Ray tracing in absorbing media

In ray tracing, it is standard practice to consider solely the real part of any medium's refractive index for determining the changes in a ray's direction at the interface between two media. Any absorption is accounted for by reducing the intensity or weight of the ray in accordance with its propagation distance. This practice is adequate at optical wavelengths where absorption is generally very low but in the infrared and other regimes absorption can be significant and refraction angles and reflectances can deviate substantially from lossless cases. We calculate the quantitative consequence of a more rigorous approach to ray tracing for a lossy wedge and explore the potential differences in results from a Monte Carlo simulation of reflection from a rough, lossy surface. Comparisons between the traditional and complex ray tracing approaches are made and show that there can be significant discrepancies. (c) 2005 Elsevier Ltd. All rights reserved.