数据可视化技术及其应用

数据可视化技术及其应用

摘要:数据可视化是计算机学科的一个重要研究方向。文中简要介绍了数据可视化所需的技术:数据预处理、映射、显示以及可视化技术在医学、气象预报、工程及数据挖掘中的应用。

关键词: 数据可视化; 计算机图形学

Datavisualizationanditsapplications

Abstract:Datavisualizationisanimportantresearchareaincomputerscience.Inthispape r,datavisualizationtechnologiesincludingdatapre2treatment,mappinganddisplayinga rebrieflyintroduced,anditsapplicationsinmedicine,weatherforecasting,engineering anddataminingarepresentedalso.

Keywords: Datavisualization; Computergraphics

1 引言

随着科学技术的不断发展,大量的由计算机产生的中间数据都需要进行可视化处理,以求达到辅助分析、再现客观的目的。现代的数据可视化[1]技术指的是运用计算机图形学和图像处理技术,将数据换为图形或图像在屏幕上显示出来,并进行交互处理的理论、方法和技术。它涉及到计算机图形学、图像处理、计算机辅助设计、计算机视觉及人机交互技术等多个领域。换句话说,可视化技术是一种计算方法。它将符号描述转变成几何描述,从而使研究者能够观察到所期望的仿真和计算结果。此外可视化技术提供了将不可见转化为可见的方法。它丰富了科学发现的过程,促进对未知事物的领悟。近年来,可视化的应用范围随着计算机技术、图形学技术的发展而不断拓宽,除了继续在传统的医学、航空学、汽车设计、气象预报和海洋学领域的深入研究外,近年来,随着互联网络技术和电子商务的发展,信息可视化已经成为可视化技术的热点研究内容。应用可视化技术,可以在具有大量高维信息的金融、通信和商业领域中发现各自数据中所隐含的内在规律,从而为决策提供依据。事实上,可视化技术已经成为许多领域必不可少的计算机辅助后置数据处理部分

1 Introduction

With the development of science and technology, computer generated large amounts of intermediate data are required for visual processing, in order to achieve the computer-aided analysis, reproduction of the objective purpose. Data visualization of modern [1] technology refers to the use of computer graphics and image processing technology, the data into the graphics or images displayed on the screen, and the theory, method and technology of interactive processing. It involves many fields of computer graphics, image processing, computer aided design, computer vision and human-computer interaction technology. In other words, the visualization technology is a kind of calculation method. It will be the symbol description into a geometric description, simulation and calculation results so that researchers can observe the desired. In addition, visualization technology provides the invisible into the visible method. It is rich in the process of scientific research, promotion of the unknown. In recent years, the scope of application of visualization of expanding with the development of computer technology, computer graphics technology, besides the further study in traditional medicine, aviation, automobile design, meteorological and oceanographic field, in recent years, with the development of

Internet technology and e-commerce, information visualization has become a hotspot of research contents of visualization technology the. The application of visualization technology, can find the inherent rules implied in their data in which a large number of high dimensional information of financial, communications and business fields, so as to provide the basis for decision making. In fact, the visualization technology has become essential to many applications of computer aided data post processing part of the

2 数据可视化技术

用于创建和操作的可视化技术由数据集合生成的图形描述。有些可视化技术是针对某些特别的应用开发的,而另一些技术具有普遍的适用性。这一部分主要针对通用的可视化技术。此外,可视化技术涵盖范围较广,这里只将可视化技术按一般可视化所必需的过程划分为“数据预处理”、“映射”、“绘制”和“显示”四步。

2 data visualization technology

Used in the visualization technology to create and manipulate described by the data set generated graph. Some visualization technology is developed for some special application, and some other techniques have general applicability. This part mainly aimed at the visualization technology of general. In addition, the visualization technology covers a wide range, here only the visualization technology is necessary according to the visualization process into "data processing", "map", "drawing" and "show" the four step.

2.1 数据预处理

可视化模块输入来自计算机的模拟数据和实验/测量数据,此外还包括数据库中数据的调用。可视化处理的对象包括“符号”、“结构”、“图像”与“信号”。原始的符号、结构、图像与信号等对象的生成与获取是从事科学与工程计算和实验的科学家或工程师的任务。如何将这些数据变换成可视的图形(图像)信息,则是从事科学计算可视化应用的科学家和工程师的任务。他们与从事基础研究或工程研究的科学家们相结合,运用可视化工具,实现并完成将不可见的对象变换成可见图像的过程。通常对这些原始数据的处理应包括以下两个方面:

(1) 原始数据预处理及存储

通常用于可视化的原始数据预处理部分要涉及到以下的操作:

1)数据格式及其标准化;

2)数据变换技术;

3) 数据压缩和解压缩。

1)经过上述处理的数据可能会具有较大的数据容量。通常要采用标准化的数据交换格式存储。美国国家超级计算中心的NASA等单位研究提出的科学数据存储和交换格式/结构,如HDF、CDF和NetCDF等。这些数据格式通常具有自描述的特性,易于存储和读取,被广泛用于海洋、气象环境模式计算以及大规模数值计算等方面。

2)(2) 面向可视化方法的数据处理

针对不同的可视化方法和内容,需要对原始数据做进一步的变换处理,以满足可视化要求。例如,对于医学图像的三维重建,就需要对原始CT图像序列进行三维的滤波、重采样、三维图像分割与边缘检测等预处理。对原始数据进行变换处理的操作主要包括:

1) 数据规范化处理;

2) 滤波处理;3) 平滑处理;4) 网格重新划分;5) 坐标变换;6) 几何变换;7) 线性变换;8) 分割与边缘检测;9) 特征检测、增强和提取;10) 查色表操纵和特征映射等等。

2.1 data preprocessing

The visualization module input simulation data and experimental / from computer measurement data, in addition to the data in the database call. Visual processing of objects including "symbol", "structure", "image" and "signal". With the acquisition of the original symbol, structure, image and signal of the object is engaged in scientific and engineering calculation and experimental scientist or engineer task. How these data will be transformed into visual graphic (image) information, is engaged in the visualization application scientists and engineers the task of science. They are combined with the scientists engaged in basic research or engineering, using visualization tools, implementation and completion will not visible object is transformed into a visible image process. Common to these original data processing should include the following two aspects:

(1) the data processing and storage

Usually used for the pre-processing of the original data part visualization involves the following operations:

1) data format and its standardization;

Data transformation technology;

3) data compression and decompression.

After the above processing data may has a large data capacity. Usually use a standard data exchange format. Scientific data storage USA National Supercomputing Center in NASA unit of and exchange format / structure, such as HDF, CDF and NetCDF etc.. These data format is usually has the characteristics of self description, easy to store and read, is widely used in marine, meteorological computing environment model and large-scale numerical calculations.

(2) for the visualization of data processing

The visualization methods and content of different, need to transform a further treatment of the original data, to meet the visual requirements. For example, for the 3D reconstruction of medical image, need, resampling, 3D image segmentation and edge detection preprocessing of 3D filtering of the original CT image sequence. Transform the operation of the original data mainly includes:

1) standardized data processing;

2) filtering; smoothing; 3) 4) 5) re meshing; coordinate transformation; geometric transformation; 6) 7) linear transform; 8) segmentation and edge detection; 9) feature detection, enhancement and extraction; 10) color look-up table manipulation and feature mapping etc..

2.2 映射

映射模块是完成将数值数据转变成几何数据的功能,因此映射功能实质上完成的是数据建模功能,是可视化技术的核心。可视化处理的数据类型随着应用领域的不同而不同,因此对不同类型的应用数据应采用不同的映射技术。一些常见的方法如:

(1)应用图形中可识别的变量来验证维数的基数。

(2)使用缩放比例和偏移量匹配数值范围。(3)使用衍生值(残差、logs)来强调变化。(4)使用投影来压缩信息、获得统计量。(5)使用随机抖动来区分重叠。

(6)使用多视图来处理隐藏关系高维信息。(7)使用有效的网格关键字或标签来帮助理解

2.2 mapping

Mapping module is to complete the numerical data into geometric data, so the mapping function is essentially complete data modeling capabilities, is the core of visualization technology. Visualization of data types with the application is different, so the application data of different types should adopt different mapping technique. Some common methods such as:

Variables can be identified using graphics to validate the dimension of the base.

(2) the matching numerical range using the scaling and offset. (3) using the derived value (residual, logs) to emphasize the changes. (4) using the projection to compress information, to obtain statistics. (5) using random jitter to distinguish overlapping.

(6) the use of multi view to deal with high dimensional information hidden relationships. (7) the use of effective mesh keywords or tags to help understand

2.3 绘制

绘制功能应完成将几何数据转换成图像的过程,计算机图形学中真实感成像包括两部分:物体的精确图形表示;场景中光照效果的适当物理描述。

物体的精确图形表示包括几何体建模技术、扫描转换技术、反走样技术、隐藏面消除技术。一个完整精确的图形描述通常需要综合应用这些技术,同时,还要考虑用户对图形表示的需要,不能把图形模型建得过于简单,也不能过于复杂。

光照效果包括光的反射、透明性、表面纹理和阴影。光照效果由描述物体表面各点光强的光照模型来表示,为可见物体建立光照效果模型是一个非常复杂的过程。大多数软件都采用由物体表面光强度的物理公式推导出来的简化光照模型。

2.3 drawing

Drawing function should complete the geometric data into image process, computer graphics, realistic image includes two parts: said accurate graphic object; describe the appropriate physical light effects of the scene.

Precision graphics object representations including geometry modeling technology, scan conversion, anti aliasing, hidden surface removal technology. A complete and

accurate description of the graphics usually requires the integrated application of these techniques, at the same time, but also consider the needs of users to graphically, not the graphics model is too simple, can not be too complex.

The light effect including the reflection of light, transparency, surface texture and shading. The light effect by describing an object points on the surface of the light intensity of illumination model to represent, established as a visible object illumination model is a very complex process. Most software used by the optical surface strength of the simplified formula derived physical illumination model.

2.4 显示

显示模块的功能是将绘制模块生成的图像数据,按用户指定的要求进行输出。显示模块类似于图形用户界面(GUI)技术,其对应的软件层提供各种设备的驱动程序。显示模块除了完成图像信息输出功能外,用户的反馈信息也是通过显示模块传送到其它软件层中,以实现人机交互。人机交互是可视化的一项重要指标,许多可视化要求实现动态调整映射关系,通过改变视图遍历数据,视图缩放等操作。

2.4 display

The display module is the function of image data will be rendering module, output according to user specified requirements. The display module is similar to the graphical user interface (GUI) technology, the corresponding software layer provides all kinds of driver equipment. Display module in addition to completing the image information output function, the user feedback information is through the display module to the other software layer, in order to achieve human-computer interaction. Human computer interaction is an important index for visualization, dynamic adjustment mapping requires a lot of visualization, by changing the view through a data, view zoom. The derived formulas simplified illumination model.

3 数据可视化的应用

3.1 医学

可视化技术已广泛应用于诊断医学、整形与假肢外科中的手术规划与辐射治疗规划等方面。在以上应用中核心技术是将过去看不见的人体器官能以二维图像形式显示出来或重建它们的三维模型。由于三维医学图像构模涉及的数据量大、体元构造算法复杂、运算量大,因此至今仍是医学图像可视化技术中的瓶颈所在。在这一领域中图像处理技术占主流,而计算机视觉与图形学则在整形外科的手术中起主要作用。

图1为脑部核磁共振图像序列重构的三维脑部图像。此类三维图像将有助于医生决定是否需要外科手术,应用何种方法和需要何种硬件工具的问题。目前在医学可视化领域主要包含三方面的研究热点:图像分割技术、实时渲染技术和多重数据集合的图像标定技术。这些技术的发展将进一步促进可视化技术在医学技术中的推广。3.2 气象预报

气象预报中涉及到大量的可视化内容,从普通的云图到中尺度数值预报。大量的气象观测数

据都必须经过可视化后再向用户提供信息。一方面,可视化可将大量的数据转换为图像,在屏幕上显示出某一时刻的等压面、等温面、漩涡、云层的位置及运动、暴雨区的位置及其强度、风力的大小及方向等,使预报人员能对未来的天气作出准确的分析和预测。另一方面,根据全球的气象监测数据和计算结果,可将不同时期全球的气温分布、气压分布、雨量分布及风力风向等以图像形式表示出来,从而对全球的气象情况及其变化趋势进行研究和预测。图2为三维空间里的风暴前锋模型。图中描述了冷暖锋面及锋面相交时的压力场分布。

Application of 3 data visualization

The 3.1 medicine

Operation planning and radiation treatment planning, visualization technology has been widely used in medical diagnosis, plastic and artificial limb surgery. The core technology in the above applications is the invisible human organs to two-dimensional image or display of 3D models and their. The 3D medical image modeling involves a large amount of data, body structure complexity, large amount of computation, so it is still medical image visualization technology bottleneck. In the field of image processing technology in the mainstream, and computer vision and graphics in the orthopaedic operation plays a major role in.

Figure 1 is a three-dimensional images of the brain magnetic resonance image sequence reconstruction. The three-dimensional image will help doctors decide whether to need surgical operation, and what methods and problems need what kind of hardware tools. At present in the medical research focus mainly includes three aspects: image segmentation image technology, real-time rendering technology and multiple data sets of calibration technology. The development of these technologies will further promote the visualization technology in medical technology. 3.2 weather forecast Related to the visual content of a lot of weather forecast, from ordinary images to mesoscale numerical weather prediction. Meteorological observation data must be approved by the visualization to provide information to the user. On the one hand, visualization can be a lot of data into image, showing the position of isobaric one time, isothermal surface, vortex, clouds and motion, rainfall area and intensity, the size of the wind and the direction on the screen, the forecaster to make analysis and prediction of future weather. On the other hand, according to the global weather monitoring data and calculation results, the different periods of global temperature distribution, pressure distribution, distribution of rainfall and the direction of the wind in the form of image representation, research and forecast the global weather situation and trend. Figure 2 is the storm striker model in three-dimensional space. Figure describes the cold front and the front intersection when the pressure field distribution.

3.3 工程

可视化在工程中有着广泛的应用,这里仅就其在计算流体力学中的应用为例进行说明。

计算流体力学(CFD)就是求解流体偏微分方程,即Navier2Stokes方程的数值解,这些方程式

是航空学、汽车设计、气象预报和海洋学等应用研究的核心,也是理解流体动力学的基础。计算流体力学领域的主要研究方向可分为科学计算(求解算法)与可视化(描述复杂矢量场技术)两部分,其主要目的是对流体

运动的仿真。随着超级计算机的应用,计算流体力学仿真的精度和复杂性提高很快,例如目前已可对复杂

几何形状的三维Navier2Stokes流进行仿真。

在流场计算的一般过程中,可视化技术起着十分重要的作用。首先,可视化技术提供交互设计手段以方便与加快物体的定义过程,研究人员可直观地校验物体各部分的几何尺寸大小、部件间是否留有缝隙、物体表面是否光滑等。其次,在对计算区域进行网格剖分时,可视化技术能把生成的网格显示出来,以便让研究人员检验并及时调整和伸缩网格线,使之形成合理的空间分布。最后,在计算和对计算结果的分析过程中,可视化技术的作用更大。它利用计算机图形学所提供的各种方法描述流场中的各种物理量的分

布情况,如压力、密度等标量和速度等矢量(如图3所示),并用不同颜色的等值线(面)或不同深浅的同种颜色填充网格来表示标量的数值差别,以带箭头的线段来描绘矢量的方向,对冲击波、涡流、驻点等各种流场结构,也可用计算机图形学提供的方法进行描绘。而且,可视化技术实时交互地变化画面大小并提供动态显示,以使分析者看清流场中各种现象的细节并作进一步分析。

3.3 Engineering

Visualization is widely used in engineering, here only for its application in computational fluid dynamics as an example.

Computational fluid dynamics (CFD) is the solution of fluid partial differential equation, namely the numerical solutions of the Navier2Stokes equation, the equation is the core application of Aeronautics, automotive design, meteorological and oceanography, but also the basis for the understanding of fluid dynamics. The main research direction of the field of computational fluid dynamics can be calculated into scientific (algorithm) and visual (describe the complex vector field) the two part, it is the main purpose of the fluid

Motion simulation. With the application of super computer, precision and complexity of computational fluid dynamics simulation to improve soon, for example, has the complex

Three dimensional geometry of Navier2Stokes flow simulation.

The general process flow calculation, visualization techniques play a very important role. First of all, the visualization technology to provide interactive design means to facilitate and accelerate the process of object definition, researchers can intuitively the check the geometry size, whether there is a gap between parts, the object surface is smooth. Secondly, in the region is divided into grid, visualization technology can make the mesh generation and display, in order to allow researchers to test and adjust and telescopic grid lines, to form a reasonable distribution of space. Finally, in the course of calculation and Analysis on the calculation results, the visualization technology has more influence on. It uses a variety of methods

of computer graphics provides a description of various physical quantities in the flow field of

Cloth, such as pressure, density and velocity scalar vector (as shown in Figure 3), and the contours of different colors (surface) or varying shades of the same color filling mesh to represent the difference between the scalar, vector direction to describe the by line with an arrow, the shock wave, vortex, the stagnation point various flow structure, method can also be used in computer graphics to provide to paint. Moreover, the visualization technology of real-time interactive change screen size and provides dynamic display, so that analysts see the various phenomena in the flow field details and further analysis

3.4 数据挖掘

数据挖掘中的可视化[3]是信息可视化中的重要部分。在数据挖掘中,可视化是一个多面手。它能使人在视觉上理解多维数据中的复杂模式。通过观察数据在多重维数和多重图形窗体中的存在形态,可以直观、迅速地揭示数据趋势和外露层。在数据挖掘过程中,数据挖掘也可以帮助在建模之前考察数据,可以验证其数据挖掘工具的结果。此外,可视化对局部数据的模式发现有着重要的作用。数据可视化的上述特性为数据挖掘在揭示金融、通信和商业领域内在规律方面提供了清晰的思路和直观的形象。

The 3.4 data mining

Visualization of [3] data mining is an important part in information visualization. In data mining, visualization is a generalist. It can make people understand complex multidimensional data model in the visual. Through the observation data in multiple dimensions and multiple graphics in the form of existence, can directly, rapidly reveal data trends and exposed layer. In the process of data mining, data mining can help the data before the modeling, can verify the tools of data mining results. In addition, plays an important role in discovery mode visualization of local data. The characteristics of data visualization in reveal the inherent law of financial, communications and business provides a clear thinking and intuitive image for data mining

参考文献:

[1] 唐泽圣.三维数据场可视化[M].北京:清华出版社,1999.[2] https://www.360docs.net/doc/ab13984387.html,rmationvisualization[J].IEEECom2

puterGraphicsandApplications,1997,17(4):29231.[3]

KeamDA.Visualizationtechniquesformininglargedatabas2

es:acomparision[J].IEEETransactiononKnowledgeandDataEngineering,1996,8(6).