Modelling the light environment of virtual crop canopies

Virtual plants describe functionally and geometrically plants as sets of interconnected organs. As many plant processes are driven by light, virtual plants require the estimation of the light absorbed by each organ. This has motivated the development of dedicated light models taking profit from the 3D geometry provided by virtual-plant models. We first introduce the principles governing the physical interactions between light and a plant canopy. We then review operational models, including fast methods that have been developed for calculating sun and sky light intercepted by plant organs. Such methods may be used for the simulation of processes depending on the UV or PAR radiations. Models taking into account the multiple scattering between plant elements are based either on Monte Carlo ray tracing or on the radiosity method. We present the principle of these approaches and recent developments in their applications to crop modelling.