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A comparison of our Wide Spectral Range Sky Radiance Model with the original Prague Sky Model

A Wide Spectral Range Sky Radiance Model

Petr Vévoda Thomas Bashford-Rogers Monika Kolářová Alexander Wilkie

Abstract

Pre-computed models of sky radiance are a tool to rapidly determine incident solar irradiance in applications as diverse as movie VFX, lighting simulation for architecture, experimental biology, and flight simulators. Several such models exist, but most provide data only for the visible range and, in some cases, for the near-UV. But for accurate simulations of photovoltaic plant yield and the thermal properties of buildings, a pre-computed reference sky model which covers the entire spectral range of terrestrial solar irradiance is needed: and this range is considerably larger than what extant models provide. We deliver this, and for a ground-based observer provide the three components of sky dome radiance, atmospheric transmittance, and polarisation. We also discuss the additional aspects that need to be taken into consideration when including the near-infrared in such a model. Additionally, we provide a simple standalone C++ implementation as well as an implementation with a GUI.

Source Code Download

We provide a standalone C++ 17 implementation of the proposed sky radiance model. It contains the model library together with a simple example renderer and a GUI frontend to illustrate how to use the library:

Implementation source code

The range of atmospheric configurations that the model can render depends on the supplied dataset. Here is a version of the dataset presented in this paper, i.e. ground level with the extended range of wavelengths including the near-infrared:

Google Drive with the near-infrared dataset

Note that the implementation is compatible with all datasets previously released for the Prague Sky Model.

There is also a Python implementation created by Evripidis Gkanias from the University of Edinburgh. It comes in two versions: with GUI and lightweight without GUI.

BibTex Citation