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Streaming HLODs: an out-of-core viewer for network visualization of huge polygon models

COMPUTERS & GRAPHICS-UK 2004年第1期28卷 43-50页

作者： Guthe, M Klein, R Univ Bonn Inst Comp Sci 2 D-53117 Bonn Germany

The constant growth of network and internet availability and speed as well as the increasing power of consumer level graphics hardware have created more and more interest in streaming transmission of three-dimensional data sets. However, since the size of such models is increasing even faster than the transmission or rendering bandwidth and has already exceeded the main memory available in common PCs, we present a combination of quasi view-dependent hierarchical level of detail (HLOD) rendering with priority-based streaming that is capable of rendering highly complex models at a real-time frame rates and high quality even with a low network bandwidth. We show the modifications needed to incorporate the streaming into a recent HLOD rendering system and explore different techniques to reduce the loss of quality compared to local out-of-core rendering. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： distributed/network graphics viewing algorithms compression (coding)

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Interactive Visualization of Generalized Virtual 3D City Models using Level-of-Abstraction Transitions

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COMPUTER GRAPHICS FORUM 2012年第3期31卷 885-894页

作者： Semmo, Amir Trapp, Matthias Kyprianidis, Jan Eric Doellner, Juergen Univ Potsdam Hasso Plattner Inst Potsdam Germany

Virtual 3D city models play an important role in the communication of complex geospatial information in a growing number of applications, such as urban planning, navigation, tourist information, and disaster management. In general, homogeneous graphic styles are used for visualization. For instance, photorealism is suitable for detailed presentations, and non-photorealism or abstract stylization is used to facilitate guidance of a viewer's gaze to prioritized information. However, to adapt visualization to different contexts and contents and to support saliency-guided visualization based on user interaction or dynamically changing thematic information, a combination of different graphic styles is necessary. Design and implementation of such combined graphic styles pose a number of challenges, specifically from the perspective of real-time 3D visualization. In this paper, the authors present a concept and an implementation of a system that enables different presentation styles, their seamless integration within a single view, and parametrized transitions between them, which are defined according to tasks, camera view, and image resolution. The paper outlines potential usage scenarios and application fields together with a performance evaluation of the implementation.

关键词： I.3.3 [Computer Graphics]: Picture/Image Generation&mdash viewing algorithms I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism&mdash

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Out-of-core selection and editing of huge point clouds

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COMPUTERS & GRAPHICS-UK 2011年第2期35卷 342-351页

作者： Scheiblauer, Claus Wimmer, Michael Inst Comp Graph & Algorithms A-1040 Vienna Austria

In this paper we present an out-of-core editing system for point clouds, which allows selecting and modifying arbitrary parts of a huge point cloud interactively. We can use the selections to segment the point cloud, to delete points, or to render a preview of the model without the points in the selections. Furthermore, we allow for inserting points into an already existing point cloud. All operations are conducted on a rendering optimized data structure that uses the raw point cloud from a laser scanner, and no additionally created points are needed for an efficient level-of-detail (LOD) representation using this data structure. We also propose an algorithm to alleviate the artifacts when rendering a point cloud with large discrepancies in density in different areas by estimating point sizes heuristically. These estimated point sizes can be used to mimic a closed surface on the raw point cloud, also when the point cloud is composed of several raw laser scans. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Point-based rendering viewing algorithms Graphics data structures and data types

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Visibility Equalizer Cutaway Visualization of Mesoscopic Biological Models

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COMPUTER GRAPHICS FORUM 2016年第3期35卷 161-170页

作者： Le Muzic, M. Mindek, P. Sorger, J. Autin, L. Goodsell, D. S. Viola, I. TU Wien Vienna Austria VRVis Res Ctr Vienna Austria Scripps Res Inst La Jolla CA 92037 USA

In scientific illustrations and visualization, cutaway views are often employed as an effective technique for occlusion management in densely packed scenes. We propose a novel method for authoring cutaway illustrations of mesoscopic biological models. In contrast to the existing cutaway algorithms, we take advantage of the specific nature of the biological models. These models consist of thousands of instances with a comparably smaller number of different types. Our method constitutes a two stage process. In the first step, clipping objects are placed in the scene, creating a cutaway visualization of the model. During this process, a hierarchical list of stacked bars inform the user about the instance visibility distribution of each individual molecular type in the scene. In the second step, the visibility of each molecular type is fine-tuned through these bars, which at this point act as interactive visibility equalizers. An evaluation of our technique with domain experts confirmed that our equalizer-based approach for visibility specification is valuable and effective for both, scientific and educational purposes.

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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OMiCroN - Oblique Multipass Hierarchy Creation while Navigating

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COMPUTERS & GRAPHICS-UK 2019年 84卷 42-54页

作者： da Silva, Vinicius Esperanca, Claudio Marroquim, Ricardo Inst Pure & Appl Math IMPA VISGRAF Lab Estr Dona Castorina 110 BR-22460320 Rio De Janeiro RJ Brazil Fed Univ Rio De Janeiro UFRJ Ctr Tecnol Comp Graph Lab LCG Block H BR-21941972 Rio De Janeiro RJ Brazil Delft Univ Technol TU Delft Comp Graph & Visualizat Grp Mourik Broekmanweg 6 Delft Netherlands

Rendering large point clouds ordinarily requires building a hierarchical data structure for accessing the points that best represent the object for a given viewing frustum and level-of-detail. The building of such data structures frequently represents a large portion of the cost of the rendering pipeline both in terms of time and space complexity, especially when rendering is done for inspection purposes only. This problem has been addressed in the past by incremental construction approaches, but these either result in low quality hierarchies or in longer construction times. In this work we present OMiCroN - Oblique Multipass Hierarchy Creation while Navigating - which is the first algorithm capable of immediately displaying partial renders of the geometry, provided the cloud is made available sorted in Morton order. OMiCroN is fast, being capable of building the entire data structure in memory spending an amount of time that is comparable to that of just reading the cloud from disk. Thus, there is no need for storing an expensive hierarchy, nor for delaying the rendering until the whole hierarchy is read from disk. In fact, a pipeline coupling OMiCroN with an incremental sorting algorithm running in parallel can start rendering as soon as the first sorted prefix is produced, making this setup very convenient for streamed viewing. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Graphics data structures Object hierarchies viewing algorithms Computational Geometry Computer Graphics

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Perceptually-motivated Stereoscopic Film Grain

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COMPUTER GRAPHICS FORUM 2014年第7期33卷 349-358页

作者： Templin, Krzysztof Didyk, Piotr Myszkowski, Karol Seidel, Hans-Peter MPI Informat Saarbrucken Germany MIT CSAIL Cambridge MA USA

Independent management of film grain in each view of a stereoscopic video can lead to visual discomfort. The existing alternative is to project the grain onto the scene geometry. Such grain, however, looks unnatural, changes object perception, and emphasizes inaccuracies in depth arising during 2D-to-3D conversion. We propose an advanced method of grain positioning that scatters the grain in the scene space. In a series of perceptual experiments, we estimate the optimal parameter values for the proposed method, analyze the user preference distribution among the proposed and the two existing methods, and show influence of the method on the object perception.

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

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ConnectedCharts: Explicit Visualization of Relationships between Data Graphics

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COMPUTER GRAPHICS FORUM 2012年第3期31卷 1285-1294页

作者： Viau, C. McGuffin, M. J. Ecole Technol Super Toronto ON Canada

Multidimensional multivariate data can be visualized using many different well-known charts, such as bar charts, stacked bar charts, grouped bar charts, scatterplots, or pivot tables, or also using more advanced high-dimensional techniques such as scatterplot matrices (SPLOMs) or parallel coordinate plots (PCPs). These many techniques have different advantages, and users may wish to use several charts or data graphics to understand a dataset from different perspectives. We present ConnectedCharts, a technique for displaying relationships between multiple charts. ConnectedCharts allow for hybrid combinations of bar charts, scatterplots, and parallel coordinates, with curves drawn to show the conceptual links between charts. The charts can be thought of as coordinated views, where linking is achieved not only through interactive brushing, but also with explicitly drawn curves that connect corresponding data tuples or axes. We present a formal description of a design space of many simple charts, and also identify different kinds of connections that can be displayed between related charts. Our prototype implementation demonstrates how the connections between multiple charts can make relationships clearer and can serve to document the history of a user's analytical process, leading to potential applications in visual analytics and dashboard design.

关键词： I.3.3 [Computer Graphics]: Picture/Image Generation viewing algorithms

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Advanced techniques for high-quality multi-resolution volume rendering

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COMPUTERS & GRAPHICS-UK 2004年第1期28卷 51-58页

作者： Guthe, S Strasser, W Univ Tubingen GRIS WSI D-72076 Tubingen Germany

We present several improvements for compression-based multi-resolution rendering of very large volume data sets at interactive to real-time frame rates on standard PC hardware. The algorithm accepts scalar or multi-variant data sampled on a regular grid as input. The input data are converted into a compressed hierarchical wavelet representation in a pre-processing step. During rendering, the wavelet representation is decompressed on-the-fly and rendered using hardware texture mapping. The level-of-detail used for rendering is adapted to the estimated screen-space error. To.-increase the rendering performance additional visibility tests, such as empty space skipping and occlusion culling, are applied. Furthermore, we discuss how to render the remaining multi-resolution blocks efficiently using modern graphics hardware. Using a prototype implementation of this algorithm we are able to perform a high-quality interactive rendering of large data sets on a single off-the-shelf PC. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： viewing algorithms data compaction and compression

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Re-Compositable Panoramic Selfie with Robust Multi-Frame Segmentation and Stitching

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COMPUTER GRAPHICS FORUM 2016年第7期35卷 227-236页

作者： Li, Kai Wang, Jue Liu, Yebin Xu, Li Dai, Qionghai Shanghai Univ Sch Commun & Informat Engn Shanghai 200041 Peoples R China Tsinghua Univ Dept Automat Beijing Peoples R China Adobe Res Basel Switzerland SenseTime Grp Ltd Hong Kong Hong Kong Peoples R China

It is a challenging task for ordinary users to capture selfies with a good scene composition, given the limited freedom to position the camera. Creative hardware (e.g., selfie sticks) and software (e.g., panoramic selfie apps) solutions have been proposed to extend the background coverage of a selife, but to achieve a perfect composition on the spot when the selfie is captured remains to be difficult. In this paper, we propose a system that allows the user to shoot a selfie video by rotating the body first, then produce a final panoramic selfie image with user-guided scene composition as postprocessing. Our key technical contribution is a fully automatic, robust multi-frame segmentation and stitching framework that is tailored towards the special characteristics of selfie images. We analyze the sparse feature points and employ a spatial-temporal optimization for bilayer feature segmentation, which leads to more reliable background alignment than previous image stitching techniques. The sparse classification is then propagated to all pixels to create dense foreground masks for person-background composition. Finally, based on a user-selected foreground position, our system uses content-preserving warping to produce a panoramic seflie with minimal distortion to the face region. Experimental results show that our approach can reliably generate high quality panoramic selfies, while a simple combination of previous image stitching and segmentation approaches often fails.

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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Visualizing the Positional and Geometrical Variability of Isosurfaces in Uncertain Scalar Fields

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COMPUTER GRAPHICS FORUM 2011年第3期30卷 951-960页

作者： Pfaffelmoser, Tobias Reitinger, Matthias Westermann, Ruediger Tech Univ Munich Comp Graph & Visualizat Grp D-8000 Munich Germany

We present a novel approach for visualizing the positional and geometrical variability of isosurfaces in uncertain 3D scalar fields. Our approach extends recent work by Pothkow and Hege [PH10] in that it accounts for correlations in the data to determine more reliable isosurface crossing probabilities. We introduce an incremental update-scheme that allows integrating the probability computation into front-to-back volume ray-casting efficiently. Our method accounts for homogeneous and anisotropic correlations, and it determines for each sampling interval along a ray the probability of crossing an isosurface for the first time. To visualize the positional and geometrical uncertainty even under viewing directions parallel to the surface normal, we propose a new color mapping scheme based on the approximate spatial deviation of possible surface points from the mean surface. The additional use of saturation enables to distinguish between areas of high and low statistical dependence. Experimental results confirm the effectiveness of our approach for the visualization of uncertainty related to position and shape of convex and concave isosurface structures.

关键词： I.3.3 [Computer Graphics]: Picture/Image Generation Display algorithms viewing algorithms

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