Abstract: Participating media with an inhomogeneous index of refraction make light follow curved paths. Simulating this in a global illumination environment has usually been neglected due to the complexity of the calculations involved, sacrificing accurate physical simulations for efficient visual results.

This paper aims to simulate non-linear media in a more reasonable time than previous works without losing physical correctness. Accuracy is achieved by solving the Eikonal equation of geometrical optics, which describes the path followed by a light beam that traverses a non-linear medium. This equation is used in the context of a photon mapping extension.

To improve the efficiency of the method, we study the existing correlation between numerical methods and the description of the non-linear medium, in terms of simulation time and error. Also, by taking advantage of several features of the scenes that include non-linear media, new optimization techniques that can be applied both for ray tracing and photon mapping will be developed. Flight or driving simulators could greatly benefit from this work.