http://www.rssboard.org/rss-specification 720 https://escholarship.org/uc/ucdavis_idav_pubs/rss Recent eScholarship items from IDAV Publications Fri, 15 May 2026 09:06:27 +0000 https://escholarship.org/uc/item/5nm063xk Accurate computation of depth-of-field effects in computer graphics rendering is generally very time consuming, creating a problematic workflow for film authoring. The computation is particularly challenging because it depends on large-scale spatially-varying filtering that must accurately respect complex boundaries. A variety of real-time algorithms have been proposed for games, but the compromises required to achieve the necessary frame rates have made them them unsuitable for film. Here we introduce an approximatedepth-of-field computation that is good enough for film preview, yet can be computed interactively on a GPU. The computation creates depth-of-field blurs by simulating the heat equation for a nonuniform medium. Our alternating direction implicit solution gives rise to separable spatially varying recursive filters that can compute large-kernel convolutions in constant time per pixel while respecting the boundaries between in-focus and out-of-focus objects. Recursive... https://escholarship.org/uc/item/5nm063xk Fri, 28 Feb 2020 00:00:00 +0000 Kass, Michael Lefohn, Aaron Owens, John D. https://escholarship.org/uc/item/9xk5f6mj Given a sample of points from the boundary of an object IR3, we construct a representation of the object as a union of balls. We use many fewer balls than previous constructions, but our shape representation is better. We bound the distance from the surface of the union to the original object surface, and show that when the sampling is sufficiently dense the two are homeomorphic. This implies a topolgical relationship between the true medial axis of the object and both the medial axis, and the α-shape, of the union of balls. We show that the set of ball centers in our construction converges to the true medial axis as the sampling density increases. https://escholarship.org/uc/item/9xk5f6mj Fri, 28 Jun 2019 00:00:00 +0000 Amenta, Nina Kolluri, Ravi Krishna https://escholarship.org/uc/item/9xg157qp Animation data, from motion capture or other sources, is becoming increasingly available and provides high quality motion, but is difficult to customize for the needs of a particular application. This is especially true when stylistic changes are needed, for example, to reflect a character's changing mood, differentiate one character from another or meet the precise desires of an animator. We introduce a system for editing animation data that is particularly well suited to making stylistic changes. Our approach transforms the joint angle representation of animation data into a set of pose parameters more suitable for editing. These motion drives include position data for the wrists, ankles and center of mass, as well as the rotation of the pelvis. We also extract correlations between drives and body movement, specifically between wrist position and the torso angles. The system solves for the pose at each frame based on the current values of these drives and correlations using... https://escholarship.org/uc/item/9xg157qp Fri, 28 Jun 2019 00:00:00 +0000 Neff, Michael Kim, Yejin https://escholarship.org/uc/item/9x97g9fp Our capability to generate increasingly large and more complex datasets has established the need for scalable methods that can provide insight into important variable trends. Query-driven methods are among the small subset of techniques that are able to address both large and highly complex data sets. This paper presents a new method in which coherent and meaningful visualizations are constructed to convey relational information about the trends that exist \emph{between} variables in a query. Correlation fields are created between pairs of variables and used in conjunction with the cumulative distribution function of each of the query's variables to reveal, both visually and statistically, trends in variable behavior and interactions. We illustrate our concepts by discussing interactions between variables in two flame-front simulations. https://escholarship.org/uc/item/9x97g9fp Fri, 28 Jun 2019 00:00:00 +0000 Gosink, Luke Anderson, John C. Bethel, Wes Joy, Ken https://escholarship.org/uc/item/9x4542q1 Given a surface triangulation in three-dimensional space, an algorithm is developed to iteratively remove triangles from the triangulation. An underlying parametric or implicit surface representation is not required. An order is introduced on the set of triangles by considering curvature at their vertices. Triangles in nearly planar surface regions are prime candidates for removal. The degree of reduction can be specified by a percentage or, in the case of biviariate functions, by an error tolerance. https://escholarship.org/uc/item/9x4542q1 Fri, 28 Jun 2019 00:00:00 +0000 Hamann, Bernd https://escholarship.org/uc/item/9wt4b34b Acoustic quality in room acoustics is measured by well defined quantities, like definition, which can be derived from simulated impulse response filters or measured values. These take into account the intensity and phase shift of multiple reflections due to a wave front emanating from a sound source. Definition (D50) and clarity (C50) for example correspond to the fraction of the energy received in total to the energy received in the first 50 ms at a certain listener position. Unfortunately, the impulse response measured at a single point does not provide any information about the direction of reflections, and about the reflection surfaces which contribute to this measure. For the visualization of room acoustics, however, this information is very useful since it allows to discover regions with high contribution and provides insight into the influence of all reflecting surfaces to the quality measure. We use the phonon tracing method to calculate the contribution of the reflection... https://escholarship.org/uc/item/9wt4b34b Fri, 28 Jun 2019 00:00:00 +0000 Michel, Frank Deines, Eduard Bertram, Martin Garth, Christoph Hagen, Hans https://escholarship.org/uc/item/9v9799q1 The simulation of complex events is a challenging task and often requires careful selection of simulation parameters. With the availability of vast computation resources, it has become possible to run several alternative parameter settings or simulation models in parallel, creating an 'ensemble' of possible outcomes for a given event of interest. Recently, the visual analysis of such ensemble data has repeatedly come up as one of the most important new areas of visualization and it is expected to have a wide impact on the field of visualization in the next few years. The main challenge is to develop expressive visualizations of properties of this set of solutions, the ensemble, to support scientists in this challenging parameter-space exploration task. This paper presents and explores future challenges for ensemble visualization. https://escholarship.org/uc/item/9v9799q1 Fri, 28 Jun 2019 00:00:00 +0000 Obermaier, Harald Joy, Kenneth I. https://escholarship.org/uc/item/9tc0k5jn Multiresolution representations of high-dimensional scattered data is an outstanding problem in the field of scientific visualization. This paper introduces a data hierarchy of Voronoi diagrams as a versatile solution. We implemented two programs to demonstrate this, the first of which uses a constant function to approximate the data within each Voronoi tile and the second program uses the Sibson interpolant within each tile [5]. https://escholarship.org/uc/item/9tc0k5jn Fri, 28 Jun 2019 00:00:00 +0000 Schussman, Shirley Bertram, Martin Hamann, Bernd Joy, Ken https://escholarship.org/uc/item/9sj8c9xb The analysis and modeling of the response of parts of the body provides valuable insight into many features of the head-related transfer function (HRTF). In spatial sound simulations, partial models, such as the spherical head model, can also generate simple and effective approximate localization cues. In this paper, we consider the composition of an approximate HRTF from the responses of structural components by making use of detailed measurements of isolated pinnae and of a pinna-less head and torso. We determine that such a composition is sensitive to additional geometric parameters that can be obtained from anthropometry. We show that, with such parameters, simple composition rules can produce a good correspondence between measured and composite HRTFs. https://escholarship.org/uc/item/9sj8c9xb Fri, 28 Jun 2019 00:00:00 +0000 Algazi, Ralph Duda, Richard O Morrison, Reed P. Thompson, Dennis M. https://escholarship.org/uc/item/9sg0450m We present a new method for simplifying large data sets that contain material interfaces. Material interfaces embedded in the meshes of computational data sets are often a source of error for simplification algorithms because they represent discontinuities in the scalar interfaces explicitly in a data simplification process, allows us to use separate field representations for each material over a single cell. https://escholarship.org/uc/item/9sg0450m Fri, 28 Jun 2019 00:00:00 +0000 Gregorski, Benjamin F. Hamann, Bernd Joy, Ken https://escholarship.org/uc/item/9s4769qq We demonstrate the use of a combination of perceptually effective techniques for visualizing magnetic field data from the DIII-D Tokamak. These techniques can be implemented to run very efficiently on machines with hardware support for OpenGL. Interactive speeds facilitate clear communication of magnetic field structure, enhancing fusion scientists' understanding of their data, and thereby accelerating their research. https://escholarship.org/uc/item/9s4769qq Fri, 28 Jun 2019 00:00:00 +0000 Schussman, Greg Ma, Kwan-Liu Schissel, David Evans, Todd https://escholarship.org/uc/item/9rr1f5mw The topology of vector fields offers a well known way to show a ''condensed'' view of the stream line behavior or a vector field. The global structure of a field can be shown without time-consuming user interaction. With regard to large data visualization, one encounters a major drawback: the necessity to analyze a whole data set, even when interested in only a small region. We show that one can localize the topology concept by including the boundary in the topology analysis. The idea is demonstrated for a turbulent swirling jet simulation example. Our concept works for all planar, piecewise analytic vector fields on bounded domains. https://escholarship.org/uc/item/9rr1f5mw Fri, 28 Jun 2019 00:00:00 +0000 Scheuermann, Gerik Hamann, Bernd Joy, Ken Kollmann, Wolfgang https://escholarship.org/uc/item/9r15d4zk We explore software mechanisms for managing irregular tasks on graphics processing units (GPUs). We demonstrate that dynamic scheduling and efficient memory management are critical problems in achieving high efficiency on irregular workloads. We experiment with several task-management techniques, ranging from the use of a single monolithic task queue to distributed queuing with task stealing and donation. On irregular workloads, we show that both centralized and distributed queues have more than 100 times as much idle times as our task-stealing and -donation queues. Our preferred choice is task-donation because of comparable performance to task-stealing while using less memory overhead. To help in this analysis, we use an artificial task-management system that monitors performance and memory usage to quantify the impact of these different techniques. We validate our results by implementing a Reyes renderer with its irregular split-and-dice workload that is able to achieve real-time... https://escholarship.org/uc/item/9r15d4zk Fri, 28 Jun 2019 00:00:00 +0000 Tzeng, Stanley Patney, Anjul Owens, John D. https://escholarship.org/uc/item/9qz894md We show how the contralateral head-related transfer function (HRTF) can be modeled by a simple transformation of the ipsilateral HRTF. Components of the transformation are based on a spherical model of the listener's head. Listening tests reveal that the average localization error introduced by the model is approximately 5 degree. https://escholarship.org/uc/item/9qz894md Fri, 28 Jun 2019 00:00:00 +0000 Avendano, Carlos Duda, Richard O Algazi, Ralph https://escholarship.org/uc/item/9qq2h12n A major implementation of visualization algorithms on very-large unstructured scientific data sets is the suitable internal representation of the data. Not only must we represent the data elements themselves, but we must also represent the connectivity or topological relationships between the data. We present three data structures for unstructured meshes that are designed to fully represent the topological connectivity in the mesh, but also minimize the data storage requirements in representing the mesh. The key idea is to represent the topology of the mesh by the use of a single data item-the lath-which can be used to encapsulate the topological within the mesh. We present and analyze algorithms that query the spatial relations and properties of these data structures, and analyze the data structures of the dual mesh induced by each. https://escholarship.org/uc/item/9qq2h12n Fri, 28 Jun 2019 00:00:00 +0000 Joy, Ken Legakis, Justin MacCracken, Ron https://escholarship.org/uc/item/9qh612tk We present a new algorithm for material boundary interface reconstruction from data sets containing volume fractions. We transform the reconstruction problem to a problem that analyzes the dual data set, where each vertex in the dual mesh has an associated barycentric coordinate tuple that represents the fraction of each material present. After constructing the dual tetrahedral mesh from the original mesh, we construct material boundaries by mapping a tetrahedron into barycentric space and calculating the intersections with Voronoi cells in barycentric space. These intersections are mapped back to the original physical space and triangulated to form the boundary surface approximation. This algorithm can be applied to any grid structure and can treat any number of materials per element/vertex https://escholarship.org/uc/item/9qh612tk Fri, 28 Jun 2019 00:00:00 +0000 Bonnell, Kathleen S. Schikore, Daniel A. Duchaineau, Mark A. Hamann, Bernd Joy, Ken https://escholarship.org/uc/item/9qd879w9 A Foveal Inset for Large Display Environments https://escholarship.org/uc/item/9qd879w9 Fri, 28 Jun 2019 00:00:00 +0000 Ahlborn, Benjamin A. Kreylos, Oliver Hamann, Bernd Staadt, Oliver G. https://escholarship.org/uc/item/9pg389hg Mahalanobis-type distances in which the shape matrix is derived from a consistent highbreakdown robust multivariate location and scale estimator can be used to find outlying points. Hardin and Rocke (http://www.cipic.ucdavis.edu/,,,dmrocke/preprints.htrnl)developed a new method for identifying outliers in a one-cluster setting using an F distribution. We extend the method to the multiple cluster case which gives a robust clustering method in conjunction with an outlier identification method. We provide results of the F distribution method for multiple clusters which have different sizes and shapes. https://escholarship.org/uc/item/9pg389hg Fri, 28 Jun 2019 00:00:00 +0000 Hardin, Johanna Rocke, David https://escholarship.org/uc/item/9ns2d70c The rapid increase in the performance of graphics hardware, coupled with recent improvements in its programmability, have made graphics hardware a compelling platform for computationally demanding tasks in a wide variety of application domains. In this report, we describe, summarize, and analyze the latest research in mapping general-purpose computation to graphics hardware. We begin with the technical motivations that underlie general-purpose computation on graphics processors (GPGPU) and describe the hardware and software developments that have led to the recent interest in this field. We then aim the main body of this report at two separate audiences. First, we describe the techniques used in mapping general-purpose computation to graphics hardware. We believe these techniques will be generally useful for researchers who plan to develop the next generation of GPGPU algorithms and techniques. Second, we survey and categorize the latest developments in general-purpose application... https://escholarship.org/uc/item/9ns2d70c Fri, 28 Jun 2019 00:00:00 +0000 Owens, John D. Luebke, David Govindaraju, Naga Harris, Mark Krüger, Jens Lefohn, Aaron Purcell, Timothy J. https://escholarship.org/uc/item/9m79d7f0 This paper provides a basic overview of NURBS and their application to numerical grid generation. Curve/surface smoothing, accelerated grid generation, and the use of NURBS in a practical grid generation system are discussed. https://escholarship.org/uc/item/9m79d7f0 Fri, 28 Jun 2019 00:00:00 +0000 Barnhill, R. E. Farin, Gerald Hamann, Bernd https://escholarship.org/uc/item/9kt06678 Visualisierungstechniken zur Darstellung dreidimensionaler Datenmengen https://escholarship.org/uc/item/9kt06678 Fri, 28 Jun 2019 00:00:00 +0000 Hamann, Bernd https://escholarship.org/uc/item/9km0j5bc Arithmetic coding achieves a superior coding rate when encoding a binary source, but its lack of speed makes it an inferior choice when true high-performance encoding is needed. We present our work on a practical implementation of fast entropy coders for binary messages utilizing only bit shifts and table lookups. To limit code table size we limit our code lengths with a type of variable-to-variable (VV) length code created from source string merging. We refer to these codes as merged codes. With merged codes it is possible to achieve a desired level of speed by adjusting the number of bits read from the source at each step. The most efficient merged codes yield a coder with a worst-case inefficiency of 0.4%, relative to the Shannon entropy. Using a hybrid Golomb-VV Bin Coder we are able to achieve a compression ratio that is competitive with other state-of-the-art coders, at a superior throughput. https://escholarship.org/uc/item/9km0j5bc Fri, 28 Jun 2019 00:00:00 +0000 Senecal, Joshua Duchaineau, Mark A. Joy, Ken https://escholarship.org/uc/item/9jx0z501 Constructive mathematics is a philosophical doctrine that asserts that objects cannot be shown to exist unless a method is provided for producing them. The related usage Constructive Statistics is intended mean that statistical constructs, such as estimators, do not (usefully) exist unless they can be employed. A function defined from the data space to the parameter space is not an estimator by virtue of an existence proof, but only by virtue of a method for finding the answer. Furthermore, one cannot have a generally useful estimator unless it can be computed in a reasonable time (polynomial at a minimum). Asymptotics must be constrained by computational complexity. Another important point is that with many modern estimators that contain a stochastic component, the choice of algorithm determines the properties of the estimator. One could say that The Algorithm is the Estimator. Many of these modern stochastic estimators can be formulated as global optimization problems, with... https://escholarship.org/uc/item/9jx0z501 Fri, 28 Jun 2019 00:00:00 +0000 Rocke, David https://escholarship.org/uc/item/9jw53783 In this paper we present a system for visualizing volume data from remote supercomputers (PermWeb). We have developed both parallel volume rendering algorithms, and the World Wide Web software for accessing the data at the remote sites. The implementation uses Hypertext Markup Language (HTML), Java, and Common Gateway Interface (CGI) scripts to connect World Wide Web (WWW) servers/clients to our volume renderers. The front ends are interactive Java classes for specification of view, shading, and classification inputs. We present performance results, and implementation details for connections to our computing resources at the University of Cahfornia Santa Cruz including a MasPar MP-2, SGI Reality Engine-RE2,and SGI Challenge machines. We apply the system to the task of visualizing trabecular bone from finite element simulations. Fast volume rendering on remote compute servers through a web interface allows us to increase the accessibility of the results to more users. User interface... https://escholarship.org/uc/item/9jw53783 Fri, 28 Jun 2019 00:00:00 +0000 Wittenbrink, Craig M. Kwansik, Kim Story, Jeremy Pang, Alex Hollerbah, Karin Max, Nelson https://escholarship.org/uc/item/9jh8x8pm We describe the algorithms and data structures used for optimizing linear spline approximations of bivariate functions. Our method creates a random initial triangulation of a given data set and then employs a simulated annealing algorithm to improve this initial approximation. In every iteration step, the current approximation is changed in a random but local way, and the distance measure between it and the data is re-calculated. Depending on the difference between the old and new distance measures, an iteration step is either accepted or rejected.We discuss the basic operations and data structures of our optimization technique. We present a variant of the half-edge data structure and associated algorithms. https://escholarship.org/uc/item/9jh8x8pm Fri, 28 Jun 2019 00:00:00 +0000 Kreylos, Oliver Hamann, Bernd https://escholarship.org/uc/item/9j1903qn Adaptive mesh refinement (AMR) is a numerical simulation technique used in computational fluid dynamics (CFD). By using a set of nested grids of different resolutions, AMR combines the simplicity of structu red rectilinear grids with the ability to adapt to local changes in complexity in th e domain. Without proper interpolation on the boundaries of grids of different lev els of a hierarchy, discontinuities can arise. Treating locations of data values giv en at cell centers of AMR grids as vertices of a dual grid creates gaps between hierarchy levels. Using an index-based tessellation approach that fills these gaps with ``stitch cells'' we define an interpolation scheme that avoids discontinuities at level boundaries. We use the resulting interpolation scheme to generate volume-rendered images. Modifying transfer functions on a per-level basis allows us to emphasize (or de-emphasize) a specific level and gain a better understanding of the underlying hierarchical structure. https://escholarship.org/uc/item/9j1903qn Fri, 28 Jun 2019 00:00:00 +0000 Weber, Gunther H. Kreylos, Oliver Ligocki, Terry J. Shalf, John M. Hagen, Hans Hamann, Bernd Joy, Ken Ma, Kwan-Liu https://escholarship.org/uc/item/9hv9327j A new high-performance general-purpose graphics processing unit (GPGPU) computational fluid dynamics (CFD) library is introduced for use with structured-grid CFD algorithms. A novel set of parallel tridiagonal matrix solvers, implemented in CUDA, is included for use with structured-grid CFD algorithms. The solver library supports both scalar and block-tridiagonal matrices suitable for approximate factorization (AF) schemes. The computational routines are designed for both GPU-based CFD codes or as a GPU accelerator for CPU-based algorithms. Additionally, the library includes, among others, a collection of finite-volume calculation routines for computing local and global stable time-steps, inviscid surface fluxes, and face/node/cell-centered interpolation on generalized 3D, multi-block structured grids. GPU block tridiagonal benchmarks showed a speed-up of 3.6x compared to an OpenMP CPU Thomas Algorithm results when host-device data transfers are removed. Detailed analysis shows... https://escholarship.org/uc/item/9hv9327j Fri, 28 Jun 2019 00:00:00 +0000 Stone, Christopher P. Duque, Earl P. N. Zhang, Yao Car, David Owens, John D. Davis, Roger L. https://escholarship.org/uc/item/9h83s3m0 This paper presents a simple method for modeling and rendering refractive objects that are nested within each other. The technique allows the use of simpler scene geometry and can even improve rendering time in some images. The algorithm can be easily added into an existing ray tracer and makes no assumptions about the drawing primitives that have been implemented. https://escholarship.org/uc/item/9h83s3m0 Fri, 28 Jun 2019 00:00:00 +0000 Schmidt, Charles M. Budge, Brian C. https://escholarship.org/uc/item/9h1519cq We present an isosurface generation algorithm for large-scale volumetric scattered data. Rather than construct a global tessellation of the data points, we dene a set of local tetrahedrizations that are guaranteed to cover the domain. Inside each local tetrahedrization, a point-based isosurface contouring algorithm is applied to generate isosurface geometry. Our work differs from previous work in that we make very few assumptions about the density of the point distribution, and we construct visual representations of the data directly without global tessellation or resampling. The merit of such an approach is a fairly general method that produces faithful renderings of large-scale scientic data. https://escholarship.org/uc/item/9h1519cq Fri, 28 Jun 2019 00:00:00 +0000 Co, Christopher S. Joy, Ken https://escholarship.org/uc/item/9gv2n4m1 This paper discusses our efforts to improve the performance of the high-accuracy (HIAC) volume rendering system, based on cell projection, which is used to display unstructured, scientific data sets for analysis. The parallelization of HIAC, using the pthreads and MPI API's, resulted in significant speedup, but interactive frame rates are not yet attainable for very large data sets. https://escholarship.org/uc/item/9gv2n4m1 Fri, 28 Jun 2019 00:00:00 +0000 Bennett, Janine Cook, Richard Max, Nelson May, Deborah Williams, Peter https://escholarship.org/uc/item/9gm3f5t0 This thesis presents a new algorithm for material boundary interface reconstruction from data sets containing volume fractions. The reconstruction problem is transformed to a problem that analyzes the dual data set, where each vertex in the dual mesh has an associated barycentric coordinate tuple that represents the fraction of each material present. After constructing the dual tetrahedral mesh from the original mesh, material boundaries are constructed by mapping a tetrahedron into barycentric space and calculating the intersections with Voronoi cells in barycentric space. These intersections are mapped back to the original physical space and triangulated to form the boundary surface approximation. This algorithm can be applied to any grid structure and can treat any number of materials per element/vertex. It is a generalization of previous work done in other fields, allowing for any number of materials to be present in a given volume. This algorithm generates continuous surfaces.... https://escholarship.org/uc/item/9gm3f5t0 Fri, 28 Jun 2019 00:00:00 +0000 Bonnell, Kathleen S. https://escholarship.org/uc/item/9fq9g6fc The current state of the art in visualization research places a strong emphasis on different techniques to derive insight from disparate types of data. However, little work has investigated the visualization process itself. The information content of the visualization process---the results, history, and relationships between those results---is addressed by this work. A characterization of the visualization process is discussed, leading to a general model of the visualization exploration process. The model, based upon a new parameter derivation calculus, can be used for automated reporting, analysis, or visualized directly. An XML-based language for expressing visualization sessions using the model is also described. These sessions can then be shared and reused by collaborators. The model, along with the XML representation, provides an effective means to utilize the information within the visualization process to further data exploration. https://escholarship.org/uc/item/9fq9g6fc Fri, 28 Jun 2019 00:00:00 +0000 Jankun-Kelly, T. J. Ma, Kwan-Liu Gertz, Michael https://escholarship.org/uc/item/9fg082cg This paper introduces VScape, a virtual environment for intuitive, hand-based terrain design. We present a design environment that provides an intuitive interface for the creation and manipulation of 3D scenes as required for terrain, game-level and set design. VScape was developed to provide the user with maximum design flexibility while providing a small, yet powerful set of easy-to-use tools and functions. https://escholarship.org/uc/item/9fg082cg Fri, 28 Jun 2019 00:00:00 +0000 Hamann, Bernd Joy, Ken Kuester, Falko https://escholarship.org/uc/item/9f58n3qv The proper usage and creation of transfer functions for time-varying data sets is an often ignored problem in volume visualization. Although methods and guidelines exist for time-invariant data, little formal study for the time-varying case has been performed. This paper examines this problem, and reports the study that we have conducted to determine how the dynamic behavior of time-varying data may be captured by a single or small set of transfer functions. The criteria which dictate when more than one transfer function is needed were also investigated. Four data sets with different temporal characteristics were used for our study. Results obtained using two different classes of methods are discussed, along with lessons learned. These methods, including a new multi-resolution opacity map approach, can be used for semi-automatic generation of transfer functions to explore large-scale time-varying data sets. https://escholarship.org/uc/item/9f58n3qv Fri, 28 Jun 2019 00:00:00 +0000 Jankun-Kelly, T. J. Ma, Kwan-Liu https://escholarship.org/uc/item/9dw2x1dg Multiresolution representation of high-dimensional scattered data is a fundamental problem in scientific visualization. This paper introduces a data hierachy of Voronoi diagrams as a versatile solution. Given an arbitrary set of points in the plane, our goal is the construction of an approximation hierarhy using the Voronoi diagram as the essential building block. We have implemented two Voronoi diagram-based algorithms to demonstrate their usefulness for hierarchical scattered data approximation. The first algorithm uses a constant function to approximate the data within each Voronoi cell, and the second algorithm uses the Sibson interpolant [14]. https://escholarship.org/uc/item/9dw2x1dg Fri, 28 Jun 2019 00:00:00 +0000 Schussman, Shirley Bertram, Martin Hamann, Bernd Joy, Ken https://escholarship.org/uc/item/9dd6f376 Artificial neural networks are computer software or hardware models inspired by the structure and behavior of neurons in the human nervous system. As a powerful learning tool, increasingly neural networks have been adopted by many large-scale information processing applications but there is no a set of well defined criteria for choosing a neural network. The user mostly treats a neural network as a black box and cannot explain how learning from input data was done nor how performance can be consistently ensured. We have experimented with several information visualization designs aiming to open the black box to possibly uncover underlying dependencies between the input data and the output data of a neural network. In this paper, we present our designs and show that the visualizations not only help us design more efficient neural networks, but also assist us in the process of using neural networks for problem solving such as performing a classification task. https://escholarship.org/uc/item/9dd6f376 Fri, 28 Jun 2019 00:00:00 +0000 Tzeng, Fan-Yin Ma, Kwan-Liu https://escholarship.org/uc/item/9cg0w3q7 We implement an interactive 3D painting application that stores paint in an octree-like GPU-based adaptive data structure. Interactive painting of complex or unparameterized surfaces is an important problem in the digital film community. Many models used in production environments are either difficult to parameterize or are unparameterized implicit surfaces. We address this problem with a system that allows interactive 3D painting of complex, unparameterized models. The included movie demonstrates interactive painting of a 817k polygon model with effective paint resolutions varying between 64^3 to 2048^3. Our implementation differs from previous work in two important ways: first, it uses an adaptive data structure implemented entirely on the GPU, and second, it enables interactive performance with high quality by supporting quadlinear (mipmapped) filtering and fast, constant-time data accesses. https://escholarship.org/uc/item/9cg0w3q7 Fri, 28 Jun 2019 00:00:00 +0000 Kniss, Joe M. Lefohn, Aaron Strzodka, Robert Sengupta, Shubhabrata Owens, John D. https://escholarship.org/uc/item/9bg1z8n8 The design of very low bit rate coders, below 64 kilobits per second, presents a number of new challenges. Such low bit rate coders are targeted to small size images, say 176 X 144, or below and are limited to head and shoulders scenes. In this paper, we compare and rate the performance of several still image encoding methods such as DCT: Subband and Wavelets, using a new quality scale based on properties of human vision. These still image coders are embedded into video coders such as the H261 coder. The relative importance of intraframe and interframe quality and contributions to the total bit rate provide an overall design framework for these low bit rate video coders. We discuss and illustrate, for the encoding of low bit rate video. the still image and motion impairments that are perceptually most important. https://escholarship.org/uc/item/9bg1z8n8 Fri, 28 Jun 2019 00:00:00 +0000 Algazi, Ralph Hiwasa, N. https://escholarship.org/uc/item/99d0k1fg Auditory Localization Demonstrations https://escholarship.org/uc/item/99d0k1fg Fri, 28 Jun 2019 00:00:00 +0000 Duda, Richard O https://escholarship.org/uc/item/98z4d987 We present a systematic approach for direct volume rendering terascale-sized data that are time-varying, and possibly non-uniformly sampled, using only a single commodity graphics PC. Our method employs a data reduction scheme that combines lossless, wavelet-based progressive data access with a user-directed, hardware-accelerated data packing technique. Data packing is achieved by discarding data blocks with values outside the data interval of interest and encoding the remaining data in a structure that can be ef ciently decoded in the GPU. The compressed data can be transferred between disk, main memory, and video memory more ef ciently, leading to more effective data exploration in both spatial and temporal domains. Furthermore, our texture-map based volume rendering system is capable of correctly displaying data that are sampled on a stretched, Cartesian grid. To study the effectiveness of our technique we used data sets generated from a large solar convection simulation, computed... https://escholarship.org/uc/item/98z4d987 Fri, 28 Jun 2019 00:00:00 +0000 Akiba, Hiroshi Ma, Kwan-Liu Clyne, John https://escholarship.org/uc/item/985331m3 Efficient Parallel Scan Algorithms for Many-core GPUs https://escholarship.org/uc/item/985331m3 Fri, 28 Jun 2019 00:00:00 +0000 Sengupta, Shubhabrata Harris, Mark Garland, Michael Owens, John D. https://escholarship.org/uc/item/97w1g3vn For types of data visualization where the cost of producing images is high, and the relationship between the rendering parameters and the image produced is less than clear, a visual representation of the exploration process can make the process more eficient and effective. Image graphs represent not only the results but also the process of data visualization. Each node in an image graph consists of an image and the corresponding visualization parameters used to produce it. Each edge in a graph shows the change in rendering parameters between the two nodes it connects. Image graphs are not just static representations: users can interact with a graph to review a previous visualization session or to perform new rendering. Operations which cause changes in rendering parameters can propagate through the graph. The user can take advantage of the information in image graphs to understand how certain rendering parameter changes affect visualization results. Users can share the image graphs... https://escholarship.org/uc/item/97w1g3vn Fri, 28 Jun 2019 00:00:00 +0000 Ma, Kwan-Liu https://escholarship.org/uc/item/97k7x14x The Internet pervades many aspects of our lives and is becoming indispensable to critical functions in areas such as commerce, government, production and general information dissemination. To maintain the stability and efficiency of the Internet, every effort must be made to protect it against various forms of attacks, malicious uses, and errors. A key component in the Internet security effort is the routine examination of Internet routing data, which unfortunately can be too large and complicated to browse directly. We have developed an interactive visualization process which proves to be very effective for the analysis of Internet routing data. In this application paper, we show how each step in the visualization process helps direct the analysis and glean insights from the data. These insights include the discovery of patterns, detection of faults and abnormal events, understanding of event correlations, formation of causation hypotheses, and classification of anomalies. We... https://escholarship.org/uc/item/97k7x14x Fri, 28 Jun 2019 00:00:00 +0000 Teoh, Soon Tee Ma, Kwan-Liu Wu, Felix S. https://escholarship.org/uc/item/97b5m5pw The encoding of images at high quality is important in a number of applications. We have developed an approach to coding that produces no visible degradation and that we denote as perceptually transparent. Such a technique achieves a modest compression, but still significantly higher than error free codes. Maintaining image quality is not important in the early stages of a progressive scheme, when only a reduced resolution preview is needed. In this paper, we describe a new method for the progressive transmission of high quality still images, that efficiently uses the lower resolution images in the encoding process. Analysis based interpolation is used to estimate the higher resolution image, and reduces the incremental information transmitted at each step. This methodology for high quality image compression is also aimed at obtaining a compressed image of higher perceived quality that the original. https://escholarship.org/uc/item/97b5m5pw Fri, 28 Jun 2019 00:00:00 +0000 Algazi, Ralph Ford, Gary Estes, Robert R. El-Fallah, Adel https://escholarship.org/uc/item/979578gv The head-related transfer function (HRTF) for distant sources is a complicated function of azimuth, elevation and frequency. This paper presents simple geometric models of the head and torso that provide insight into its low-frequency behavior, especially at low elevations. The head-and-torso models are obtained by adding both spherical and ellipsoidal models of the torso to a classical spherical-head model. Two different numerical techniques--multipole reexpansion and boundary element methods--are used to compute the HRTF of the models in both the frequency domain and the time domain. These computed HRTFs quantify the characteristics of elevation-dependent torso reflections for sources above the torso-shadow cone, and reveal the qualitatively different effects of torso shadow for sources within the torso-shadow cone. These effects include a torso bright spot that is prominent for the spherical torso, and significant attenuation of frequencies above 1 kHz in a range of elevations.... https://escholarship.org/uc/item/979578gv Fri, 28 Jun 2019 00:00:00 +0000 Algazi, Ralph Duda, Richard O Duraiswami, R. Gumerov, A. Tang, Z. https://escholarship.org/uc/item/96z2629z Level set methods are a powerful tool for implicitly representing deformable surfaces. Since their inception, these techniques have been used to solve problems in fields as varied as computer vision, scientific visualization, computer graphics and computational physics. With the power and flexibility of this approach; however, comes a large computational burden. In the level set approach, surface motion is computed via a partial differential equation (PDE) framework. One possibility for accelerating level-set based applications is to map the solver kernel onto a commodity graphics processing unit (GPU). GPUs are parallel, vector computers whose power is currently increasing at a faster rate than that of CPUs. in this work, we demonstrate a GPU-based, three-dimensional level set solver that is capable of computing curvature flow as well as other speed terms. Results are shown for this solver segmenting the brain surface from an MRI data set. https://escholarship.org/uc/item/96z2629z Fri, 28 Jun 2019 00:00:00 +0000 Lefohn, Aaron Whitaker, Ross T. https://escholarship.org/uc/item/96x7p983 This paper discusses the constraints imposed by the path of a moving camera in multi-view sequential scene reconstruction scenarios such as in aerial video, which allow for an efficient detection and correction of inaccuracies in the feature tracking and structure computation processes. The main insight is that for short, planar segments of a continuous camera trajectory, parallax movement corresponding to a viewed scene point should ideally form a scaled and translated version of this trajectory when projected onto a parallel plane. Two inter-camera and intra-camera constraints arise, which create a prediction of where all feature tracks should be located given the consensus information of all accurate tracks and cameras, which allows for the detection and correction of inaccurate feature tracks, as well as a very simple update of scene structure. This procedure differs from classical approaches such as factorization and RANSAC. In both aerial video and turntable sequences, the... https://escholarship.org/uc/item/96x7p983 Fri, 28 Jun 2019 00:00:00 +0000 Hess-Flores, Mauricio Duchaineau, Mark A. Joy, Kenneth I. https://escholarship.org/uc/item/96m9h51j In this paper we describe an approach for the parameterization and modeling of objects represented by adaptive distance fields (ADFs). ADF's allow the construction of powerful solid modeling tools. They can represent surfaces of arbitrary and even changing topology, while providing a more intuitive modeling interface than control point based structures such as splines. Using the octree structure of ADFs, we build an adaptively refined quadrilateral mesh that is topologically equivalent to the object's surface. We then project the mesh onto the object using multiple projection and smoothing steps. The resulting mesh serves as the user interface for modeling iperations and is used for high quality rendering of the resulting shape. https://escholarship.org/uc/item/96m9h51j Fri, 28 Jun 2019 00:00:00 +0000 Bremer, Peer Timo Porumbescu, Serban D. Kuester, Falko Joy, Ken Hamann, Bernd https://escholarship.org/uc/item/94v8s29q Representation and Understanding of Scientific Data https://escholarship.org/uc/item/94v8s29q Fri, 28 Jun 2019 00:00:00 +0000 Konkle (Schussman), Shirley Ellen https://escholarship.org/uc/item/94t7x913 We present a method to aid in the generation of pen-and-ink style renderings of complex geometry. Most illustration algorithms focus on rendering a small number of surfaces with as much detail and expression as possible. These methods break down when the scene is composed of many small, overlapping details that are not individually resolvable. We propose a hybrid 2D/3D pipeline that incorporates image processing with the full scene geometry to extract regions which may require special handling. For silhouette renderings, grayscale value is matched to a sample rendering while preserving important edges and texture. For hatched areas, the approximate surface properties of each logical region is represented. The result is an image that is more clear for informative purposes, and more artistic for aesthetic purposes. https://escholarship.org/uc/item/94t7x913 Fri, 28 Jun 2019 00:00:00 +0000 Wilson, Brett Ma, Kwan-Liu https://escholarship.org/uc/item/94s9d3x6 It is useful to be able to define a two-dimensional point-set surface determined by a point cloud. One popular definition is Levin's MLS surface. This surface is defined on a domain which is a three-dimensional, a narrow region around the input point cloud. If we were to extend the definition outside the domain, we would produce components of the surface which are far from the point cloud. This is important in practice, since when moving points onto the MLS surface, we need to begin with an initial guess which is within the domain. We visualize the domain in two dimensions, and explain why it is so narrow. We also consider two MLS variants which can be defined on a wider domain without producing spurious surface components. One is efficient and works well except near sharp corners. The other is computationally expensive but seems to work well everywhere. https://escholarship.org/uc/item/94s9d3x6 Fri, 28 Jun 2019 00:00:00 +0000 Amenta, Nina Kil, Yong J https://escholarship.org/uc/item/937656xj We present an algorithm for computing the exact medial axis of a union of balls in IR[?]. Our algorithm combines the simple characterization of this medial axis given by Attali and Montanvert with the combinatorial information provided by Edelsbrunner's a-shape. This leads to a simple algorithm, which we have implemented for d=3 https://escholarship.org/uc/item/937656xj Fri, 28 Jun 2019 00:00:00 +0000 Amenta, Nina Kolluri, Ravi Krishna https://escholarship.org/uc/item/9347t2rx One of the grand challenges in computational biology is the prediction of the three-dimensional structure of a protein, which determines its function, from its chemical makeup alone. A protein's primary structure, i. e., its amino acid sequence, is directly encoded in its DNA sequence,which is a purely one-dimensional structure that does not directly encode a three-dimensional shape. It is commonly believed that the native shape of a protein is the one corresponding to the global minimum of its internal energy; thus, the protein folding problem has been treated as an optimization problem in recent years. It is important to start solving any optimization problem from a good set of initial configurations that allow the optimization code to, ideally, search the complete optimization space for a global minimum. Our work focuses on providing an interactive, visual tool to rapidly create many initial configurations for a given amino acid sequence, which are then used as input for... https://escholarship.org/uc/item/9347t2rx Fri, 28 Jun 2019 00:00:00 +0000 Kreylos, Oliver Hamann, Bernd Max, Nelson Bethel, Wes Crivelli, Silvia Noemi https://escholarship.org/uc/item/92x6j12c In this paper, we present a topological approach for simplifying continuous functions defined on volumetric domains. We introduce two atomic operations that remove pairs of critical points of the function and design a combinator ial algorithm that simplifies the Morse-Smale complex by repeated applicatio n of these operations. The Morse-Smale complex is a topological data structu re that provides a compact representation of gradient flow between critical points of a function. Critical points paired by the Morse-Smale complex iden tify topological features and their importance. The simplification procedure leaves important critical points untouched, and is therefore useful for ext racting desirable features. We also present a visualization of the simplifie d topology. https://escholarship.org/uc/item/92x6j12c Fri, 28 Jun 2019 00:00:00 +0000 Gyulassy, Attila Natarajan, Vijay Pascucci, Valerio Bremer, Peer Timo Hamann, Bernd https://escholarship.org/uc/item/92n6v1br We describe a hybrid data-representation and rendering technique for visualizing large-scale particle data generated from numerical modeling of beam dynamics. The basis of the technique is mixing volume rendering and point rendering according to particle density distribution, visibility, and the users instruction. A hierarchical representation of the data is created on a parallel computer, allowing real-time partitioning into high-density areas for volume rendering, and low-density areas for point rendering. This allows the beam to be interactively visualized while preserving the fine structure usually visible only with slow pointbased rendering techniques. https://escholarship.org/uc/item/92n6v1br Fri, 28 Jun 2019 00:00:00 +0000 Nguyen, Danh Rocke, David https://escholarship.org/uc/item/91v3246g Discussion of `Multivariate Outlier Detection and Robust Covariance Matrix Estimation https://escholarship.org/uc/item/91v3246g Fri, 28 Jun 2019 00:00:00 +0000 Rocke, David Woodruff, David https://escholarship.org/uc/item/8z55c86k In this paper, we develop optimum and suboptimum receivers for jointly detecting two cochannel continuous phase modulated (CPM) signals. These receivers are based upon Laurent's representation of binary CPM as a sum of a finite number of pulse amplitude modulated signals. We also provide a review of the Laurent representation and its application to the design of suboptimum single-channel receivers. https://escholarship.org/uc/item/8z55c86k Fri, 28 Jun 2019 00:00:00 +0000 Murphy, P. A. Ford, Gary https://escholarship.org/uc/item/8xv0237z We solve the problem of generating a uniform Poisson-disk sampling that is both maximal and unbiased over bounded non-convex domains. To our knowledge this is the first provably correct algorithm with time and space dependent only on the number of points produced. Our method has two phases, both based on classical dart-throwing. The first phase uses a background grid of square cells to rapidly create an unbiased, near-maximal covering of the domain. The second phase completes the maximal covering by calculating the connected components of the remaining uncovered voids, and by using their geometry to efficiently place unbiased samples that cover them. The second phase converges quickly, overcoming a common difficulty in dart-throwing methods. The deterministic memory is O(n) and the expected running time is O(n log n), where n is the output size, the number of points in the final sample. Our serial implementation verifies that the log n dependence is minor, and nearly O(n) performance... https://escholarship.org/uc/item/8xv0237z Fri, 28 Jun 2019 00:00:00 +0000 Ebeida, Mohamed S. Patney, Anjul Mitchell, Scott A. Davidson, Andrew Knupp, Patrick M. Owens, John D. https://escholarship.org/uc/item/8vx5n1z8 A Survey of Large High-Resolution Display Technologies, Techniques, and Applications https://escholarship.org/uc/item/8vx5n1z8 Fri, 28 Jun 2019 00:00:00 +0000 Ni, Tao Schmidt, Greg S. Staadt, Oliver G. Livingston, Mark A. Ball, Robert May, Richard https://escholarship.org/uc/item/8vv6b68h Image coding requires an effective representation of images to provide dimensionality reduction, a quantization strategy to maintain image quality, and finally the error free encoding of quantized coefficients. In the coding of quantized coefficients, Huffman coding and arithmetic coding have been used most commonly and are suggested as alternatives in the JPEG standard. In some recent work, zerotree coding has been proposed as an alternate method, that considers the dependence of of quantized coefficients from subband to subband, and thus appears as a generalization of the context-based approach often used with arithmetic coding. In this paper, we propose to review these approaches and discuss them as special cases of an analysis based approach to the coding of coefficients. The requirements on causality and computational complexity implied by arithmetic and zero-tree coding will be studied and other schemes proposed for the choice of the predictive coefficient contexts that... https://escholarship.org/uc/item/8vv6b68h Fri, 28 Jun 2019 00:00:00 +0000 Algazi, Ralph Estes, Robert R. https://escholarship.org/uc/item/8vd8n5sc We have studied the room temperature Raman spectra of several stages of ternary GICs prepared by sequential intercalation of potassium-binary GICs with either furan, THF or NH3. A Raman study, which detects the shift of the graphite intralayer vibrational frequency due to intercalation, provides a useful tool for the probe of charge transfer of these novel materials. For all three stage 1 compounds, we have observed an intralyer graphite vibrational frequency at ~1606 cm -1 (upshifted from the pure graphite peak at 1582 cm-1), which is Fano broadened and has a Raman profile similar to that exhibited by LiC6 and EuC6. These results are compared and contrasted with those for the alkali binary GICs. https://escholarship.org/uc/item/8vd8n5sc Fri, 28 Jun 2019 00:00:00 +0000 Solin, S. A. Vora Purohit, Parul York, B. R. https://escholarship.org/uc/item/8vd09323 In order to obtain insight into a complex vector field, it is often necessary to construct a hierarchical representation of the field. One way to construct such a hierarchy is based on grouping vectors together using certain similarity criteria. In this paper, we present a study of a 2D vector field clustering technique that is based on piecewise linear vector field approximations and an extension of a data clustering method called Normalized Cut (NC). Specifically, two steps are taken to implement the extended NC method. First, a similarity measurement for vector data is defined. Second, an eigenproblem solver is used to find the eigenvector used for partitioning. After the construction of first-level clusters, we can obtain a finer-level clustering by recursively applying the same procedure to intermediate clusters. The resulting clusters capture the features around the critical points. https://escholarship.org/uc/item/8vd09323 Fri, 28 Jun 2019 00:00:00 +0000 Chen, Jiann-Liang Bai, Zhaojun Ligocki, Terry J. https://escholarship.org/uc/item/8t2059vw Today's scientific and engineering problems require a different approach to address the massive data problems in organization, storage, transmission, visualization, exploration, and analysis. Visual techniques for data exploration are now common in many scientific, engineering, and business applications. However, the massive amount of data collected through simulation, collection and logging is inhibiting the use of conventional visualization methods. We need to discover new visualization methods that allow us to explore the massive multi-dimensional time-varying information streams and turn overwhelming tasks into opportunities for discovery and analysis. https://escholarship.org/uc/item/8t2059vw Fri, 28 Jun 2019 00:00:00 +0000 Joy, Ken https://escholarship.org/uc/item/8sv6s7n0 We present a simple and output optimal algorithm for accelerated isosurface extraction from volumetric data sets. Output optimal extraction algorithms perform an amount of work dominated by the size of the (output) isosurface rather than the size of the (input) data set. While several optimal methods have been proposed to accelerate isosurface extraction, these algorithms are relatively complicated to implement or require quantized values as input. Our method is based on a straightforward array data structure that only requires an auxiliary sorting routine for construction. The method works equally well for floating point data as it does for quantized data sets. We demonstrate how the data structure can exploit coherence between isosurfaces by performing searches incrementally. We show results for real application data validating the method's optimality. https://escholarship.org/uc/item/8sv6s7n0 Fri, 28 Jun 2019 00:00:00 +0000 Waters, Kenneth W. Co, Christopher S. Joy, Ken https://escholarship.org/uc/item/8s7004f3 Direct Volume Rendering (DVR) is commonly used to visualize scalar fiends. Quality and significance of rendered images depend on the choice of appropriate transfer functions that assigns optical properties (e.g., color and opacity) to scalar values. We present a method that automatically generates a transfer function based on the topology of a isosurface i.e., a surface representing all locations where the scalar fiend assumes a certain value v, changes. We then generate a transfer fucntion that emphasizes on scalar values around those critical isovalues. Images rendered using the resulting transfer function reveal the fundamental topogical structure of a scalar data set. https://escholarship.org/uc/item/8s7004f3 Fri, 28 Jun 2019 00:00:00 +0000 Weber, Gunther H. Scheuermann, Gerik https://escholarship.org/uc/item/8rt9h7b2 In this paper we describe a rendering method suitable for interactive previewing of large-scale arbitary-mesh volume data sets. A data set to be visualized is represented by a ''point cloud,'' i. e., a set of points and associated data values without known connectivity between the points. The method uses a multi-resolution approach to achieve interactive rendering rates of several frames per second for arbitrarily large data sets. Lower-resolution approximations of an original data set are created by iteratively applying a point- decimation operation to higher-resolution levels. The goal of this method is to provide the user with an interactive navigation and exploration tool to determine good viewpoints and transfer functions to pass on to a high-quality volume renderer that uses a standard algorithm. https://escholarship.org/uc/item/8rt9h7b2 Fri, 28 Jun 2019 00:00:00 +0000 Kreylos, Oliver Ma, Kwan-Liu Hamann, Bernd https://escholarship.org/uc/item/8pz0q5tn Low-frequency elevation-dependent features appear in HRTF measurements because of torso and shoulder reflections and head diffraction effects. A simple structural model that accounts for these features is presented. Listening tests show that the model produces significant elevation cues for virtual sound sources whose spectra are limited to frequencies below 3 KHz. The low-frequency binaural elevation cues are perceptually significant away form the madian plane, and complement high-freequency monaural pinna cues. https://escholarship.org/uc/item/8pz0q5tn Fri, 28 Jun 2019 00:00:00 +0000 Avendano, Carlos Algazi, Ralph Duda, Richard O https://escholarship.org/uc/item/8pb179vt We construct a graph on a planar point set, which captures its shape in the following sense: if a smooth curve is sampled densely enough, the graph on the samples is a polygonalization of the curve, with no extraeous edges. The required sampling density varies with the LOCAL FEATURE SIZE on the curve, so that area of less detail can be sampled less densely. We give two different graphs that, in this sense, reconstruct smooth curves: a simple new construction which we call the crust, and the B- skeleton, using a specific value of B. https://escholarship.org/uc/item/8pb179vt Fri, 28 Jun 2019 00:00:00 +0000 Amenta, Nina Bern, Marshall Eppstein, David https://escholarship.org/uc/item/8nv8g81q Chen and Williams[2]show how precomputed z-buffer images from different fixed viewing positions can be reprojected to produce an image for a new viewpoint. Here images are precomputed for twigs and branches at various levels in the hierarchical structure of a tree,and adaptively combined,depending on the position of the new viewpoint. The precomputed images contain multiple z levels to avoid missing pixels in the reconstruction, subpixel masks for antialiasing, and colors and normals for shading after reprojection. https://escholarship.org/uc/item/8nv8g81q Fri, 28 Jun 2019 00:00:00 +0000 Max, Nelson https://escholarship.org/uc/item/8n47c2d1 We develop and evaluate receiver signal processing algorithms for the detection of signals transmitted via the forward link of a cell in a cellular system modeled after the IS-95 standard for direct-sequence spread-spectrum code-division multiple-access (CDMA) communications. Multiuser detectors on board airborne and terrestrial mobile interceptors or monitors attempt the simultaneous detection, in a single receiver, of all communication signals transmitted by the base station of interest. Due to the detrimental effects of transmitter, reciever and channel nonlinearities, very fast multipath fading, shadowing, path loss, Doppler spread, additive white Gaussian noise, and intracell and intercell multiple-access interference, the user signals are de-orthogonalized. This leads to performance degradation in conventional receivers that is too severe, especially when the powers of some of the interfering users are dominant. In order to improve upon the performance of conventional... https://escholarship.org/uc/item/8n47c2d1 Fri, 28 Jun 2019 00:00:00 +0000 Golanbari, Michael Ford, Gary https://escholarship.org/uc/item/8mv656c5 We present a novel approach for analyzing two-dimensional (2D) flow field data based on the idea of invariant moments. Moment invariants have traditionally been used in computer vision applications, and we have adapted them for the pur pose of interactive exploration of flow field data. The new class of moment invariants we have developed allows us to extract and visualize 2D flow patterns, invariant under translation, scaling, and rotation. With our approach one can study arbitrar y flow patterns by searching a given 2D flow data set for any type of pattern as specified by a user. Further, our approach suppor ts the computation of moments at multiple scales, facilitating fast pattern extraction and recognition. This can be done for critical point classification, but also for patterns with greater complexity. This multi-scale moment representation is also valuable for the comparative visualization of flow field data. The specific novel contributions of the work presented are the... https://escholarship.org/uc/item/8mv656c5 Fri, 28 Jun 2019 00:00:00 +0000 Schlemmer, Michael Heringer, Manuel Morr, Florian Hotz, Ingrid Hering-Bertram, Martin Garth, Christoph Kollmann, Wolfgang Hamann, Bernd Hagen, Hans https://escholarship.org/uc/item/8kv3z3zs Prediction of Automotive Emissions from Gasoline Composition https://escholarship.org/uc/item/8kv3z3zs Fri, 28 Jun 2019 00:00:00 +0000 Rocke, David Pallas, Michelle https://escholarship.org/uc/item/8kr5977x While level sets have demonstrated a great potential for 3D medical image segmentation, their usefulness has been limited by two problems. First, 3D level sets are relatively slow to compute. Second, their formulation usually entails several free parameters which can be very difficult to correctly tune for specific applications. The second problem is compounded by the first. This paper presents a tool for 3D segmentation that relies on level-set surface models computed at interactive rates on commodity graphics cards (GPUs). The mapping of a level-set solver to a GPU relies on a novel mechanism for GPU memory management. The interactive rates for solving the level-set PDE give the user immediate feedback on the parameter settings, and thus users can tune three separate parameters and control the shape of the model in real time. We have found that this interactivity enables users to produce good, reliable segmentations. This paper presents qualitative and quantitative results... https://escholarship.org/uc/item/8kr5977x Fri, 28 Jun 2019 00:00:00 +0000 Lefohn, Aaron Cates, Joshua E. Whitaker, Ross T. https://escholarship.org/uc/item/8k7730px The Designer-Workbench project aims at transforming the classical industrial modeling and design paradigm into its virtual analog using state-of-the-art three dimensional I display technology, data gloves and spatial tracking. This paper outlines the fundamental tools and design paradigms required for the implementation of this modeling envirornment and demonstrates the usablility of virual environments (VEs) for simulation of two-handed clay modeling and design tasks on the basis of non uniform rational B-spines (NURBS) https://escholarship.org/uc/item/8k7730px Fri, 28 Jun 2019 00:00:00 +0000 Kuester, Falko Hamann, Bernd https://escholarship.org/uc/item/8k05z86n Integral surfaces are ideal tools to illustrate vector fields and fluid flow structures. However, these surfaces can be visually complex and exhibit difficult geometric properties, owing to strong stretching, shearing and folding of the flow from which they are derived. Many techniques for non-photorealistic rendering have been presented previously. It is, however, unclear how these techniques can be applied to integral surfaces. In this paper, we examine how transparency and texturing techniques can be used with integral surfaces to convey both shape and directional information. We present a rendering pipeline that combines these techniques aimed at faithfully and accurately representing integral surfaces while improving visualization insight. The presented pipeline is implemented directly on the GPU, providing real-time interaction for all rendering modes, and does not require expensive preprocessing of integral surfaces after computation. https://escholarship.org/uc/item/8k05z86n Fri, 28 Jun 2019 00:00:00 +0000 Hummel, Mathias Garth, Christoph Hamann, Bernd Hagen, Hans Joy, Ken https://escholarship.org/uc/item/8js4v3f7 We present a technique for designing memory-bound algorithms with high data reuse on Graphics Processing Units (GPUs) equipped with close-to-ALU software-managed memory. The approach is based on the efficient use of this memory through the implementation of a software-managed cache. We also present an analytical model for performance analysis of such algorithms. We apply this technique to the implementation of the GPU-based solver of the sum-product or marginalize a product of functions (MPF) problem, which arises in a wide variety of real-life applications in artificial intelligence, statistics, image processing, and digital communications. Our motivation to accelerate MPF originated in the context of the analysis of genetic diseases, which in some cases requires years to complete on modern CPUs. Computing MPF is similar to computing the chain matrix product of multi-dimensional matrices, but is more difficult due to a complex data-dependent access pattern, high data reuse,... https://escholarship.org/uc/item/8js4v3f7 Fri, 28 Jun 2019 00:00:00 +0000 Silberstein, Mark Schuster, Assaf Geiger, Dan Patney, Anjul Owens, John D. https://escholarship.org/uc/item/8jk3n8tc Experimentally measured head-related transfer functions reveal that the interaural time delay varies from person to person. Furthermore, it is not constant around a cone of confusion, but can vary by as much as 18% of the maximum interaural delay. The major sources for this variation are shown to be the shape of the head and the displacement of the ears from the center of the head. A simple ellipsoidal head model is presented that can accurately account for this ITD variation and can be adapted to individual listeners. https://escholarship.org/uc/item/8jk3n8tc Fri, 28 Jun 2019 00:00:00 +0000 Duda, Richard O Avendano, Carlos Algazi, Ralph https://escholarship.org/uc/item/8hr8p39w A new methodology for the determination of an objective metric for still image coding is reported. This methodology is applied to obtain a Picture Quality Scale (PQS) for the coding of achromatic images over the full range of image quality defined by the subjective Mean Opinion Score (MOS). This Picture Quality Scale takes into account the properties of visual perception for both global features and localized disturbances. PQS closely approximates the MOS, with a correlation coefficient of more than 0.92, as compared to 0.57 obtained using the conventional WMSE. Extensions and applications of the methodology and of the resulting metric are discussed. https://escholarship.org/uc/item/8hr8p39w Fri, 28 Jun 2019 00:00:00 +0000 Miyahara, M. Kotani, K. Algazi, Ralph https://escholarship.org/uc/item/8hn8q11f The recently introduced notion of Finite-Time Lyapunov Exponent to characterize Coherent Lagrangian Structures provides a powerful framework for the visualization and analysis of complex technical flows. Its definition is simple and intuitive, and it has a deep theoretical foundation. While the application of this approach seems straightforward in theory, the associated computational cost is essentially prohibitive. Due to the Lagrangian nature of this technique, a huge number of particle paths must be computed to fill the space-time flow domain. In this paper, we propose a novel scheme for the adaptive computation of FTLE fields in two and three dimensions that significantly reduces the number of required particle paths. Furthermore, for three-dimensional flows, we show on several examples that meaningful results can be obtained by restricting the analysis to a well-chosen plane intersecting the flow domain. Finally, we examine some of the visualization aspects of FTLE-based... https://escholarship.org/uc/item/8hn8q11f Fri, 28 Jun 2019 00:00:00 +0000 Garth, Christoph Gerhardt, Florian Tricoche, Xavier Hagen, Hans https://escholarship.org/uc/item/8hf4g09n In this paper we present a new technique for surface reconstruction of digitized models in three dimensions. Concerning this problem, we are given a data set in three-dimensional space, represented as a set of points without connectivity information, and the goal is to find, for a fixed number of vertices, a set of approxiamating triangles whic minimize the error measured by the displacement from the given points. Our method creates near-optimal linear spline approximations, using an iterative optimization scheme based on simulated annealing. The algorithm adapts the mesh to the data set and moves the triangles to enhance feature lines. At the end, we can use the approach to create a hierarchy of different resolutions for the model. https://escholarship.org/uc/item/8hf4g09n Fri, 28 Jun 2019 00:00:00 +0000 Hamann, Bernd Kreylos, Oliver Munno, G. Uva, Antony E. https://escholarship.org/uc/item/8h75v1gf We present a scalable volume rendering technique that exploits lossy compression and low-cost commodity hardware to permit highly interactive exploration of time-varying scalar volume data. A palette-based decoding technique and an adaptive bit allocation scheme are developed to fully utilize the texturing capability of a commodity 3-D graphics card. Using a single PC equipped with a modest amount of memory, a texture capable graphics card, and an inexpensive disk array, we are able to render hundreds of time steps of regularly gridded volume data (up to 42 millions voxels each time step) at interactive rates. By clustering multiple PCs together we demonstrate the data-size scalability of our method. The frame rates achieved make possible the interactive exploration of data in the temporal,spatial, and transfer function domains. A comprehensive evaluation of our method based on experimental studies using data sets (up to 134 millions voxels per time step) from turbulence flow... https://escholarship.org/uc/item/8h75v1gf Fri, 28 Jun 2019 00:00:00 +0000 Lum, Eric Ma, Kwan-Liu Clyne, John https://escholarship.org/uc/item/8h5134ht Isosurfaces are commonly used to visualize scalar fields. Critical isovalues indicate isosurface topology changes: the creation of new surface components, merging of surface components or the formation of holes in a surface component. Therefore, they highlight ``interesting'' isosurface behavior and are helpful in exploration of large trivariate data sets. We present a method that detects critical isovalues in a scalar field defined by piecewise trilinear interpolation over a rectilinear grid and describe how to use them when examining volume data. We further review varieties of the Marching Cubes (MC) algorithm, with the intention to preserve topology of the trilinear interpolant when extracting an isosurface. We combine and extend two approaches in such a way that it is possible to extract meaningful isosurfaces even when a critical value is chosen as isovalue. https://escholarship.org/uc/item/8h5134ht Fri, 28 Jun 2019 00:00:00 +0000 Weber, Gunther H. Scheuermann, Gerik Hamann, Bernd Hagen, Hans https://escholarship.org/uc/item/8gz6p6gj This paper describes work-in-progress on developing parallel visualization strategies for 3D Adaptive Mesh Refinement (AMR) data. AMR is a simple and powerful tool for modeling many important scientific and engineering problems. However, visualization tools for 3D AMR data are not generally available. Converting AMR data onto a uniform mesh would result in high storage requirements, and rendering the uniform-mesh data on an average graphics workstation can be painfully slow if not impossible. The adaptive nature of the embedded mesh demands sophisticated visualization calculations. In this work, we compare the performance and storage requirements of a parallel volume renderer for regular-mesh data with a new parallel renderer based on adaptive sampling. While both renderers can achieve interactive visualization, the new approach offers significant performance gains, as indicated by our experiments on the SGI/Cray T3E. https://escholarship.org/uc/item/8gz6p6gj Fri, 28 Jun 2019 00:00:00 +0000 Ma, Kwan-Liu https://escholarship.org/uc/item/8gx0d9gw Optical triangulation laser scanners produce errors at surface discontinuities and sharp features. These systematic errors are anisotropic. We examine the causes of these errors theoretically, and we study the correlation of systematic error with edge size and orientation experimentally. We then present a novel processing method for removing systematic errors, by combining scans taken at several different orientations. We apply an anisotropic filter to the separate scans, and use it to weight the data in a final combination step. Unlike previous approaches, our method does not require access to the scanner's internal data or firmware. We demonstrate the technique on data from laser range scanners by two different manufacturers. https://escholarship.org/uc/item/8gx0d9gw Fri, 28 Jun 2019 00:00:00 +0000 Abbasinejad, Fatemeh Kil, Yong J Sharf, Andri Amenta, Nina https://escholarship.org/uc/item/8gp0x7tc We develop a microbenchmark-based performance model for NVIDIA GeForce 200-series GPUs. Our model identifies GPU program bottlenecks and quantitatively analyzes performance, and thus allows programmers and architects to predict the benefits of potential program optimizations and architectural improvements. In particular, we use a microbenchmark-based approach to develop a throughput model for three major components of GPU execution time: the instruction pipeline, shared memory access, and global memory access. Because our model is based on the GPU's native instruction set, we can predict performance with a 5--15% error. To demonstrate the usefulness of the model, we analyze three representative real-world and already highly-optimized programs: dense matrix multiply, tridiagonal systems solver, and sparse matrix-vector multiply. The model provides us detailed quantitative analysis on performance, allowing us to understand the configuration of the fastest dense matrix multiply implementation... https://escholarship.org/uc/item/8gp0x7tc Fri, 28 Jun 2019 00:00:00 +0000 Zhang, Yao Owens, John D. https://escholarship.org/uc/item/8g591273 Head Related Transfer Functions (HRTF's) characterize the transformation of a sound source to the sounds reaching the eardrums, and are central to binaural hearing. Because they are the result of wave propagation and difiraction, they can only be approzimated by finitely parameterized filters. The functional dependence of the HRTF on azimuth und elevation is described, the requirements for a model are discussed, and e&sting models are reviewed. https://escholarship.org/uc/item/8g591273 Fri, 28 Jun 2019 00:00:00 +0000 Duda, Richard O https://escholarship.org/uc/item/8ff3512w For high quality applications, we have developed a coding technique that produces no visible degradation, that we denote as perceptually transparent. A compression significantly higher than error free codes is achieved. In a progressive scheme, a reduced resolution image is used for the transmission of high quality still images. To use the lower resolution images effectively, analysis based interpolation provides the estimate of the higher resolution image and reduces the incremental information transmitted. This approach may also lead to compressed images of higher quality that the original. https://escholarship.org/uc/item/8ff3512w Fri, 28 Jun 2019 00:00:00 +0000 Algazi, Ralph Ford, Gary Estes, Robert R. El-Fallah, Adel https://escholarship.org/uc/item/8f37d7sh We present a comparative visualization of the acoustic simulation results obtained by two different approaches that were combined into a single simulation algorithm. The first method solves the wave equation on a volume grid based on finite elements. The second method, phonon tracing, is a geometric approach that we have previously developed for interactive simulation, visualization and modeling of room acoustics. Geometric approaches of this kind are more efficient than FEM in the high and medium frequency range. For low frequencies they fail to represent diffraction, which on the other hand can be simulated properly by means of FEM. When combining both methods we need to calibrate them properly and estimate in which frequency range they provide comparable results. For this purpose we use an acoustic metric called gain and display the resulting error. Furthermore we visualize interference patterns, since these depend not only on diffraction, but also exhibit phase-dependent amplification... https://escholarship.org/uc/item/8f37d7sh Fri, 28 Jun 2019 00:00:00 +0000 Deines, Eduard Bertram, Martin Mohring, Jan Jegorovs, Jevgenij Michel, Frank Hagen, Hans Nielson, Gregory M. https://escholarship.org/uc/item/8dc9g25j We present a robust and efficient surface-surface intersection (SSI) algorithm. The algorithm is based on intersecting surface triangulations and improves the resulting linear spline curve approximations of the exact intersection curves by replacing intersecion points of the surface triangulations by exact intersecion points. We use a specialized data structure, the k-d tree, for the efficient intersection of surface triangulations. The resulting intersection curves are guaranteed to lie within a user-specified tolerance. https://escholarship.org/uc/item/8dc9g25j Fri, 28 Jun 2019 00:00:00 +0000 Jean, B. A. Hamann, Bernd https://escholarship.org/uc/item/8d88d3qc Human irises gain their appearance from a layered and highly complex structure that is difficult to model and render with conventional techniques. We present an approach that uses domain knowledge from the field of ocular prosthetics. In that field, ocularists create an artificial iris by painting many simple semi-transparent layers. We translate this methodology into a simple and effective toolkit which can be used to create and render realistic looking irises. https://escholarship.org/uc/item/8d88d3qc Fri, 28 Jun 2019 00:00:00 +0000 Lefohn, Aaron Caruso, Richard Reinhard, Erik Budge, Brian C. Shirley, Peter https://escholarship.org/uc/item/8ct0p8f9 The exploration of complex data sets requires interfaces to present and navigate through the visualization of the data. This abstract describes such an interface. https://escholarship.org/uc/item/8ct0p8f9 Fri, 28 Jun 2019 00:00:00 +0000 Jankun-Kelly, T. J. Ma, Kwan-Liu https://escholarship.org/uc/item/8cg1b19v We present a new visualization approach based on procedural grid generation for scattered data sets. Instead of pre-computing triangulations for a given set of levels in a data hierarchy, a triangulation within a specified region of interest (ROI) is computed by considering scattered data of a pre-computed scattered data hierarchy. By choosing an appropriate level in the hierarchy the number of samples representing the data set in the ROI can be kept sufficiently small to interactively generate a triangulation and a visualization of the data within the ROI. This allows one to generate the triangulation on-the-fly during the visualization process. https://escholarship.org/uc/item/8cg1b19v Fri, 28 Jun 2019 00:00:00 +0000 Weber, Gunther H. Heckel, Bjoern Hamann, Bernd Joy, Ken https://escholarship.org/uc/item/8cc6p8vr Deformable isosurfaces, implemented with level-set methods, have demonstrated a great potential in visualization for applications such as segmentation, surface processing, and surface reconstruction. Their usefulness has been limited, however, by two problems. First, 3D level sets are relatively slow to compute. Second, their formulation usually entails several free parameters that can be difficult to tune correctly for specific applications. The second problem is compounded by the first. This paper presents a solution to these challenges by describing graphics processor (GPU) based algorithms for solving and visualizing level-set solutions at interactive rates. Our efficient GPU-based solution relies on packing the level-set isosurface data into a dynamic, sparse texture format. As the level set moves, this sparse data structure is updated via a novel GPU to CPU message passing scheme. When the level-set solver is integrated with a real-time volume renderer operating on the same... https://escholarship.org/uc/item/8cc6p8vr Fri, 28 Jun 2019 00:00:00 +0000 Lefohn, Aaron Kniss, Joe M. Hansen, Charles D. Whitaker, Ross T. https://escholarship.org/uc/item/8bv9j7hn Most numerical simulations required techniques for the representation and munipulation of complex, three-dimensional geometries. This paper provides a short historical survey and an overview of state-of-the-art geometric modeling techniques and research issues, and dicusses a few selected applications of geometric modeling in computational areas. https://escholarship.org/uc/item/8bv9j7hn Fri, 28 Jun 2019 00:00:00 +0000 Farin, Gerald Hamann, Bernd https://escholarship.org/uc/item/89k672nm Adaptive mesh refinement (AMR) is a numerical simulation technique used in computational fluid dynamics (CFD). This technique permits efficient simulation of phenomena characterized by substantially varying scales in complexity. By using a set of nested grids of different resolutions, AMR combines the simplicity of structured rectilinear grids with the possibility to adapt to local changes in complexity within the domain of a numerical simulation that otherwise requires the use of unstructured grids. Without proper interpolation at the boundaries of the nested grids of different levels of a hierarchy, discontinuities can arise. These discontinuities can lead, for example, to cracks in an extracted isosurface. Treating locations of data values given at the cell centers of AMR grids as vertices of a dual grid allows us to use the original data values of the cell-centered AMR data in a marching-cubes (MC) isosurface extraction scheme that expects vertex centered data. The use of... https://escholarship.org/uc/item/89k672nm Fri, 28 Jun 2019 00:00:00 +0000 Weber, Gunther H. Kreylos, Oliver Ligocki, Terry J. Shalf, John M. Hagen, Hans Hamann, Bernd Joy, Ken https://escholarship.org/uc/item/895638fv Deformable isosurfaces, implemented with level-set methods, have demonstrated a great potential in visualization for applications such as segmentation, surface processing, and surface reconstruction. Their usefulness has been limited, however, by two problems. First, 3D level sets are relatively slow to compute. Second, their formulation usually entails several free parameters that can be difficult to tune correctly for specific applications. The second problem is compounded by the first. This paper presents a solution to these challenges by describing graphics processor (GPU) based algorithms for solving and visualizing level-set solutions at interactive rates. Our efficient GPU-based solution relies on packing the level-set isosurface data into a dynamic, sparse texture format. As the level set moves, this sparse data structure is updated via a novel GPU to CPU message passing scheme. When the level-set solver is integrated with a real-time volume renderer operating on the same... https://escholarship.org/uc/item/895638fv Fri, 28 Jun 2019 00:00:00 +0000 Lefohn, Aaron Kniss, Joe M. Hansen, Charles D. Whitaker, Ross T. https://escholarship.org/uc/item/88t4j38b We present a method for the iterative refinement of triangulations. Given a coarse triangulation of the compact domain of a bivariate function, we present a refinement strategy bsed on approximation error. The triangulation is used to compute a best linear spline approximation, using the term best approxiamation in an integral least squares sense. We improve an approximation by identifying the triangle with largest error and refine the triangulation by bisecting this triangle. https://escholarship.org/uc/item/88t4j38b Fri, 28 Jun 2019 00:00:00 +0000 Hamann, Bernd Jordan, Benjamin https://escholarship.org/uc/item/88p1b4db We present an out-of-core, point-based approach for interactive rendering of very large volumetric datasets. Our approach is based on the assumption that the density of voxels with the same function-value in large discretized volumetric scalar fields is high enough to be used to render contour and volume approximations using points to represent the voxels. This approach allows us to visualize isovalue-structures in high-resolution datasets at full resolution and interactive frame rates. In a pre-processing step, we sort the voxels by function-value and store them in a file together with a look-up table for later interactive retrieval. The displayed voxelsets can then be changed in real time by determining their locations in the file and loading them into memory. As we store position, and not function-value, the volumetric dimension of a dataset to be handled by our approach is limited by three factors: the number of points that can be rendered to achieve a sufficient frame rate,... https://escholarship.org/uc/item/88p1b4db Fri, 28 Jun 2019 00:00:00 +0000 Nuber, Christof Bruckschen, Ralph W. Hamann, Bernd Joy, Ken https://escholarship.org/uc/item/885515nq Much of the previous work in the large data visualization area has solely focused on handling the scale of the data. This task is clearly a great challenge and necessary, but it is not sufficient. Applying standard visualization techniques to large scale data sets often creates complicated pictures where meaningful trends are lost. A second challenge, then, is to also provide algorithms that simplify what an analyst must understand, using either visual or quantitative means. This challenge can be summarized as improving the legibility or reducing the complexity of massive data sets. Fully meeting both of these challenges is the work of many, many PhD dissertations. In this dissertation, we describe some new techniques to address both the scale and legibility challenges, in hope of contributing to the larger solution. In addition to our assumption of simultaneously addressing both scale and legibility, we add an additional requirement that the solutions considered fit well... https://escholarship.org/uc/item/885515nq Fri, 28 Jun 2019 00:00:00 +0000 Childs, Hank https://escholarship.org/uc/item/87w833vm The paper presents a technique for correcting discontinuites (holes, overlapping surfaces, and intersecting surfaces) in CAD data. The technique approximates faulty geometries by several new B-spline surfaces which match properly. Each B-spline surface is constructed from four user-defined boundary curves. https://escholarship.org/uc/item/87w833vm Fri, 28 Jun 2019 00:00:00 +0000 Jean, B. A. Hamann, Bernd