  Sky illumination is a core source of lighting in rendering, and a substantial
amount of work has been developed to simulate lighting from clear skies.
However, in reality, clouds substantially alter the appearance of the sky and
subsequently change the scene's illumination. While there have been recent
advances in developing sky models which include clouds, these all neglect cloud
movement which is a crucial component of cloudy sky appearance. In any sort of
video or interactive environment, it can be expected that clouds will move,
sometimes quite substantially in a short period of time. Our work proposes a
solution to this which enables whole-sky dynamic cloud synthesis for the first
time. We achieve this by proposing a multi-timescale sky appearance model which
learns to predict the sky illumination over various timescales, and can be used
to add dynamism to previous static, cloudy sky lighting approaches.
