RAYTRAN - A MONTE-CARLO RAY-TRACING MODEL TO COMPUTE LIGHT-SCATTERINGIN 3-DIMENSIONAL HETEROGENEOUS MEDIA

A model of radiation transfer in three-dimensional (3-D) heterogeneous media is designed and evaluated, This model implements state-of-the-a rt Monte Carlo ray-tracing techniques and is dedicated to the study of light propagation in terrestrial environments. It is designed as a vi rtual laboratory, where scenes of arbitrary complexity can be describe d explicitly and where the relevant radiative processes can be represe nted in great detail, at spatial scales relevant to simulate actual me asurements. The approach capitalizes on the existing understanding of the elementary radiative processes and recognizes that the major diffi culty in accurately describing the radiation field after its interacti on with a typical terrestrial scene results from the complexity of the structure and the diversity of the properties of the elements of the scene, The output of the model can be customized to address various sc ientific investigations, including the determination of absorption pro files or of light-scattering distributions. The performance of the mod el is evaluated through detailed comparisons with laboratory measureme nts of an artificial target as well as with other established reflecta nce models for plant canopies.