A practical analytic model for daylight

TLDR

Sunlight and skylight are rarely rendered correctly in computer graphics due to high computational expense and the scarcity of precise atmospheric data. The authors aim to provide inexpensive analytic models that approximate full‑spectrum daylight and atmospheric effects while maximizing accuracy without compromising usability. The models use parameterized atmospheric conditions that users can measure or estimate to approximate full‑spectrum daylight and aerial perspective. The models were tested under various conditions and their intermediate results matched standard atmospheric science literature.

Abstract

Sunlight and skylight are rarely rendered correctly in computer graphics. A major reason for this is high computational expense. Another is that precise atmospheric data is rarely available. We present an inexpensive analytic model that approximates full spectrum daylight for various atmospheric conditions. These conditions are parameterized using terms that users can either measure or estimate. We also present an inexpensive analytic model that approximates the effects of atmosphere (aerial perspective). These models are fielded in a number of conditions and intermediate results verified against standard literature from atmospheric science. Our goal is to achieve as much accuracy as possible without sacrificing usability.