基于图像的大规模数据集交互可视化

随着计算机性能的不断提高,大规模数值模拟的规模成倍增长.即使在大型可视化服务器上,针对这些模拟结果的大规模数据可视分析也难以进行流畅地交互.提出基于图像的交互分析方法并开发相应系统,可以预先生成多视角的可视化结果图像,基于这些图像可以在普通设备上实现3D可视化结果的交互分析与展示,可以交互改变观察视角,动态展示数值模拟全过程的可视化结果,可以有效提高数值模拟的效率.     

基于图象的交互绘制和数据压缩

体数据的绘制速度是交互可视化的瓶颈。将基于图象的绘制方法和传统的体绘制方法相结合,提出了一个新的基于图象的快速图形图象绘制系统,大大提高了体数据交互可视化的速度。该方法首先用传统的体绘制方法得到一列采样图象,然后根据图象间象素的冗合性,通过Ｗａｒｐｉｎｇ变换压缩数据,由压缩后的数据Ｗａｒｐｉｎｇ生成任意视点的视图。为了进一步提高计算速度,给出了递推Ｗａｒｐｉｎｇ变换计算流程。     

Data Visualization: Featuring Interactive Visual Analysis

Data visualization is an application‐driven field, that is always trying to satisfy its customers and to adapt to the demands, cultures, and workflows of many application areas. Therefore, it is difficult to keep focus on techniques and approaches that are not too application specific. A lot of good work on data visualization consists of single‐problem solutions, that cannot be easily merged into general‐purpose systems. In this talk, I will briefly review some current trends and issues, and identify some approaches that are common to many applications. One such approach in data visualization that has attracted interest from the early days is the detection of salient features, or patterns of interest in a data set. The main idea is to extract information at a higher level of abstraction from a mass of data, that is richer in semantics but much smaller in size, and that can help to define scenes and objects for visualization. This idea was pioneered in areas such as flow visualization, but is now more widely applied. It is often considered to be necessity to keep up with the ever rapidly increasing size of data sets, and the demand for interactivity in data visualization and analysis. Another generic approach in data visualization is called interactive visual analysis (TVA), consisting of a strongly interactive multiple‐linked‐view interfaces with integrated, powerful data analysis techniques taken from statistical analysis, pattern recognition, machine learning, and other fields. This is built on the assumptions that a single 2D or 3D visualization is often not enough, and spatial views can be augmented with abstract, derived data spaces; that strong interaction helps to promote insight; and that a better balance is needed between human visual inspection and computer‐based analysis and reasoning. Interestingly, an IVA interface can serve not only as an environment for exploration of low‐level data, but also for defining the high‐level features to be extracted, that should summarize the essence of the data. The high‐level features are usually highly application specific, and can only be found using theories from the application domains. The big challenge is to create environments for general purpose visual data analysis, and yet allow users to introduce advanced theories and methods from many application domains. The trend towards more integration in data visualization will be illustrated with cross‐links between very different areas, such as medical and flow visualization, and the combined use of techniques from scientific visualization and information visualization, and the absorption of other data analysis techniques. Also, historic and contemporary examples of feature extraction and interactive visual analysis will be shown.     

多角度可交互的多维数据可视化方法

提出一种多维数据的可视化方法“旋转坐标系折线法”,通过将Fisheye与星型法相结合,增强可交互性。针对不同可视化技术的特点,提出多角度交互连线法(MCA),将多种可视化方案相结合,从不同角度可视化多维数据。实验证明,该可视化方法可以分析数据进行聚类,评价聚类的准确性与可靠性,也能与用户灵活交互,可更清晰地将可视化效果呈现给用户。该方法已应用于EFCS_Grid网格系统中,达到了预期目标。     

一个基于 Google Earth 的交互式空间体数据可视化系统

三维空间体数据的可视化既需要同时展示数据多个属性的特征,又需要结合数据周边复杂地理地貌的特征。体绘制是当前最有效的三维数据可视化方法之一,但现有的体绘制方法尚没有考虑到数据场周围复杂的地理地貌特征。本文提出了一种基于 Google Earth (简称 GE) 地理信息的空间数据体绘制可视化方法,其基本思想是首先由三维纹理算法出发,对数据做沿高度法向的切片,多层渲染后组合为最终的体绘制效果,然后将渲染结果转换为 GE 支持的 KML 数据格式,充分利用 GE 中的复杂地形和三维建筑群模型信息,最后加入体感控制和 WEB 呈现功能。这为三维空间数据的可视化提供了一种全新的思路,取得了更好的可视化效果。最后利用数值模拟的大气雾霾数据论证了技术的可行性。     

JaVis系统中的多分辨数据组织与交互可视化

随着高性能计算机以及相关软硬件技术的飞速发展,数值模拟的规模越来越大,置信度越来越高,其产生的数据场规模亦越来越大、越来越复杂,需要更高级的科学计算可视化方法分析这些数值计算结果.然而,针对目前的TB级以及更大规模教据场,可视化的交互性能迟滞落后,成为阻碍数据分析的重要因素.如何提高可视化分析的交互速度,减少数据场的I/O处理是目前可视化系统必须解决的重要问题.多分辨技术是解决大规模数据场交互可视化的重要手段之一.自研发的大规模并行分布式数据分析与可视化系统JaVis采用多分辨技术提高数据可视化的交互速度,其中实现的关键技术如下:多分辨数据的组织、多分辨控制插件的生成、多分辨率层次切换技术等,并利用物理科学数据进行了性能及可靠性测试.     

交互式数据可视化软件开发系统的设计与实现

ＩＤＶＴ１．０是运行于ＰＣ平台的交互式数据可视化软件开发系统,其核心是用于绘制科学计算数据、商业统计图形、多边形模型的对象库。使用ＩＤＶＴ１．０,程序员可以快速开发交互式数据可视化应用软件。该文论述ＩＤＶＴ １．０的系统设计与实现：（１）对象的内存管理;（２）三维交互设计;（３）三维坐标的数据标注。     

Interactive Visualization of Multimodal Volume Data for Neurosurgical Tumor Treatment

We present novel interactive methods for the visualization of multimodal volume data as used in neurosurgical therapy planning. These methods allow surgeons to explore multimodal volumes and focus on functional data and lesions. Computer graphics techniques are proposed to create expressive visualizations at interactive frame rates to reduce time‐consuming and complex interaction with the medical data. Contributions of our work are the distance‐based enhancements of functional data and lesions which allows the surgeon to perceive functional and anatomical structures at once and relate them directly to the intervention. In addition we propose methods for the visual exploration of the path to the structures of interest, to enhance anatomical landmarks, and to provide additional depth indicators. These techniques have been integrated in a visualization prototype that provides interaction capabilities for finding the optimal therapeutic strategy for the neurosurgeon.     

A Quick Rendering Method Using Basis Functions for Interactive Lighting Design

When designing interior lighting effects, it is desirable to compare a variety of lighting designs involving different lighting devices and directions of light. It is, however, time-consuming to generate images with many different lighting parameters, taking interreflection into account, because all luminances must be calculated and recalculated. This makes it difficult to design lighting effects interactively. To address this problem, this paper proposes a method of quickly generating images of a given scene illustrating an interreflective environment illuminated by sources with arbitrary luminous intensity distributions. In the proposed method, the luminous intensity ditribution is expressed with basis functions. The proposed method uses a series of spherical harmonic functions as basis functions, and calculates in advance each intensity on surfaces lit by the light sources whose luminous intensity distribution are the same as the spherical harmonic functions. The proposed method makes it possible to generate images so quickly that we can change the luminous intensity distribution interactively. Combining the proposed method with an interactive walk-through that employs intensity mapping, an interactive system for lighting design is implemented. The usefulness of the proposed method is demonstrated by its application to interactive lighting design, where many images are generated by altering lighting devices and/or direction of light.     

Interactive Visualization with Programmable Graphics Hardware

One of the main scientific goals of visualization is the development of algorithms and appropriate data models which facilitate interactive visual analysis and direct manipulation of the increasingly large data sets which result from simulations running on massive parallel computer systems, from measurements employing fast high‐resolution sensors, or from large databases and hierarchical information spaces. This task can only be achieved with the optimization of all stages of the visualization pipeline: filtering, compression, and feature extraction of the raw data sets, adaptive visualization mappings which allow the users to choose between speed and accuracy, and exploiting new graphics hardware features for fast and high‐quality rendering. The recent introduction of advanced programmability in widely available graphics hardware has already led to impressive progress in the area of volume visualization. However, besides the acceleration of the final rendering, flexible graphics hardware is increasingly being used also for the mapping and filtering stages of the visualization pipeline, thus giving rise to new levels of interactivity in visualization applications. The talk will present recent results of applying programmable graphics hardware in various visualization algorithms covering volume data, flow data, terrains, NPR rendering, and distributed and remote applications.     

在连续框架下利用拓扑特征增强的体数据可视化

传统体绘制方法难以清晰地展现体数据的内部结构,本文提出了基于连续框架的利用数据拓扑特征增强体绘制的新方法.该方法首先利用7方向box样条拟插值对离散数据进行连续重建,然后通过求解多项式系统得到数据场中的特征点分布;从鞍点出发可以在连续模型上计算出鞍极曲线,本文提出以鞍极曲线长度给特征点值分布加权得到含权特征点直方图,并依据直方图信息重新设计体绘制的传输函数来增强体绘制.实验结果表明,与离散框架的方法相比,文中方法更加简单可靠,且可视化结果具有更好的平滑性,能清晰地反映体数据内部的细微结构.     

Interactive Visualization of Implicit Surfaces with Singularities

This paper presents work on two methods for interactive visualization of implicit surfaces: physically-based sampling using particle systems and polygonization followed by physically-based mesh improvement which explicitly makes use of the surface-defining equation. While most previous work applied to bounded manifolds without singularities and without boundary (topological spheres) we broaden the scope of the methods to include surfaces with such features, in particular cusp points and surface self-intersections. These aspects are not (yet) essential for computer graphics modelling with implicit surfaces but they naturally occur in simulations of interest in mathematical visualization. In this paper we use the Kummer family of algebraic surfaces as an example.     

Numerical Cubature on Scattered Data by Radial Basis Functions

We study cubature formulas on relatively small scattered samples in the unit square, obtained by integrating radial basis function (RBF) interpolants. Numerical tests show that, due to the small size of the corresponding weights (which are not all positive in general), thin-plate splines and Wendland's compactly supported radial functions give the most reliable RBF cubature methods.     

Large Scattered Data Fitting Based on Radial Basis Functions

Solving large radial basis function （RBF） interpolation problem with non-customized methods is computationally expensive and the matrices that occur are typically badly conditioned. In order to avoid these difficulties, we present a fitting based on radial basis functions satisfying side conditions by least squares, although compared with interpolation the method loses some accuracy, it reduces the computational cost largely. Since the fitting accuracy and the non-singularity of coefficient matrix in normal equation are relevant to the uniformity of chosen centers of the fitted RBE we present a choice method of uniform centers. Numerical results confirm the fitting efficiency.     

Time‐Adaptive Lines for the Interactive Visualization of Unsteady Flow Data Sets

The quest for the ideal flow visualization reveals two major challenges: interactivity and accuracy. Interactivity stands for explorative capabilities and real‐time control. Accuracy is a prerequisite for every professional visualization in order to provide a reliable base for analysis of a data set. Geometric flow visualization has a long tradition and comes in very different flavors. Among these, stream, path and streak lines are known to be very useful for both 2D and 3D flows. Despite their importance in practice, appropriate algorithms suited for contemporary hardware are rare. In particular, the adaptive construction of the different line types is not sufficiently studied. This study provides a profound representation and discussion of stream, path and streak lines. Two algorithms are proposed for efficiently and accurately generating these lines using modern graphics hardware. Each includes a scheme for adaptive time‐stepping. The adaptivity for stream and path lines is achieved through a new processing idea we call ‘selective transform feedback’. The adaptivity for streak lines combines adaptive time‐stepping and a geometric refinement of the curve itself. Our visualization is applied, among others, to a data set representing a simulated typhoon. The storage as a set of 3D textures requires special attention. Both algorithms explicitly support this storage, as well as the use of precomputed adaptivity information.     

Interactive Fusion and Tracking For Multi‐Modal Spatial Data Visualization

Scientific data acquired through sensors which monitor natural phenomena, as well as simulation data that imitate time‐identified events, have fueled the need for interactive techniques to successfully analyze and understand trends and patterns across space and time. We present a novel interactive visualization technique that fuses ground truth measurements with simulation results in real‐time to support the continuous tracking and analysis of spatiotemporal patterns. We start by constructing a reference model which densely represents the expected temporal behavior, and then use GPU parallelism to advect measurements on the model and track their location at any given point in time. Our results show that users can interactively fill the spatio‐temporal gaps in real world observations, and generate animations that accurately describe physical phenomena.     

基于直接体绘制的三维数据场交互可视化系统SinoVis

文中描述了基于直接体绘制的三维数据场交互可视化系统SinoVis的系统设计框架与具体实现。SinoVis是一个纯软件的可视化分析系统,SinoVis绘制的图像精细,可视化参数的设置与调整方便灵活,可以在任意选择的体元分类转移函数下对规模为128^3～256^3的体数据实现高速交互绘制,在相当广泛的研究与工程领域里有潜在的应用价值。     

Interactive Fibre Structure Visualization of the Heart

The heart consists of densely packed muscle fibres. The orientation of these fibres can be acquired by using Diffusion Tensor Imaging (DTI) ex vivo. A good way to visualize the fibre structure in a cross section of the heart is by showing short line segments originating from the cross section and aligned with the local direction of the fibres. If the line segments are placed dense enough, one can see how the fibre orientations change. However, generation of the line segments takes time and thus the user has to wait for new geometry to be generated when the plane defining the cross section is changed. We present a new direct rendering method for the visualization of the 3D vector field in a 2D user‐definable cross section of a heart. On the intersection of the plane with the vector field, the full 3D vectors are rendered as 3D line segments with a local ray casting approach. No preprocessing of the data is needed and no geometry is generated. This technique allows a fast inspection of the data to identify interesting areas where further analysis is necessary (e.g. quantification or generation of streamlines). We also show how the technique is generalized to other glyph shapes than line segments by implementing ellipsoids.     

Wavelet-Based 3D Compression Scheme for Interactive Visualization of Very Large Volume Data

Interactive visualization of very large volume data has been recognized as a task requiring great effort in a variety of science and engineering fields. In particular, such data usually places considerable demands on run-time memory space. In this paper, we present an effective 3D compression scheme for interactive visualization of very large volume data, that exploits the power of wavelet theory. In designing our method, we have compromised between two important factors: high compression ratio and fast run-time random access ability. Our experimental results on the Visual Human data sets show that our method achieves fairly good compression ratios. In addition, it minimizes the overhead caused during run-time reconstruction of voxel values. This 3D compression scheme will be useful in developing many interactive visualization systems for huge volume data, especially when they are based on personal computers or workstations with limited memory.