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QuadStack: An Efficient Representation and Direct Rendering of Layered datasets

IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER graphics 2021年第9期27卷 3733-3744页

作者： Graciano, Alejandro Rueda, Antonio J. Pospisil, Adam Bittner, Jiri Benes, Bedrich Univ Jaen Jaen 23071 Spain Univ Jaen Escuela Politecn Super Comp Sci Jaen 23071 Spain Czech Tech Univ Prague 16636 6 Czech Republic Purdue Univ Technol W Lafayette IN 47907 USA Purdue Univ Comp Sci W Lafayette IN 47907 USA

We introduce QuadStack, a novel algorithm for volumetric data compression and direct rendering. Our algorithm exploits the data redundancy often found in layered datasets which are common in science and engineering fields such as geology, biology, mechanical engineering, medicine, etc. QuadStack first compresses the volumetric data into vertical stacks which are then compressed into a quadtree that identifies and represents the layered structures at the internal nodes. The associated data (color, material, density, etc.) and shape of these layer structures are decoupled and encoded independently, leading to high compression rates (4x to 54x of the original voxel model memory footprint in our experiments). We also introduce an algorithm for value retrieving from the QuadStack representation and we show that the access has logarithmic complexity. Because of the fast access, QuadStack is suitable for efficient data representation and direct rendering. We show that our GPU implementation performs comparably in speed with the state-of-the-art algorithms (18-79 MRays/s in our implementation), while maintaining a significantly smaller memory footprint.

关键词： Rendering (computer graphics) data visualization graphics processing units data models Geology data structures Ray tracing Computer graphics object hierarchies graphics data structures and data types

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Optimal Path Maps on the GPU

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER graphics 2020年第9期26卷 2863-2874页

作者： Farias, Renato Kallmann, Marcelo Univ Calif Comp Sci & Engn Dept Merced CA 95343 USA

We introduce a new method for computing optimal path maps on the GPU using OpenGL shaders. Our method explores GPU rasterization as a way to propagate optimal costs on a polygonal 2D environment, producing optimal path maps which can efficiently be queried at run-time. Our method is implemented entirely with GPU shaders, does not require pre-computation, addresses optimal path maps with multiple points and line segments as sources, and introduces a new optimal path map concept not addressed before: maps with weights at vertices representing possible changes in traversal speed. The produced maps offer new capabilities not explored by previous navigation representations and at the same time address paths with global optimality, a characteristic which has been mostly neglected in animated virtual environments. The proposed path maps partition the input environment into the regions sharing a same parent point along the shortest path to the closest source, taking into account possible speed changes at vertices. The proposed approach is particularly suitable for the animation of multiple agents moving toward the entrances or exits of a virtual environment, a situation which is efficiently represented with the proposed path maps.

关键词： graphics processing units Path planning Microsoft Windows Geometry Navigation Virtual environments Computational efficiency graphics data structures and data types path planning shortest path maps navigation GPU programming

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Know Your Enemy: Identifying Quality Problems of Time Series data 11

Know Your Enemy: Identifying Quality Problems of Time Series...

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IEEE Pacific Visualization Symposium (IEEE PacificVis)

作者： Gschwandtner, Theresia Erhart, Oliver TU Wien Inst Visual Comp & Human Ctr Technol Vienna Austria

ISBN: (纸本)9781538614242

Sensible data analysis requires data quality control. An essential part of this is data profiling, which is the identification and assessment of data quality problems as a prerequisite for adequately handling these problems. Differentiating between actual quality problems and unusual, but valid data values requires the "human-in-the-loop" through the use of visual analytics. Unfortunately, existing approaches for data profiling do not adequately support the special characteristics of time, which is imperative to identify quality problems in time series data - a data type prevalent in a multitude of disciplines. In this design study paper, we outline the design, implementation, and evaluation of "Know Your Enemy" (KYE) - a visual analytics approach to assess the quality of time series data. KYE supports the task of data profiling with (1) predefined data quality checks, (2) user-definable, customized quality checks, (3) interactive visualization to explore and reason about automatically detected problems, and (4) the visual identification of hidden quality problems.

关键词： H.5.2[Information Interfaces And Presentation]:User Interfaces User-centered design I.3.6[Computer graphics]: Methodology and Techniques graphics data structures and data types

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Decoupled Space and Time Sampling of Motion and Defocus Blur for Unified Rendering of Transparent and Opaque Objects

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COMPUTER graphics FORUM 2016年第7期35卷 441-450页

作者： Widmer, S. Wodniok, D. Thul, D. Guthe, S. Goesele, M. Tech Univ Darmstadt Grad Sch Computat Engn Darmstadt Germany Tech Univ Darmstadt Darmstadt Germany

We propose a unified rendering approach that jointly handles motion and defocus blur for transparent and opaque objects at interactive frame rates. Our key idea is to create a sampled representation of all parts of the scene geometry that are potentially visible at any point in time for the duration of a frame in an initial rasterization step. We store the resulting temporally-varying fragments (t-fragments) in a bounding volume hierarchy which is rebuild every frame using a fast spatial median construction algorithm. This makes our approach suitable for interactive applications with dynamic scenes and animations. Next, we perform spatial sampling to determine all t-fragments that intersect with a specific viewing ray at any point in time. Viewing rays are sampled according to the lens uv-sampling for depth-of-field effects. In a final temporal sampling step, we evaluate the predetermined viewing ray/t-fragment intersections for one or multiple points in time. This allows us to incorporate all standard shading effects including transparency. We describe the overall framework, present our GPU implementation, and evaluate our rendering approach with respect to scalability, quality, and performance.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.6 [Computer graphics]: Methodology and Techniques&mdash graphics data structures and data types I.3.7 [Computer graphics]: Three-Dimensional graphics and Realism&mdash Raytracing

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Quality Metric for Spherical Panoramic Video 10

Quality Metric for Spherical Panoramic Video

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10th Conference on Optics and Photonics for Information Processing

作者： Zakharchenko, Vladyslav Choi, Kwang Pyo Park, Jeong Hoon Samsung Elect Co Ltd R&D Ctr Seoul South Korea

ISBN: (数字)9781510603325

ISBN: (纸本)9781510603318;9781510603325

Virtual reality (VR)/ augmented reality (AR) applications allow users to view artificial content of a surrounding space simulating presence effect with a help of special applications or devices. Synthetic contents production is well known process form computer graphics domain and pipeline has been already fixed in the industry. However emerging multimedia formats for immersive entertainment applications such as free-viewpoint television (FTV) or spherical panoramic video require different approaches in content management and quality assessment. The international standardization on FTV has been promoted by MPEG. This paper is dedicated to discussion of immersive media distribution format and quality estimation process. Accuracy and reliability of the proposed objective quality estimation method had been verified with spherical panoramic images demonstrating good correlation results with subjective quality estimation held by a group of experts.

关键词： Video quality projection systems free-viewpoint television graphics data structures and data types spherical panoramic video immersive media

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Networks of Names: Visual Exploration and Semi-Automatic Tagging of Social Networks from Newspaper Articles

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COMPUTER graphics FORUM 2014年第3期33卷 211-220页

作者： Kochtchi, A. von Landesberger, T. Biemann, C. Tech Univ Darmstadt Language Technol Grp Darmstadt Germany Tech Univ Darmstadt Interact Graph Syst Grp Darmstadt Germany

Understanding relationships between people and organizations by reading newspaper articles is difficult to manage for humans due to the large amount of data. To address this problem, we present and evaluate a new visual analytics system, which offers interactive exploration and tagging of social networks extracted from newspapers. For the visual exploration of the network, we extract "interesting" neighbourhoods of nodes, using a new degree of interest (DOI) measure based on edges instead of nodes. It improves the seminal definition of DOI, which we find to produce the same "globally interesting" neighbourhoods in our use case, regardless of the query. Our approach allows answering different user queries appropriately, avoiding uniform search results. We propose a user-driven pattern-based classifier for discovery and tagging of non-taxonomic semantic relations. Our approach does not require any a-priori user knowledge, such as expertise in syntax or pattern creation. An evaluation shows that our classifier is capable of identifying known lexico-syntactic patterns as well as various domain-specific patters. Our classifier yields good results already with a small amount of training, and continuously improves through user feedback. We conduct a user study to evaluate whether our visual interactive system has an impact on how users tag relationships, as compared to traditional text-based interfaces. Study results suggest that users of the visual system tend to tag more concisely, avoiding too abstract or overly specific relationship labels.

关键词： Categories and Subject Descriptors (according to ACM CCS) H.5.2 [Information Interfaces and Presentation]: User Interfaces (D.2.2 H.1.2 I.3.6)&mdash Interaction styles (e. g. commands menus forms direct manipulation) I.3.6 [Computer graphics]: Methodology and Techniques&mdash graphics data structures and data types

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A Quantized Boundary Representation of 2D Flows

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COMPUTER graphics FORUM 2012年第3期31卷 945-954页

作者： Levine, J. A. Jadhav, S. Bhatia, H. Pascucci, V. Bremer, P. -T. Univ Utah Sci Comp & Imaging Inst Salt Lake City UT 84112 USA Lawrence Livermore Natl Lab Livermore CA USA

Analysis and visualization of complex vector fields remain major challenges when studying large scale simulation of physical phenomena. The primary reason is the gap between the concepts of smooth vector field theory and their computational realization. In practice, researchers must choose between either numerical techniques, with limited or no guarantees on how they preserve fundamental invariants, or discrete techniques which limit the precision at which the vector field can be represented. We propose a new representation of vector fields that combines the advantages of both approaches. In particular, we represent a subset of possible streamlines by storing their paths as they traverse the edges of a triangulation. Using only a finite set of streamlines creates a fully discrete version of a vector field that nevertheless approximates the smooth flow up to a user controlled error bound. The discrete nature of our representation enables us to directly compute and classify analogues of critical points, closed orbits, and other common topological structures. Further, by varying the number of divisions (quantizations) used per edge, we vary the resolution used to represent the field, allowing for controlled precision. This representation is compact in memory and supports standard vector field operations.

关键词： I.3.6 [Computer graphics]: Methodology and Techniques&mdash graphics data structures and data types G.1.2 [Numerical Analysis]: Approximation&mdash Approximation of surfaces and contours

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Rasterized Bounding Volume Hierarchies

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COMPUTER graphics FORUM 2012年第2期31卷 403-412页

作者： Novak, Jan Dachsbacher, Carsten Karlsruhe Inst Technol Comp Graph Grp Karlsruhe Germany

We present the rasterized bounding volume hierarchy (RBVH), a compact data structure that accelerates approximate ray casting of complex meshes and provides adjustable level of detail. During construction, we identify subtrees of BVHs containing surfaces that can be represented by height fields. For these subtrees the conventional ray-surface intersection, which possibly involves a large number of triangles, is replaced by a simple ray marching procedure to find the intersection with the surface. We describe GPU algorithms for construction, ray casting, and data querying of the RBVH that achieve comparable or higher performance than state of the art acceleration structures for triangle meshes. Moreover, RBVHs provide an inherent surface parameterization for storing data on the surfaces and natively handle triangle and point-based surface representations. We also show that RBVHs support adaptive level-of-detail and can be combined with traditional BVHs to handle complex scenes.

关键词： I.3.6 [Computer graphics]: Methodology and Techniques&mdash graphics data structures and data types

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Domino Tiling:A New Method of Real-Time Conforming Mesh Construction for Rendering Changeable Height Fields

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Journal of Computer Science & Technology 2011年第6期26卷 971-987页

作者： Dorde M. Durdevi Igor I. Tartalja School of Electrical Engineering University of Belgrade

In this paper we present a novel GPU-oriented method of creating an inherently continuous triangular mesh for tile-based rendering of regular height fields. The method is based on tiling data-independent semi-regular meshes of non-uniform structure, a technique that is quite different from other mesh tiling approaches. A complete, memory efficient set of mesh patterns is created by an off-line procedure and stored into the graphics adapter＇s memory at runtime. At rendering time, for each tile, one of the precomputed mesh patterns is selected for rendering. The selected mesh pattern fits the required level of details of the tile and ensures seamless connection with other adjacent mesh patterns, like in a game of dominoes. The scalability potential of the proposed method is demonstrated through quadtree hierarchical grouping of tiles. The efficiency is verified by experimental results on height fields for terrain representation, where the method achieves high frame rates and sustained triangle throughput on high resolution viewports with sub-pixel error tolerance. Frame rate sensitivity to real-time modifications of the height field is measured, and it is shown that the method is very tolerant and consequently well tailored for applications dealing with rapidly changeable phenomena represented by height fields.

关键词： graphics data structures and data types height field surface representation level of details real-time heightfield manipulation view-dependent rendering

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PaperVis: Literature Review Made Easy

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COMPUTER graphics FORUM 2011年第3期30卷 721-730页

作者： Chou, J. -K. Yang, C. -K. Natl Taiwan Univ Sci & Technol Dept Informat Management Taipei Taiwan

Reviewing literatures for a certain research field is always important for academics. One could use Google-like information seeking tools, but oftentimes he/she would end up obtaining too many possibly related papers, as well as the papers in the associated citation network. During such a process, a user may easily get lost after following a few links for searching or cross-referencing. It is also difficult for the user to identify relevant/important papers from the resulting huge collection of papers. Our work, called PaperVis, endeavors to provide a user-friendly interface to help users quickly grasp the intrinsic complex citation-reference structures among a specific group of papers. We modify the existing Radial Space Filling (RSF) and Bullseye View techniques to arrange involved papers as a node-link graph that better depicts the relationships among them while saving the screen space at the same time. PaperVis applies visual cues to present node attributes and their transitions among interactions, and it categorizes papers into semantically meaningful hierarchies to facilitate ensuing literature exploration. We conduct experiments on the InfoVis 2004 Contest dataset to demonstrate the effectiveness of PaperVis.

关键词： I.3.3 [Computer graphics]: Picture/Image Generation Line and curve generation I.3.6 [Computer graphics]: Methodology and Techniques graphics data structures and data types

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