Nested radiosity for plant canopies

We present nested radiosity, a new approach for simulating the distribution of natural light within plant canopies. The geometric description of a canopy requires many polygons, and its spatial coherence is lower than that of an architectural scene. We compute the total irradiance of polygons by summing the irradiance due to close polygons (calculated with the radiosity equation) and the irradiance brought by distant polygons (approximated by the radiative transfer equation). The reduced number of form factors can be stored in a sparse matrix. Then several radiative conditions can be quickly simulated. The simulation results for this model are compared with those produced by a Monte Carlo ray tracing.