【作者】 贾艾晨；

【导师】 韩国城； 魏小鹏；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2003， 博士

【摘要】 尽管近年来对可视化的研究已有了很大的突破，但可视化的方法中还有许多问题有待于人们去解决，比如如何提高体绘制速度、如何动态地显示数据场可视化图像等，这些问题的解决，会进一步扩大可视化的应用领域和范畴。在大坝地震反应分析中，所常用的后处理软件的可视化功能主要是二维显示，三维的可视化功能非常有限，只能显示表面的应力分布和位移变化，无法显示大坝内部场值分布的变化过程，没有达到理想的可视化效果。 本文充分考虑了大坝地震反应数据场的特点，以大坝地震反应数据场的可视化方法研究为主要内容，以研制开发大坝地震反应可视化系统为最终目的，提出了几种可行性强的数据场可视化方法。其具体研究内容如下： (1)、基于St.Andrew单元剖分的基本思想，对定义在四节点非正规化网格上的地震反应数据进行等值线抽取，并以多种颜色绘制出计曲线。采用扫描线方法，计算出断面上像素点的场值及对应的颜色值，绘制出颜色连续变化的场值云图，使人们清楚地了解大坝地震反应中指定断面的场值分布。 (2)、为了使人们了解大坝地震反应整体应力分布情况，提出多层断面云图显示方法，将大坝多层断面的场值云图通过轴测投影变换后显示在一个画面里，并使其光强叠加，透过前一个断面可看到后一个断面的场值分布。该方法既能显示大坝单个断面的应力分布，又能观察和比较大坝各个断面的应力情况，生成方法简单，易于推广，为体数据的三维可视提供了简单可行的途径。 (3)、为了弥补传统体绘制静止画面不能明确判断场值集中部位的不足，提出一种快速体绘制算法，针对大坝地震反应有限元计算数据场，根据每个单元法线与视线夹角最小的表面来选择剖切方向，将单元剖切成多个四边形面后，对单元的绘制顺序进行合理排序，利用OpenGL图形库函数进行颜色融合，再将各个单元依次叠加，从而生成了三维数据场的体绘制图。该方法大大提高了体绘制速度，实现了从不同视点动态观察体绘制图，可以清楚地分析场值集中部位。 (4)、为了动态地显示大坝地震反应数据场的整体变化情况，本文提出了基于网格、表面、体绘制和多断面的数据场三维动态可视方法，并给出了位移数据场的几种动态可视方法，可以立体地反映出三维数据场的整体数据分布，实现大规模数据场实时动态可视，使人们及时准确地了解大坝地震反应过程，正确地做出决策。 (5)、举例说明了分形的IFS方法；推导出Koch曲线的具体迭代算式；给出了由分形插值曲面生成地形图的具体方法;提出了在同一递归深度取相同随机量的方法解决中点变位法中的裂缝问题，实现了用三角形中点变位法和四边形中点变位法绘制场景中的山形，从而用连续四边形面片构造出了库区山形及河道，用分形曲面构造出了河床，逼真地全景显示了可视化场景。 可视化是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的交叉学科，可视化在土木工程中的应用又会涉及到土木工程中的许多实际工程问题，因此要达到完善大坝地震反应可视化方法及研制开发大坝地震反应可视化系统的目标，还有大量艰苦的工作要做。更多还原

【Abstract】 The study on Scientific Visualization has great achievement recent years, but there are many questions in methods of Visualization which are waiting to be solved, such as how to enhance the speed of volume rendering, how to show the data field visualization images dynamically. Solving these questions will extend the application fields of Visualization. In analysis of dam seismic response, the main visualization function of post treatment software mostly used is 2D display. The 3D visualization function is very limited, which only show the surface stress distribution and surface displacement changes, can not show the changing process of field value distribution inside dam, and not reach the satisfactory level of visualization.This dissertation fully considers the special feature of dam seismic response data, the study of visualization method for dam seismic response data is as this paper’s main content, research and development of dam seismic response visualization system is as this paper’s last aim, this paper presents several feasible methods of data visualization. The main contents studied in this dissertation may be summarized as follows:(1) Based on the basis thought of St.Andrew in finite element subdivision, draws off contours in dam seismic response data which is defined on four-node irregular nets, and draws out the integer curves by colors. Using scanning line method, calculates the field value of image element on dam section and relative color value, draws out the color contour which colors change continually. The section field value distribution of dam seismic response can be seen clearly.(2) Presents a visualization method-multiple section color contour display, whichcan not only display the stress diagram of single dam section, but also make the stress diagram on several dam section be showed and be compare. This method is a simple and efficient method of volume data visualization.(3) The concentrative part of field value can’t be judged exactly on the static picture of classical volume rendering. In order to remedy this kind of shortage, this paper presents a quick volume rendering method, for the finite element data field of dam seismic response, choices the slicing direction relying on the element surface which normal line has the smallest included angle with the view direction, slices elements to many quadrilaterals, blends the colors of these quadrilaterals by using OpenGL blending technology, and thensuperimposes all elements one by one. This method accelerates the speed of volume rendering, thus, we can observe dynamic pictures of volume rendering and analyzes the concentrative part of field value clearly.(4) The data of dam seismic response is changeable by time. In order to visualize this kind of data, this paper presents several 3D dynamic visualizing methods based on neU surface, volume rendering and multiple-section. By these methods, the field value’s distribution of whole dam can be showed clearly, dynamic rendering for large volume data can be achieved, people can understand the process of dam seismic response promptly and exactly and make correct decision.(5) Explains the fractal IPS method by example, deduces the actual iterative formulas, gives the method of generating terrain map by fractal interpolating surface, presents a method of getting same random parameter at the same depth of recursion, which method can solve the cleft in midpoint deflection method. Draws out mountain shape of visualization scene by triangle midpoint deflection method and quadrilateral midpoint deflection method. Then constructs the mountain shape and stream channel of reservoir field by continuous quadrilateral chips, and constructs channel bed by fractal surface, shows the whole visualizing scene truly.Visualization is a interdiscipline which relates to Computer Graphics, Image Processing, Computer Aided Design, Computer Visual Sense, People and Computer Interactive Technology, etc. The application of visualization in civil engineering also touches many real engineering prob更多还原