Fig. 1. Sample rendering of a plume vector field dataset using our streamline selection technique. Our technique is able to depict the interesting data features in a view-dependent fashion while avoiding self-occlusion from the streamlines, and does not require any user intervention.Abstract-This paper introduces a new streamline placement and selection algorithm for 3D vector fields. Instead of considering the problem as a simple feature search in data space, we base our work on the observation that most streamline fields generate a lot of self-occlusion which prevents proper visualization. In order to avoid this issue, we approach the problem in a view-dependent fashion and dynamically determine a set of streamlines which contributes to data understanding without cluttering the view. Since our technique couples flow characteristic criteria and view-dependent streamline selection we are able achieve the best of both worlds: relevant flow description and intelligible, uncluttered pictures. We detail an efficient GPU implementation of our algorithm, show comprehensive visual results on multiple datasets and compare our method with existing flow depiction techniques. Our results show that our technique greatly improves the readability of streamline visualizations on different datasets without requiring user intervention.
In this paper we present a multi-GPU parallel volume rendering implemention built using the MapReduce programming model. We give implementation details of the library, including specific optimizations made for our rendering and compositing design. We analyze the theoretical peak performance and bottlenecks for all tasks required and show that our system significantly reduces computation as a bottleneck in the ray-casting phase. We demonstrate that our rendering speeds are adequate for interactive visualization (our system is capable of rendering a 1024 3 floating-point sampled volume in under one second using 8 GPUs), and that our system is capable of delivering both in-core and out-of-core visualizations. We argue that a multi-GPU MapReduce library is a good fit for parallel volume renderering because it is easy to program for, scales well, and eliminates the need to focus on I/O algorithms thus allowing the focus to be on visualization algorithms instead. We show that our system scales with respect to the size of the volume, and (given enough work) the number of GPUs.
Finding correlations among data is one of the most essential tasks in many scientific investigations and discoveries. This paper addresses the issue of creating a static volume classification that summarizes the correlation connection in time-varying multivariate data sets. In practice, computing all temporal and spatial correlations for large 3D time-varying multivariate data sets is prohibitively expensive. We present a sampling-based approach to classifying correlation patterns. Our sampling scheme consists of three steps: selecting important samples from the volume, prioritizing distance computation for sample pairs, and approximating volume-based correlation with sample-based correlation. We classify sample voxels to produce static visualization that succinctly summarize the connection among all correlation volumes with respect to various reference locations. We also investigate the error introduced by each step of our sampling scheme in terms of classification accuracy. Domain scientists participated in this work and helped us select samples and evaluate results. Our approach is generally applicable to the analysis of other scientific data where correlation study is relevant.
DE82 017 025 Hy drogen and deuterium fluxes parallel to the t o roidal ma gnetic field were measured in the plasma boundary of ASDEX using graphite collector probes. Time resolution of the order of 100 ms can be obtained by rotating the cylindrical pro bes behind an aperture during the discharge. The trapped amount of hydrogen was determined by subsequent thermal desorption; in the. analyses of deuterium the D(3 He,p) 4 He
This paper presents visualization of field-measured, time-varying multidimensional earthquake accelerograph readings. Direct volume rendering is used to depict the space-time relationships of seismic readings collected from sensor stations in an intuitive way such that the progress of seismic wave propagation of an earthquake event can be directly observed. The resulting visualization reveals the sequence of seismic wave initiation, propagation, attenuation over time, and energy releasing events. We provide a case study on the magnitude scale M w 7.6 Chi-Chi earthquake in Taiwan, which is the most thoroughly recorded earthquake event ever in the history. More than 400 stations recorded this event, and the readings from this event increased global strong-motion records five folds. Each station measured east-west, north-south, and vertical component of acceleration for approximately 90 seconds. The sensor network released the initial raw data within minutes after the ChiChi mainshock. It is essential to have a visualization system for fast data exploring and analyzing, offering crucial visual analytical information for scientists to make quick judgments. Raw data requires preprocessing before it can be rendered. We generated a sequence of ground-motion wave-field maps of 350 × 200 regular grid covers the entire Taiwan island from the sensor network readings. The result is a total of 1000 ground-motion wave-field maps with 0.1 second interval, forming a 1000 × 350 × 200 volume data set. We show that visualizing the time-varying component of the data spatially uncovers the changing features hidden in the data.
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