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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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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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GPU-Based Ray-Casting of Spherical Functions Applied to High Angular Resolution Diffusion Imaging

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2011年第5期17卷 612-625页

作者： van Almsick, Markus Peeters, Tim H. J. M. Prckovska, Vesna Vilanova, Anna Romeny, Bart ter Haar Eindhoven Univ Technol Dept Biomed Engn NL-5600 MB Eindhoven Netherlands

Any sufficiently smooth, positive, real-valued function psi : S-2 -> IR+ on a sphere S-2 can be expanded by a Laplace expansion into a sum of spherical harmonics. Given the Laplace expansion coefficients, we provide a CPU and GPU-based algorithm that renders the radial graph of psi in a fast and efficient way by ray-casting the glyph of psi in the fragment shader of a GPU. The proposed rendering algorithm has proven highly useful in the visualization of high angular resolution diffusion imaging (HARDI) data. Our implementation of the rendering algorithm can display simultaneously thousands of glyphs depicting the local diffusivity of water. The rendering is fast enough to allow for interactive manipulation of large HARDI data sets.

关键词： Computer graphics viewing algorithms three-dimensional graphics and realism computer applications life and medical sciences

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

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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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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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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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ADR - Anatomy-Driven Reformation

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2014年第12期20卷 2496-2505页

作者： Kretschmer, Jan Soza, Grzegorz Tietjen, Christian Suehling, Michael Preim, Bernhard Stamminger, Marc FAU Erlangen Dept Comp Graph Forchheim Germany Siemens Healthcare Comp Tomog Forchheim Germany Univ Magdeburg Dept Simulat & Graph D-39106 Magdeburg Germany

Dedicated visualization methods are among the most important tools of modern computer-aided medical applications. Reformation methods such as Multiplanar Reformation or Curved Planar Reformation have evolved as useful tools that facilitate diagnostic and therapeutic work. In this paper, we present a novel approach that can be seen as a generalization of Multiplanar Reformation to curved surfaces. The main concept is to generate reformatted medical volumes driven by the individual anatomical geometry of a specific patient. This process generates flat views of anatomical structures that facilitate many tasks such as diagnosis, navigation and annotation. Our reformation framework is based on a non-linear as-rigid-as-possible volumetric deformation scheme that uses generic triangular surface meshes as input. To manage inevitable distortions during reformation, we introduce importance maps which allow controlling the error distribution and improving the overall visual quality in areas of elevated interest. Our method seamlessly integrates with well-established concepts such as the slice-based inspection of medical datasets and we believe it can improve the overall efficiency of many medical workflows. To demonstrate this, we additionally present an integrated visualization system and discuss several use cases that substantiate its benefits.

关键词： Medical Visualization Volume Reformation viewing algorithms

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