Photorealistic rendering of scenes with physically-based sky light

Andreas Agvard

Lund University

Fredrik Lanker

Lund University
Supervisor: Tomas Akenine-Möller


This master thesis presents an application that creates images of skies that can be used to produce photorealistic renderings of outdoor scenes. These images are called light probes. The application is divided into two parts, a real time part and a part where an actual rendering of a light probe is done. In the real time part the user chooses a time and position on Earth whereafter an approximation of the sky with these parameters is visualized. These parameters can then be transferred into the second part where a high quality light probe of the sky is created. In the latter part, our approach is to make a physically correct rendering of the sky where both single and multiple scattering of the light due to particles in the atmosphere are taken into account. The scattering is computed by using well-established theories developed by Rayleigh and Mie. The image of the sky is saved as a high dynamic range light probe in the RGBE format created by Ward. This light probe can then be used as a light source when rendering three dimensional scenes in any renderer supporting light probes and high dynamic range images.

This thesis also showes examples of two postprocessors that can be applied to the rendered scene, a glare effect and tone mapping. The glare effect is used to simulate the phenomenon that can be seen as a hazy glow in the area closest to a bright light source. Tone mapping is used to present high dynamic range images on a monitor with a limited dynamic gamut.


Photorealistic rendering of scenes with physically-based sky light (pdf, 8.68 Mb)
Rendering the sky (pdf, 1.14 Mb)
Presentation (pdf, 685 Kb)


real time version
Approximation from real time version.
rendered version
The rendered version of the previous image.
A scene rendered with one of our light probes. Glare effect is also added.
dramatic sunset
A somewhat more dramatic sunset that is the result of changing some parameters.
planet weird
Example of a totally unrealistic sky that can be achieved by tweaking some parameters. A glare effect is also added.


Andreas Agvard: andreas at agvard dot se
Fredrik Lanker: fredrik at lanker dot se

Old page with some additional images.