High redshift sources suffer from magnification or demagnification due to weak gravitational lensing by large scale structure .
One consequence of this is that the distance-redshift relation , in wide use for cosmological tests , suffers lensing-induced scatter which can be quantified by the magnification probability distribution .
Predicting this distribution generally requires a method for ray-tracing through cosmological N-body simulations .
However , standard methods tend to apply the multiple thin-lens approximation .
In an effort to quantify the accuracy of these methods , we develop an innovative code that performs ray-tracing without the use of this approximation .
The efficiency and accuracy of this computationally challenging approach can be improved by careful choices of numerical parameters ; therefore , the results are analysed for the behaviour of the ray-tracing code in the vicinity of Schwarzschild and Navarro-Frenk-White lenses .
Preliminary comparisons are drawn with the multiple lens-plane ray-bundle method in the context of cosmological mass distributions for a source redshift of z _ { s } = 0.5 .