| Submitted by , posted on 20 January 2001 |

Image Description, by This is a screenshot of the sky rendering part of an engine i'm working on (for a future MMORPG) on my free time. In many games, i believe the sky is one of the most underestimated feature. It often takes a big part of the screen, so it ought to be nice-looking to maximize the player's enjoyment experience.
The engine supports almost any type of sky commonly used nowadays. For the background, static sky boxes (fixed images) are obviously proposed, but it is also possible to use a dynamic sky box (the colors of each pixel are then calculated from many parameters -time of the day, position of sun, haze, colors equations, etc.. -) or a dynamic sky dome. The deformation effects are taken into account when generating the textures, so you can look at 360 degres.
The clouds are based on layers of alpha-blended textured surfaces (planes or domes). It is possible to set the transparency, animation functions, speed, density of clouds, etc.. In addition, it is possible to define your own animations and effects (clouds morphing for example).
Technically, the textures are procedurally generated; many functions and filters are then applied to them to make them look like more realistic (sharpness, color, shadows and lighting on the clouds from the sun).
The two images shown above are based on a dynamic sky box and two clouds domes. The clouds are moving with the wind at different speed, and slowly disappear at the horizon. It is running extremely fast (60 fps -with vsync enabled- on a P200+Vaudoo2), since there are no more than 15 polygons, and it doesn't look too bad i think ( though it can always be improved ).
In the future, i hope to implement support for independant and true 3d volumetric clouds.
Have a nice day !
Brebion flavien

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