Fast and accurate simulation of long-term daylight availability using the radiosity method

Studies have shown that long-term (e.g., annual or seasonal) predictions of daylight availability which do not take into account the luminance distribution of the sky for each single time-step show considerable differences from long-xterm predictions based on time and direction-dependent luminance distributions. However, with contemporary lighting simulation tools the latter can easily require computation times in the order of days. This paper presents two computation techniques that can be incorporated into any radiosity algorithm and that result in a reduction of computation times to the order of seconds for long-term simulations.