply it to the solution of light transport integration by extending the probability density function of an integrand of the integration to a set of distributions. That set of distributions is composed of combinations of the path densities of different path generation types: uniform distributions in the integral domain, explicit and implicit paths in light (particle/photon) tracing, indirect paths in bidirectional path tracing, explicit and implicit paths in path tracing, and implicit caustics paths seen through specular surfaces including the delta function in path tracing. The replica-exchange light transport algorithm generates a sequence of path samples from each distribution and samples the simultaneous distribution of those distributions as a stationary distribution by using the Markov chain Monte Carlo method. Then the algorithm combines the obtained path samples from each distribution using multiple importance sampling. We compare the images generated with our algorithm to those generated with bidirectional path tracing and Metropolis light transport based on the primary sample space. Our proposing algorithm has better convergence property than bidirectional path tracing and the Metropolis light transport, and it is easy to implement by extending the Metropolis light transport.
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    Bounding Volume Hierarchies of Slab Cut Balls
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Larsson, T.; Akenine-Moeller, T.
    We introduce a bounding volume hierarchy based on the Slab Cut Ball. This novel type of enclosing shape provides an attractive balance between tightness of fit, cost of overlap testing, and memory requirement. The hierarchy construction algorithm includes a new method for the construction of tight bounding volumes in worst case O(n) time, which means our tree data structure is constructed in O(n log A n) time using traditional top-down building methods. A fast overlap test method between two slab cut balls is also proposed, requiring as few as 28-99 arithmetic operations, including the transformation cost. Practical collision detection experiments confirm that our tree data structure is amenable for high performance collision queries. In all the tested benchmarks, our bounding volume hierarchy consistently gives performance improvements over the sphere tree, and it is also faster than the OBB tree in five out of six scenes. In particular, our method is asymptotically faster than the sphere tree, and it also outperforms the OBB tree, in close proximity situations.
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    Autostereoscopic Rendering of Multiple Light Fields
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Escriva, M.; Blasco, J.; Abad, F.; Camahort, E.; Vivo, R.
    Light fields were introduced a decade ago as a new high-dimensional graphics rendering model. However, they have not been thoroughly used because their applications are very specific and their storage requirements are too high. Recently, spatial imaging devices have been related to light fields. These devices allow several users to see three-dimensional (3D) images without using glasses or other intrusive elements.This paper presents a light-field model that can be rendered in an autostereoscopic spatial device. The model is viewpoint-independent and supports continuous multiresolution, foveal rendering, and integrating multiple light fields and geometric models in the same scene.We also show that it is possible to examine interactively a scene composed of several light fields and geometric models. Visibility is taken care of by the algorithm. Our goal is to apply our models to 3D TV and spatial imaging.
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    A Bayesian Monte Carlo Approach to Global Illumination
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Brouillat, Jonathan; Bouville, Christian; Loos, Brad; Hansen, Charles; Bouatouch, Kadi
    Most Monte Carlo rendering algorithms rely on importance sampling to reduce the variance of estimates. Importance sampling is efficient when the proposal sample distribution is well-suited to the form of the integrand but fails otherwise. The main reason is that the sample location information is not exploited. All sample values are given the same importance regardless of their proximity to one another. Two samples falling in a similar location will have equal importance whereas they are likely to contain redundant information. The Bayesian approach we propose in this paper uses both the location and value of the data to infer an integral value based on a prior probabilistic model of the integrand. The Bayesian estimate depends only on the sample values and locations, and not how these samples have been chosen. We show how this theory can be applied to the final gathering problem and present results that clearly demonstrate the benefits of Bayesian Monte Carlo.
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    A Shape Grammar for Developing Glyph-based Visualizations
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Karnick, P.; Jeschke, S.; Cline, D.; Razdan, A.; Wentz, E.; Wonka, P.
    In this paper we address the question of how to quickly model glyph-based Geographic Information System visualizations. Our solution is based on using shape grammars to set up the different aspects of a visualization, including the geometric content of the visualization, methods for resolving layout conflicts and interaction methods. Our approach significantly increases modelling efficiency over similarly flexible systems currently in use.
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    Robust and Efficient Surface Reconstruction From Range Data
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Labatut, P.; Pons, J.-P.; Keriven, R.
    We describe a robust but simple algorithm to reconstruct a surface from a set of merged range scans. Our key contribution is the formulation of the surface reconstruction problem as an energy minimisation problem that explicitly models the scanning process. The adaptivity of the Delaunay triangulation is exploited by restricting the energy to inside/outside labelings of Delaunay tetrahedra. Our energy measures both the output surface quality and how well the surface agrees with soft visibility constraints. Such energy is shown to perfectly fit into the minimum s - t cuts optimisation framework, allowing fast computation of a globally optimal tetrahedra labeling, while avoiding the shrinking bias that usually plagues graph cuts methods.The behaviour of our method confronted to noise, undersampling and outliers is evaluated on several data sets and compared with other methods through different experiments: its strong robustness would make our method practical not only for reconstruction from range data but also from typically more difficult dense point clouds, resulting for instance from stereo image matching. Our effective modeling of the surface acquisition inverse problem, along with the unique combination of Delaunay triangulation and minimum s - t cuts, makes the computational requirements of the algorithm scale well with respect to the size of the input point cloud.
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    Table of Contents and Cover
    (The Eurographics Association and Blackwell Publishing Ltd, 2009)
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    Time-Adaptive Lines for the Interactive Visualization of Unsteady Flow Data Sets
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Cuntz, N.; Pritzkau, A.; Kolb, A.
    The quest for the ideal flow visualization reveals two major challenges: interactivity and accuracy. Interactivity stands for explorative capabilities and real-time control. Accuracy is a prerequisite for every professional visualization in order to provide a reliable base for analysis of a data set. Geometric flow visualization has a long tradition and comes in very different flavors. Among these, stream, path and streak lines are known to be very useful for both 2D and 3D flows. Despite their importance in practice, appropriate algorithms suited for contemporary hardware are rare. In particular, the adaptive construction of the different line types is not sufficiently studied. This study provides a profound representation and discussion of stream, path and streak lines. Two algorithms are proposed for efficiently and accurately generating these lines using modern graphics hardware. Each includes a scheme for adaptive time-stepping. The adaptivity for stream and path lines is achieved through a new processing idea we call selective transform feedback . The adaptivity for streak lines combines adaptive time-stepping and a geometric refinement of the curve itself. Our visualization is applied, among others, to a data set representing a simulated typhoon. The storage as a set of 3D textures requires special attention. Both algorithms explicitly support this storage, as well as the use of precomputed adaptivity information.
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    Instant Caching for Interactive Global Illumination
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Debattista, K.; Dubla, P.; Banterle, F.; Santos, L.P.; Chalmers, A.
    The ability to interactively render dynamic scenes with global illumination is one of the main challenges in computer graphics. The improvement in performance of interactive ray tracing brought about by significant advances in hardware and careful exploitation of coherence has rendered the potential of interactive global illumination a reality. However, the simulation of complex light transport phenomena, such as diffuse interreflections, is still quite costly to compute in real time. In this paper we present a caching scheme, termed Instant Caching, based on a combination of irradiance caching and instant radiosity. By reutilising calculations from neighbouring computations this results in a speedup over previous instant radiosity-based approaches. Additionally, temporal coherence is exploited by identifying which computations have been invalidated due to geometric transformations and updating only those paths. The exploitation of spatial and temporal coherence allows us to achieve superior frame rates for interactive global illumination within dynamic scenes, without any precomputation or quality loss when compared to previous methods; handling of lighting and material changes are also demonstrated.
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    Erratum
    (The Eurographics Association and Blackwell Publishing Ltd, 2009)
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    Semi-Uniform Adaptive Patch Tessellation
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Dyken, C.; Reimers, M.; Seland, J.
    We present an adaptive tessellation scheme for surfaces consisting of parametric patches. The resulting tessellations are topologically uniform, yet consistent and watertight across boundaries of patches with different tessellation levels. Our scheme is simple to implement, requires little memory and is well suited for instancing, a feature available on current Graphical Processing Units that allows a substantial performance increase. We describe how the scheme can be implemented efficiently and give performance benchmarks comparing it to some other approaches.
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    Fast Four-Way Parallel Radix Sorting on GPUs
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Ha, Linh; Krueger, Jens; Silva, Claudio T.
    Efficient sorting is a key requirement for many computer science algorithms. Acceleration of existing techniques as well as developing new sorting approaches is crucial for many real-time graphics scenarios, database systems, and numerical simulations to name just a few. It is one of the most fundamental operations to organize and filter the ever growing massive amounts of data gathered on a daily basis. While optimal sorting models for serial execution on a single processor exist, efficient parallel sorting remains a challenge. In this paper, we present a hardware-optimized parallel implementation of the radix sort algorithm that results in a significant speed up over existing sorting implementations. We outperform all known General Processing Unit (GPU) based sorting systems by about a factor of two and eliminate restrictions on the sorting key space. This makes our algorithm not only the fastest, but also the first general GPU sorting solution.