A radiosity approach for the simulation of daylight

In this paper, an extension to the radiosity method, for the simulation of daylight, is presented. The sky hemisphere around the scene is subdivided into a set of sky patches. By defining a location on the earth, a time of day and the weather conditions (e.g., clear sky, overcast, partly cloudy) a sky model (e.g., CIE or Perez) is applied to compute the radiosity values for each sky patch. In a radiosity preprocess, the sky patches are regarded as shooting patches and are treated first. By storing the form factors within this presprocess, all parameters of the sky model can be modified and updated very quickly. Thus, a designer can see the lighting variation throughout a typical day b calling the costly form factor computation only once.