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Predicting Sky Dome Appearance on Earth-like Extrasolar Worlds

Alexander Wilkie Lukáš Hošek

Abstract

In this paper, we present a case study on how, given some rea- sonable assumptions, a sky dome model originally developed for terrestrial Predictive Rendering purposes can be re-used to give a scientifically plausible first impression of what outdoor scenes on earth-like exoplanets with a similar atmospheric structure would look like. On this very specific type of exoplanet, humans could reasonably be expected to survive without a space suit, and life-forms very similar to those found on Earth could theoretically evolve. This makes a simulation of typical outdoor lighting on this kind of planet interesting for various scientific (speculative exo-biological simulations) and not so scientific (”realistic” science fiction movie settings) reasons. If the properties of the exoplanet itself are restricted to resemble Earth, the remaining free parameter are the sun(s) which the exo- planet orbits. In the course of our case study, we found that even for fairly different star types, the overall appearance of the sky does not change as much as one might assume at first. Also, even the skies of Earth-like worlds that orbit binary stars would have a fairly normal appearance, although specific oddities can be observed.

Note: to access the paper PDF and the model source code, please use the “Source Code” link on your right. This leads you to the old sky dome modelling project page of our group, where these are provided (at the top, and there are two other publications presented on that page). Lots of people have links to the old page, so we are leaving this as it is.

Please also note that our 2021 SIGGRAPH paper on sky dome modelling provides a much improved sky model that is also available for download! Unless compatibility with old codebases is essential, the new model should be used whenever possible! The new model does not offer the “alien world” functionality out of the box yet, but if one looks at the relevant code in the old model, this is not hard to implement. Essentially, all that is needed is the same sort of spectral re-balancing as in the old model, which can trivially also be done with the new one.

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