Sky

A Practical Analytic Model for Daylight
by A. J. Preetham, Peter Shirley, Brian Smits

Entry created by Andreas Jung.

The paper presents a model to generate a daylight sky using analytic formulas. The results are convincing, and the costs are reasonable. The technique is limited to a daylight sky only. [IMO] The paper itself is not too hard to follow and the practical implementation can be considered doable. The computational costs are low enough to perform the sky calculations in the background. Unfortunately, the paper renders itself unusable for a wide range of application, because it does not support night skies.

Display of The Earth Taking into Account Atmospheric Scattering
by T. Nishita, T. Sirai, K. Tadamura, E. Nakamae

Entry created by Andreas Jung.

In case one cannot use an analytical sky model, one most likely has to choose a technique which generates the sky color by calculating scattering accross a given ray. This paper is virtually the first paper that presents this technique - it uses Rayleigh-Scattering and an approximation of Mie-Scattering. [IMO] Although there are many extensions to this technique available, this is the bare minimum required for "sky-integration" - all other integration techniques use basically the same strategy. I personally feel uncomfortable about the font-size of the document - really hard to decipher the text, making the understanding of the paper not easier.

Real Time Rendering of Atmospheric Scattering Effects for Flight Simulators
by R. S. Nielsen

Entry created by Andreas Jung.

Extensive master thesis which analyzes existing sky models with regard to flight simulator use. An analytic sky model is enhanced in a way, that makes it more suitable for flight simulation. [IMO] Out-of-the-box solution for interactive flight simulator sky. Also includes sourcecode. Best part: "Some researchers [7] have developed interactive rendering systems, using (HDR) tone mapping, but they are only slowly approaching real time performance and would not leave resources for the rest of the simulation in a flight simulator environment." - is no longer valid as of 2006. BUT: The paper weights 134 pages, and one has to read this in order to understand it. I have reviewed it only fragmentarily. A search on the word "night" returned no results, and that makes me afraid, as this seems to be the same drawback as with the other analytic sky model.

SilverLining
by Sundog Software

Entry created by Andreas Jung.

Commercial (but reasonably priced) cloud/sky-rendering SDK for C++. [IMO] Don't ask me how this integrates into an existing rendering pipeline. I think most developers prefer to developer their own cloud/sky techniques, OTOH this could be just what you need if you need to save time.

Midair Refueling Scene
by Voortmans Dirk

Entry created by Andreas Jung.

Belgium F-16's practicing midair refueling above overcast cloud layer.