矩形网格三点Fermat射线追踪技术

矩形网格三点Fermat射线追踪法是基于矩形网格三点扰动法的一种提高计算速度的方法．取矩形网格三个点，在Fermat最小旅行时原则下求取扰动中间点的位置，而不象扰动法那样依次扰动．因此，计算速度比扰动法提高2倍多，同时不受扰动摄动量大小选择的困扰．该方法继承了矩形网格三点扰动法的优点，对任意离散的速度场，总能找到最短时间路径，避免了射线盲区和追踪路径并非时间最短路径问题．

Three points Fermat ray tracing technique

The three points Fermat ray tracing is a new way for improvement calculated speed based on the three points disturbing in rectangle cell. The mid point position is determined under Fermat's principle from acquired the three points in rectangle cell rather than disturbing in turn like the three points disturbing method. Therefore, the computed speed of three points Fermat ray tracing is over 2 times more faster than the three points disturbing and it prevents the trouble from choicing quantity of disturbing. This method inherits the virtue from the disturbing way and always find the minimum raypaths for any discrete velocity fields, avoiding from shadow zone of ray tracing and non traveltime minimum raypaths.