KDTree的经典实现以及相应的搜索过程，多种类共同实现。-Classic KDTree and the corresponding implementation of the search process, many kinds of common implementation.

KD-Tree 介绍教程，关于kdtree的原理，邻域。对三位点云配准很有帮助。-KD-Tree introductory tutorial on the principle kdtree of the neighborhood. For three-point cloud registration is helpful.