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Real-time view-dependent image warping to correct non-linear distortion for curved Virtual Showcase displays

COMPUTERS & GRAPHICS-UK 2003年第4期27卷 515-528页

作者： Bimber, O Fröhlich, B Schmalstieg, D Encarnaçao, LM Bauhaus Univ Weimar D-99423 Weimar Germany Vienna Univ Technol A-1040 Vienna Austria Fraunhofer Ctr Res Comp Graph Providence RI 02903 USA

We present a quadtree-based selective refinement algorithm for real-time, view-dependent image warping used to present images with mirror displays that require a non-linear predistortion. The algorithm applies two-pass rendering, and recursively generates and selectively refines the underlying image grid with locally adapted levels of detail. Each discrete level of detail is determined by computing and evaluating the displacement error on the image plane within the image space of the mirror optics. The algorithm generates and refines only those image portions that contain visible information by considering an oriented convex container of the rendered scene. While display specific details of the algorithm are explained based on the more complex case of a particular mirror display, the Virtual Showcase its general functionality is valid for other non-linear displays. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： display algorithms viewing algorithms hierarchy and geometric transformations augmented and virtual realities

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Perceptual Evaluation of Color-to-Grayscale Image Conversions

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COMPUTER GRAPHICS FORUM 2008年第7期27卷 1745-1754页

作者： Cadik, M. Czech Tech Univ CR-16635 Prague Czech Republic

Color images often have to be converted to grayscale for reproduction, artistic purposes, or for subsequent processing. Methods performing the conversion of color images to grayscale aim to retain as much information about the original color image as possible, while simultaneously producing perceptually plausible grayscale results. Recently, many methods of conversion have been proposed, but their performance has not yet been assessed. Therefore, the strengths and weaknesses of color-to-grayscale conversions are not known. In this paper, we present the results of two subjective experiments in which a total of 24 color images were converted to grayscale using seven state-of-the-art conversions and evaluated by 119 human subjects using a paired comparison paradigm. We surveyed nearly 20000 human responses and used them to evaluate the accuracy and preference of the color-to-grayscale conversions. To the best of our knowledge, the study presented in this paper is the first perceptual evaluation of color-to-grayscale conversions. Besides exposing the strengths and weaknesses of the researched methods, the aim of the study is to attain a deeper understanding of the examined field, which can accelerate the progress of color-to-grayscale conversion.

关键词： I.3.3 [Computer Graphics]: Picture/Image Generation–Display algorithms viewing algorithms I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism–Color shading shadowing and texture I.4.3 [Image Processing and Computer Vision]: Enhancement–Filtering J.4 [Social and Behavioral Sciences]: Psychology

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Visualizing Time-Specific Hurricane Predictions, with Uncertainty, from Storm Path Ensembles

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COMPUTER GRAPHICS FORUM 2015年第3期34卷 371-380页

作者： Liu, L. Mirzangar, M. Kirby, R. M. Whitaker, R. House, D. H. Clemson Univ Clemson SC 29631 USA Univ Utah Salt Lake City UT 84112 USA

The U.S. National Hurricane Center (NHC) issues advisories every six hours during the life of a hurricane. These advisories describe the current state of the storm, and its predicted path, size, and wind speed over the next five days. However, from these data alone, the question What is the likelihood that the storm will hit Houston with hurricane strength winds between 12:00 and 14:00 on Saturday? cannot be directly answered. To address this issue, the NHC has recently begun making an ensemble of potential storm paths available as part of each storm advisory. Since each path is parameterized by time, predicted values such as wind speed associated with the path can be inferred for a specific time period by analyzing the statistics of the ensemble. This paper proposes an approach for generating smooth scalar fields from such a predicted storm path ensemble, allowing the user to examine the predicted state of the storm at any chosen time. As a demonstration task, we show how our approach can be used to support a visualization tool, allowing the user to display predicted storm position - including its uncertainty - at any time in the forecast. In our approach, we estimate the likelihood of hurricane risk for a fixed time at any geospatial location by interpolating simplicial depth values in the path ensemble. Adaptivelysized radial basis functions are used to carry out the interpolation. Finally, geometric fitting is used to produce a simple graphical visualization of this likelihood. We also employ a non-linear filter, in time, to assure frame-to-frame coherency in the visualization as the prediction time is advanced. We explain the underlying algorithm and definitions, and give a number of examples of how our algorithm performs for several different storm predictions, and for two different sources of predicted path ensembles.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Picture/Image Generation&mdash viewing algorithms information visualization uncertainty ensembles hurricane prediction

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Trip Synopsis: 60km in 60sec

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COMPUTER GRAPHICS FORUM 2016年第7期35卷 107-116页

作者： Huang, H. Lischinski, D. Hao, Z. Gong, M. Christie, M. Cohen-Or, D. Shenzhen Univ Coll Comp Sci & Software Engn Shenzhen Peoples R China Shenzhen VisuCA Key Lab SIAT Shenzhen Peoples R China Hebrew Univ Jerusalem Jerusalem Israel Mem Univ Newfoundland St John NF Canada INRIA Rennes Bretagne IRISA Rennes France Tel Aviv Univ Tel Aviv Israel

Computerized route planning tools are widely used today by travelers all around the globe, while 3D terrain and urban models are becoming increasingly elaborate and abundant. This makes it feasible to generate a virtual 3D flyby along a planned route. Such a flyby may be useful, either as a preview of the trip, or as an after-the-fact visual summary. However, a naively generated preview is likely to contain many boring portions, while skipping too quickly over areas worthy of attention. In this paper, we introduce 3D trip synopsis: a continuous visual summary of a trip that attempts to maximize the total amount of visual interest seen by the camera. The main challenge is to generate a synopsis of a prescribed short duration, while ensuring a visually smooth camera motion. Using an application-specific visual interest metric, we measure the visual interest at a set of viewpoints along an initial camera path, and maximize the amount of visual interest seen in the synopsis by varying the speed along the route. A new camera path is then computed using optimization to simultaneously satisfy requirements, such as smoothness, focus and distance to the route. The process is repeated until convergence. The main technical contribution of this work is a new camera control method, which iteratively adjusts the camera trajectory and determines all of the camera trajectory parameters, including the camera position, altitude, heading, and tilt. Our results demonstrate the effectiveness of our trip synopses, compared to a number of alternatives.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Picture/Image Generation&mdash viewing algorithms

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Dynamic surfel set refinement for high-quality rendering

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COMPUTERS & GRAPHICS-UK 2004年第6期28卷 827-838页

作者： Guennebaud, G Barthe, L Paulin, V Univ Toulouse 3 IRIT CNRS F-31062 Toulouse 4 France

Splatting-based rendering techniques are currently the best choice for efficient high-quality rendering of point-based geometries. However, such techniques are not suitable for large magnification, especially when the object is under-sampled. This paper improves the rendering quality of pure splatting techniques using a fast dynamic up-sampling algorithm for point-based geometry. Our algorithm is inspired by interpolatory subdivision surfaces where the geometry is refined iteratively. At each step the refined geometry is that from the previous step enriched by a new set of points. The point insertion procedure uses three operators: a local neighborhood selection operator, a refinement operator (adding new points) and a smoothing operator. Even though our insertion procedure makes the analysis of the limit surface complicated and it does not guarantee its G(1) continuity, it remains very efficient for high-quality real-time point rendering. Indeed, while providing an increased rendering quality, especially for large magnification, our algorithm needs no other preprocessing nor any additional information beyond that used by any splatting technique. This extended version (Real-time point cloud refinement, in: Proceedings of Eurographics Symposium on Point-Based Graphic, 2004, pp. 41.) contains details on creases handling and more comparison to other smoothing operators. (C) 2004 Elsevier Ltd. All rights reserved.

关键词： 1.3.3 1.3.5 viewing algorithms curve surface solid object representations

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Visualnostics: Visual Guidance Pictograms for Analyzing Projections of High-dimensional Data

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COMPUTER GRAPHICS FORUM 2015年第3期34卷 291-300页

作者： Lehmann, Dirk J. Kemmler, Fritz Zhyhalava, Tatsiana Kirschke, Marco Theisel, Holger Univ Magdeburg Visual Comp Grp D-39106 Magdeburg Germany

The visual analysis of multivariate projections is a challenging task, because complex visual structures occur. This causes fatigue or misinterpretations, which distorts the analysis. In fact, the same projection can lead to different analysis results. We provide visual guidance pictograms to improve objectivity of the visual search. A visual guidance pictogram is an iconic visual density map encoding the visual structure of certain data properties. By using them to guide the analysis, structures in the projection can be better understood and mentally linked to properties in the data. We introduce a systematic scheme for designing such pictograms and provide a set of pictograms for standard visual tasks, such as correlation and distribution analysis, for standard projections like scatterplots, RadVis, and Star Coordinates. We conduct a study that compares the visual analysis of real data with and without the support of guidance pictograms. Our tests show that the training effort for a visual search can be decreased and the analysis bias can be reduced by supporting the user's visual search with guidance pictograms.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Picture/Image Generation&mdash viewing algorithms

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Parallel Marching Blocks: A Practical Isosurfacing Algorithm for Large Data on Many-Core Architectures

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COMPUTER GRAPHICS FORUM 2016年第3期35卷 211-220页

作者： Liu, Baoquan Clapworthy, Gordon J. Dong, Feng Wu, Enhua Univ Bedfordshire Luton Beds England Chinese Acad Sci SKLCS IOS Beijing Peoples R China Univ Macau Zhuhai Peoples R China

Interactive isosurface visualisation has been made possible by mapping algorithms to GPU architectures. However, current state-of-the-art isosurfacing algorithms usually consume large amounts of GPU memory owing to the additional acceleration structures they require. As a result, the continued limitations on available GPU memory mean that they are unable to deal with the larger datasets that are now increasingly becoming prevalent. This paper proposes a new parallel isosurface-extraction algorithm that exploits the blocked organisation of the parallel threads found in modern many-core platforms to achieve fast isosurface extraction and reduce the associated memory requirements. This is achieved by optimising thread co-operation within thread-blocks and reducing redundant computation;ultimately, an indexed triangular mesh can be produced. Experiments have shown that the proposed algorithm is much faster (up to 10x) than state-of-the-art GPU algorithms and has a much smaller memory footprint, enabling it to handle much larger datasets (up to 64x) on the same GPU.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Picture/Image Generation&mdash viewing algorithms

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Perceptual Real-Time 2D-to-3D Conversion Using Cue Fusion

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2018年第6期24卷 2037-2050页

作者： Leimkuehler, Thomas Kellnhofer, Petr Ritschel, Tobias Myszkowski, Karol Seidel, Hans-Peter MPI Informat D-66123 Saarbrucken Saarland Germany MIT CSAIL Cambridge MA 02139 USA UCL London WC1E 6BT England

We propose a system to infer binocular disparity from a monocular video stream in real-time. Different from classic reconstruction of physical depth in computer vision, we compute perceptually plausible disparity, that is numerically inaccurate, but results in a very similar overall depth impression with plausible overall layout, sharp edges, fine details and agreement between luminance and disparity. We use several simple monocular cues to estimate disparity maps and confidence maps of low spatial and temporal resolution in real-time. These are complemented by spatially-varying, appearance-dependent and class-specific disparity prior maps, learned from example stereo images. Scene classification selects this prior at runtime. Fusion of prior and cues is done by means of robust MAP inference on a dense spatio-temporal conditional random field with high spatial and temporal resolution. Using normal distributions allows this in constant-time, parallel per-pixel work. We compare our approach to previous 2D-to-3D conversion systems in terms of different metrics, as well as a user study and validate our notion of perceptually plausible disparity.

关键词： Depth cues stereo image-based rendering perceptual reasoning video analysis viewing algorithms pixel classification real-time systems

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Adaptive load balancing for raycasting of non-uniformly bricked volumes

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PARALLEL COMPUTING 2007年第6期33卷 406-419页

作者： Mueller, C. Strengert, M. Ertl, T. Univ Stuttgart Inst Visualizat & Interact Syst D-70569 Stuttgart Baden Wurttembe Germany

We describe a sort-last parallel volume rendering system based on single pass volume raycasting performed in the fragment shader unit. The architecture is aimed for displaying data sets that utilize the total distributed texture memory at interactive framerates. We use non-uniform texture bricks that are constructed and distributed by means of a kd-tree to employ object space partitioning. They are further used for implementing empty-space-skipping and a load balancing mechanism, which also makes use of the kd-tree, to increase the overall performance of the rendering system. Performance numbers are given for a mid-range GPU-cluster system consisting of eight render nodes with an Infiniband interconnection. (c) 2007 Elsevier B.V. All rights reserved.

关键词： distributed/network graphics viewing algorithms distributed applications

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Visual Analysis of Spatio-Temporal Data: Applications in Weather Forecasting

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COMPUTER GRAPHICS FORUM 2015年第3期34卷 381-390页

作者： Diehl, A. Pelorosso, L. Delrieux, C. Saulo, C. Ruiz, J. Groeller, M. E. Bruckner, S. Univ Buenos Aires RA-1053 Buenos Aires DF Argentina South Natl Univ Buenos Aires DF Argentina UMI IFAECI CNRS DCAO FCEN UBA CIMA CONICET UBA Buenos Aires DF Argentina Vienna Univ Technol Vienna Austria Univ Bergen N-5020 Bergen Norway

Weather conditions affect multiple aspects of human life such as economy, safety, security, and social activities. For this reason, weather forecast plays a major role in society. Currently weather forecasts are based on Numerical Weather Prediction (NWP) models that generate a representation of the atmospheric flow. Interactive visualization of geo-spatial data has been widely used in order to facilitate the analysis of NWP models. This paper presents a visualization system for the analysis of spatio-temporal patterns in short-term weather forecasts. For this purpose, we provide an interactive visualization interface that guides users from simple visual overviews to more advanced visualization techniques. Our solution presents multiple views that include a timeline with geo-referenced maps, an integrated webmap view, a forecast operation tool, a curve-pattern selector, spatial filters, and a linked meteogram. Two key contributions of this work are the timeline with geo-referenced maps and the curve-pattern selector. The latter provides novel functionality that allows users to specify and search for meaningful patterns in the data. The visual interface of our solution allows users to detect both possible weather trends and errors in the weather forecast model. We illustrate the usage of our solution with a series of case studies that were designed and validated in collaboration with domain experts.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Picture/Image Generation&mdash viewing algorithms I.3.6 [Computer Graphics]: Methodology and Techniques Interaction techniques&mdash I.3.8 [Computer Graphics]: Applications&mdash Weather Forecast Analysis

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