Abstract:Based on Snell law and Fermat principle,th,e two-point ray-tracing method for three dimensional arbitrary interface is studied in this paper.First,by use of one-order Taylor incomplete expansion,a positive definite matrix two by two,which is suitable to calculate reflection or refraction point in three-dimensional constructs,is obtained.Then,starting from an arbitrary given initial ray path,ray-tracing is iteratively calculated segment by segment.The procedure is kept on until the sum of adjustment quantity in the whole path is in the range of precision and the last iterative result is regarded as final three dimensional ray path.Now,the iterative ray-tracing segment by segment in three dimensional construct is finished.Numerical tests show that this algorithm is fast and its calculating precision can reach any requirements needed.