"Sand Field" a my little simple code. There you find ani - the button randomizly moving on 8 ways and length of she s current path. Around ani is sand field , ani can t move from sand field because one of the field parameter (temperature or pressure)

本例以由拓扑关系的arc/info 文件为数据源。其中a1,b1,c1是以fnode排序生成的数组，a1对应fnode,b1对应tnode,c1对应length,同样a2,b2,c2,是以tnode 生成的数组。Indexa1是对应某一起点与其相连的终点的个数，indexb1时对应某一终点与其相连的起点的个数，即其拓扑关系-length, the same a2, b2, c2, is based on an array of tnode generated. Indexa1 is a star