IEEE VIS Publication Dataset

Noise reduction is an important preprocessing step for many visualization techniques that make use of feature extraction. We propose a method for denoising 2-D vector fields that are corrupted by additive noise. The method is based on the vector wavelet transform and wavelet coefficient thresholding. We compare our wavelet-based denoising method with Gaussian filtering, and test the effect of these methods on the signal-to-noise ratio (SNR) of the vector fields before and after denoising. We also study the effect on relevant details for visualization, such as vortex measures. The results show that for low SNR, Gaussian filtering with large kernels has a somewhat higher performance than the wavelet-based method in terms of SNR. For larger SNR, the wavelet-based method outperforms Gaussian filtering. This is mostly due to the fact that Gaussian filtering tends to remove small details, which are preserved by the wavelet-based method.

Typically there is a high coherence in data values between neighboring time steps in an iterative scientific software simulation; this characteristic similarly contributes to a corresponding coherence in the visibility of volume blocks when these consecutive time steps are rendered. Yet traditional visibility culling algorithms were mainly designed for static data, without consideration of such potential temporal coherency. We explore the use of temporal occlusion coherence (TOC) to accelerate visibility culling for time-varying volume rendering. In our algorithm, the opacity of volume blocks is encoded by means of plenoptic opacity functions (POFs). A coherence-based block fusion technique is employed to coalesce time-coherent data blocks over a span of time steps into a single, representative block. Then POFs need only be computed for these representative blocks. To quickly determine the subvolumes that do not require updates in their visibility status for each subsequent time step, a hierarchical "TOC tree" data structure is constructed to store the spans of coherent time steps. To achieve maximal culling potential, while remaining conservative, we have extended our previous POP into an optimized POP (OPOP) encoding scheme for this specific scenario. To test our general TOC and OPOF approach, we have designed a parallel time-varying volume rendering algorithm accelerated by visibility culling. Results from experimental runs on a 32-processor cluster confirm both the effectiveness and scalability of our approach.

The automotive industry demands visual support for the verification of the quality of their products from the design phase to the manufacturing phase. This implies the need of tools for measurement planning, programming measuring devices, managing measurement data, and the visual exploration of the measurement results. To improve the quality control throughout the whole process chain an integration of such tools in a platform independent framework is crucial. We present eMMA (enhanced Measure Management Application), a client/server system integrating measurement planning, data management, and straightforward as well as sophisticated visual exploration tools in a single framework.

Grid computing provides a challenge for visualization system designers. In this research, we evolve the dataflow concept to allow parts of the visualization process to be executed remotely in a secure and seamless manner. We see dataflow at three levels: an abstract specification of the intent of the visualization; a binding of these abstract modules to a specific software system; and then a binding of software to processing and other resources. We develop an XML application capable of describing visualization at the three levels. To complement this, we have implemented an extension to a popular visualization system, IRIS Explorer, which allows modules in a dataflow pipeline to run on a set of grid resources. For computational steering applications, we have developed a library that allows a visualization system front-end to connect to a simulation running remotely on a grid resource. We demonstrate the work in two applications: the dispersion of a pollutant under different wind conditions; and the solution of a challenging numerical problem in elastohydrodynamic lubrication.

Vortex breakdowns and flow recirculation are essential phenomena in aeronautics where they appear as a limiting factor in the design of modern aircrafts. Because of the inherent intricacy of these features, standard flow visualization techniques typically yield cluttered depictions. The paper addresses the challenges raised by the visual exploration and validation of two CFD simulations involving vortex breakdown. To permit accurate and insightful visualization we propose a new approach that unfolds the geometry of the breakdown region by letting a plane travel through the structure along a curve. We track the continuous evolution of the associated projected vector field using the theoretical framework of parametric topology. To improve the understanding of the spatial relationship between the resulting curves and lines we use direct volume rendering and multidimensional transfer functions for the display of flow-derived scalar quantities. This enriches the visualization and provides an intuitive context for the extracted topological information. Our results offer clear, synthetic depictions that permit new insight into the structural properties of vortex breakdowns.

In this paper we offer methods for visualization of the formation of nanoparticles in turbulent flows. We present the use of pointillism as a technique to convey the distribution of nanoparticle sizes as texture in an area. We also demonstrate a method of producing and packing spot glyphs representative of the distribution of nanoparticle sizes at every point in the flow to produce an intuitive and extensible framework for the visualization.

An important challenge encountered during post-processing of finite element analyses is the visualizing of three-dimensional fields of real-valued second-order tensors. Namely, as finite element meshes become more complex and detailed, evaluation and presentation of the principal stresses becomes correspondingly problematic. In this paper, we describe techniques used to visualize simulations of perturbed in-situ stress fields associated with hypothetical salt bodies in the Gulf of Mexico. We present an adaptation of the Mohr diagram, a graphical paper and pencil method used by the material mechanics community for estimating coordinate transformations for stress tensors, as a new tensor glyph for dynamically exploring tensor variables within three-dimensional finite element models. This interactive glyph can be used as either a probe or a filter through brushing and linking.

Researchers in computational condensed matter physics deal with complex data sets consisting of time varying 3D tensor, vector, and scalar quantities. Particularly, in the research of topological defects in nematic liquid crystals (LC) displaying the results of the computer simulation of molecular dynamics presents a challenge. Combining existing immersive and interactive visualization methods we developed new methods that attempt to provide a clear, efficient, and intuitive way to visualize and explore LC data. In addition, the visualization of the data has presented us with a novel method of obtaining the locations of the topological defects present in a liquid crystal system.

We present a system for enhancing observation of user interactions in virtual environments. In particular, we focus on analyzing behavior patterns in the popular team-based first-person perspective game Return to Castle Wolfenstein: Enemy Territory. This game belongs to a genre characterized by two moderate-sized teams (usually 6 to 12 players each) competing over a set of objectives. Our system allows spectators to visualize global features such as large-scale behaviors and team strategies, as opposed to the limited, local view that traditional spectating modes provide. We also add overlay visualizations of semantic information related to the action that might be important to a spectator in order to reduce the information overload that plagues traditional overview visualizations. These overlays can visualize information about abstract concepts such as player distribution over time and areas of intense combat activity, and also highlight important features like player paths, fire coverage, etc. This added information allows spectators to identify important game events more easily and reveals large-scale player behaviors that might otherwise be overlooked.

Waves are a fundamental mechanism for conveying information in many physical problems. Direct visualization techniques are often used to display wave fronts. However, the information derived from such visualizations may not be as central to an investigation as an understanding of how the location, structure and time course of the wave change as key experimental parameters are varied. In experimental data, these questions are confounded by noise and incomplete data. Recognition of waves in networks of neurons is additionally complicated by the presence of long-range physical connections and recurrent excitation. This work applies visual techniques to analyze the structural details of waves in response data from the turtle visual cortex. We emphasize low-cost visualizations that allow comparisons across neural data sets and variables to reconstruct the choreography for a complex response.

The continuing advancement of plasma science is central to realizing fusion as an inexpensive and safe energy source. Gryokinetic simulations of plasmas are fundamental to the understanding of turbulent transport in fusion plasma. This work discusses the visualization challenges presented by gyrokinetic simulations using magnetic field line following coordinates, and presents an effective solution exploiting programmable graphics hardware to enable interactive volume visualization of 3D plasma flow on a toroidal coordinate system. The new visualization capability can help scientists better understand three-dimensional structures of the modeled phenomena. Both the limitations and future promise of the hardware-accelerated approach are also discussed.

We present the current state of Vol-a-Tile, an interactive tool for exploring large volumetric data on scalable tiled displays. Vol-a-Tile presents a variety of features employed by scientists at the Scripps Institution of Oceanography on data collected from the Anatomy of a Ridge-Axis Discontinuity seismic experiment. Hardware texture mapping and level-of-detail techniques provide interactivity. A high-performance network protocol is used to connect remote data sources over high-bandwidth photonic networks.

We propose an interpolating refinement method for two- and three-dimensional scalar fields defined on hexahedral grids. Iterative fairing of the underlying contours (isosurfaces) provides the function values of new grid points. Our method can be considered as a nonlinear variational subdivision scheme for volumes. It can be applied locally for adaptive mesh refinement in regions of high geometric complexity. We use our scheme to increase the quality of low-resolution data sets and to reduce interpolation artifacts in texture-based volume rendering.