This paper focuses on the evaluation of a new model of radiation transfer in heterogeneous threedimensional media

based on the Monte Carlo ray tracing technique. This model is conceived as a virtual laboratory

where the targets can be individually characterized

and where the interactions between the radiation field and these targets can be explicitly controlled. The model can be used to generate reflectances as well as absorption profiles for arbitrarily complex threedimensional targets

such as an individual plant leaf or a complete forest canopy. The model performance is evaluated by comparing model simulations with laboratory measurements obtained over an artificial target. Observations have been carried out by the Advanced Techniques unit of the Space Applications Institute in the European goniometer （EGO） facility. Comparisons with laboratory measurements demonstrate the capability of our model to reproduce the actual observed reflectance factors of a fully documented target

and even to characterize the performance of this laboratory.