Building occupants are very sensitive to the levels, distribution and dynamics of artificial and natural. Simulation of the behaviour of light in buildings can be important to architects and engineers. Lighting simulation (of both natural and artificial light) can be used to give both qualitative impressions of building spaces and, more importantly, quantitative data that can be used to evaluate the buildings response to solar irradiation. Modern lighting simulation methods are capable of capturing the effect of complex reflections of light from multiple natural and artificial sources as well as the effects of ambient light. Lighting simulation methods can be used to capture representative conditions at a particular moment, under artificial sky conditions and annual solar energy distributions in and around a building.