Research on techniques for classifying and searching for large-scale volume datasets using critical point graphs

在这项研究中，我们开发了一种构建临界点图的技术，该临界点图可以用简单的几何表示体数据集，以便于分类和搜索。由计算机模拟和测量设备产生的数值数据集被称为体数据。2003年，我们开发了一种从标量体数据集构造临界点图的算法。当我们计算临界点图时，我们沿着临界点的特征向量的方向，从一个离临界点很近的点开始画一条矢量线。由于目前我们不知道多小的距离是足够的，我们对改变向量线的起始位置来改变临界点图的几何形状进行了敏感性分析。2004年，我们开发了一种使用体数据集的临界点图来计算体数据集之间的相似性度量的技术。首先，我们定义了临界点图的特征向量。特征向量由关于关键点及其连通性的信息组成。前者包括临界点的标识、点坐标、标量数据值、临界点的类型。后者包括圆弧的标识符、两端的临界点和沿圆弧的体积单元。我们假设临界点图形是一个用3D描述的字符，并发展了一种利用模式识别技术来计算临界点图形之间的相似度的技术。

In this research, we developed a technique of constructing a critical point graph which can represent a volume dataset using a simple geometry in order to facilitate classifying and searching. Hear, we call a numerical dataset which is generated from computer simulation and measurement device as a volume data.In 2003, we developed an algorithm for constructing a critical point graph from a scalar volume dataset. When we calculate a critical point graph, we trace a vector line from a point which is located a small distance away from a critical point in the direction of the eigen vector of the critical point. Since, currently, we do not have any knowledge about how small distance is adequate, we carried out a sensitivity analysis about how a geometry of the critical point graph changes by changing a starting location of the vector line.In 2004, we developed a technique of calculating a similarity measurement between volume datasets using their critical point graphs. First, we defined a feature vector of a critical point graph. The feature vector is composed of information on the critical points and their connectivity. The former includes identifiers of critical points, point coordinates, scalar data values, types of critical points.. The latter includes identifiers of arcs, critical points at the both ends, and volume cells along the arcs. We assumed a critical point graph as a character described in 3D and developed a technique of calculating a similarity between critical point graphs by using pattern recognition techniques.