Zotti,G., Wilkie,A., Purgathofer,W.
Abstract:
The Preetham skylight model is currently one of the most widely used analytical models of skylight luminance in computer graphics. Despite its widespread use, very little work has been carried out to verify the results generated by the model, both in terms of the luminance patterns it generates, and in terms of numerical reliability and stability. We implemented the model in Mathematica, visualise and discuss those parameter ranges which exhibit problematic behaviour, and compare the computed luminance values with references from literature, especially the 15 standard skylight distributions published by the CIE. We also performed luminance measurements on real cloudless skies, and compare these measurements to the predictions of the model.