八叉树（Octree）的定义是：若不为空树的话，树中任一节点的子节点恰好只会有八个，或零个，也就是子节点不会有0与8以外的数目。-Definition octree (Octree) is: If the tree is empty, then any tree node s children will have exactly eight, or zero, that is, the number of child nodes 0 and 8 will not have outside.