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题名:
三维数据场体绘制中几类问题的研究与实现
作者: 孙文武
答辩日期: 2001
专业: 计算机应用技术
授予单位: 中国科学院软件研究所
授予地点: 中国科学院软件研究所
学位: 博士
关键词: 可视化 ; 体绘制 ; 体序 ; 图序 ; 裁剪 ; 遮挡 ; 立体绘制 ; 组合 ; 数据结构 ; 驾驭
摘要: 二维数据场是可视化技术处理的主要对象,而体绘制方法又是可视化中应用最广泛的一类技术。但是体绘制方法通常存在成象速度较慢、交互操作不灵敏活的缺点。为此,本文通过对人们识识数据场这一过程的分析以及研究数据场成象中具有的一些特点,提出了一些新的思想,以提高人们利用体绘制技术认识数据场的效率。现将作者在这方面所做的研究工作及取得的研究成果概括如下:1)在以物体空间为序的非规则数据场体绘制过程中,直接将那些投影完全位于图像不透明区域内的数据单元裁剪掉,可以减少需处理的数据量,加速绘制过程,且不影响图像质量。为此,本文通过建立一个与不透明度缓冲区同样大小的平均不透明度缓冲区,使得新方法只需对每一数据单元重心点在平均不透明度缓冲区内的值进行判定,就可得到此数据单元的可见性。其中平均不透明度缓冲区内每一个象素点的值,为不透明度缓冲区中相应点,在其周围一包含单元投影的区域内的平均不透明度值。而此区域大小可在预处理阶段得到。2)立体视图借助深度信息,能增强人们对复杂结构的认识程度。但是生成立体图却需要花费较长的绘制时间。为此,本文在采用基于一组平行切割平面的体绘制方法生成左视图的过程中[Yage96],通过将连续若干层切割平面上的中间采样图像先进行合成,将合成后的结果再投影到右图像平面上,从而减少右视图生成过程中对图像合成的计算量,提高立体绘制效率。3)对各种物质进行多种方式的组合成象,以了解它们各自的情况以及相互之间的关系,是认识数据场的有效途径。本文提出一种新的数据组织和表达结构,以方便组合要视化的实现。该方法通过为每类数据建立其空间分布信息的索引组织结构,使得进行可视化时,绘制方法只需选择所需处理的数据内容,从而避免对其它内容数据的计算。此外,由于该方法中每类内容是按照其空间分布有序组织的,因此所处理的各类内容数据之间的前后位置关系也易得到,保证了绘制效率。4)应用驾驭式可视化方法可以克服对整个数据场进行可视化具有的不足之处。本文通过在驾驭过程中抽取物质分界面,采取投影成象的体绘制方法,加快绘制过程。另外,该方法还提供局部操作的机制,以便对感兴趣局部特征进行细致研究。
英文摘要: Visualization for three-dimensional data fields is commonly used in many applications where volume rendering is widely applied. However, volume rendering is inherently time-consuming. In this paper, by investigating the process in which researchers study data field, we propose some new methods to improve the efficiency of studying data field through volume rendering. The research works conducted in this paper are summarized as follows: 1) In object-order volume rendering for irregular data fields, the cells occluded can be culled directly so as to reduce the amount of data and accelerate the rendering. In this paper, we use an average opacity buffer by convolving the opacity buffer with a box filter of the size which is calculated in preprocessing, each pixel in this average opacity buffer represents the average opacity of all pixels within a neighborhood of the dimensions of the projection bounding box with the size of box filter. Thus, the average opacity buffer enables us to determinate if a cell is fully occluded, accordingly culled, or if partially occluded, accordingly projected. 2) Stereoscopic images can help researchers comprehend complex data fields by employing depth information. But it would take a long time to render stereoscopic images. In this paper, by projecting onto right image plane the intermediate images composited from the images on successive slicing planes, while rendering the left image based on a series of parallel slicing planes [Yage96], the computation of composition in rendering the right image can be reduced, and the efficiency of stereoscopic rendering can be improved. 3) It is an effective way to study interesting contents by combining and rendering various contents so as to comprehend them and their relations with each other. In this paper, a new data structure is proposed to allow an efficient combinative volume rendering conveniently performed. By creating indexed data structures for each content, only interesting contents are rendered so as to prevent the computation for the uninteresting parts. In addition, the cells of each content are handled in order to make it easy to queue up the cells of the interesting contents. 4) Volume navigation can overcome the drawbacks of excessive computation for full data rendering. In this paper, projection method is taken to render images based on surface extracted on the fly, so the rendering is accelerated. Meanwhile, local operations are supported on data to optimize visualization of local features.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.iscas.ac.cn/handle/311060/7236
Appears in Collections:中科院软件所

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Recommended Citation:
孙文武. 三维数据场体绘制中几类问题的研究与实现[D]. 中国科学院软件研究所. 中国科学院软件研究所. 2001-01-01.
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