利用高斯描绘子进行字符识别

高斯描绘子是一种基于边缘的形状特征，具有识别/匹配率高、相对于平移、旋转、尺度和反射不变、计算量小、对适度的边缘变动和噪声不敏感以及适用范围广等优点。将高斯描绘子用于字符识别，并与另一种基于边缘的特征轮廓矩不变量Hu矩的推广和改进进行比较。实验结果表明，高斯描绘子有很好的识别效果。     

Estimating subdivision depth of Catmull-Clark surfaces

In this paper, both general and exponential bounds of the distance between a uniform Catmull-Clark surface and its control polyhedron are derived. The exponential bound is independent of the process of subdivision and can be evaluated without recursive subdivision. Based on the exponential bound, we can predict the depth of subdivision within a user-specified error tolerance. This is quite useful and important for pre-computing the subdivision depth of subdivision surfaces in many engineering applications such as surface/surface intersection,mesh generation, numerical control machining and surface rendering.