Simulation de la diffusion de la lumière et des gaz par techniques de Monte Carlo. (Simulation of light and gaz diffusion with Monte Carlo technics)

Realistic image synthesis requieres an accurate modelling of the interactions of light with matter (reflection, refraction, scattering) and of luminous energy exchanges between the objects of the scene. This modelling, very complex if no restrictive assumption is made, can be efficiently fulfilled with a Monte Carlo simulation. In the present work, we define first of all a complete scene illumination method, based on a Monte Carlo simulation of a particule model of light. First, we develop this simulation for participating media. We lower the variance of the simulation by an exact computation of the absorption. Then, we extend this work to surface objects and we propose a grouping technic of photons in order to obtain a constant efficiency for each calculation step. In the second part of this work, we study the application of this method to the visualization of 3D scalar fields, then the application of some technics derived from image synthesis (polygonisation of volume data, spatial partitioning, distance images, ...) to the simulation of gaz diffusion which presents numerous similarities with the simulation of scattering of light.