Monte Carlo Simulation of Infrared Radiation Through 3D Clouds

With the advent of modern GPU’s, it has become increasingly practical to simulatelarge numbers of photons for Monte Carlo-based radiance transfer. In this thesis, we ex-plore this topic for the purpose of simulating interactions between infrared light and cloudsusing the volumetric radiance transfer equation and Mie theory to accurately compute scat-tering probabilities and angles for homogeneous media. We create a path tracer which wevalidate against real world measurements of clouds and look at different important param-eters for modeling said clouds. We compare the more expensive but accurate Mie phasefunction to the widely used approximative Henyey Greenstein (HG) phase function. Wefind that HG only performs up to 3.5% faster while failing to accurately approximate theMie function. Finally, we derive a formula for precomputing radiance values of a cloud,including contributions of multiple scattering, for use in a simpler path tracer that doesn’tsupport multiple scattering. We test this formula and find that the resulting renders appearvisually reasonable.