Complex fenestration systems, such as prismatic and laser cut panels, are emerging as attractive options in architectural design thanks to their high potential to assist in energy and comfort issues. These systems can be used to redirect intense illumination from the sun but have complex transmissive properties that in turn depend on continuously changing illumination conditions due to the dynamic nature of natural light. The resulting non-intuitive interactions with the built environment make it necessary to develop tools that adequately represent these systems' behavior to the architect. The method presented in this paper enables simulation of the direct and indirect illumination from the sun and sky throughout each day for different months Preprint submitted to Automation in Construction 17 December 2007 of the year. The user can interactively explore the high-dimensional configuration space to select optimal materials early in the design process, using both qualitative and quantitative design criteria to make adjustments. (C) 2008 Elsevier B.V. All rights reserved.