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..::dynamic atmosphere::..

Throughout time, planetary bodies in 3D have had an atmospheric effect generated by a standard edge glow effect. However this yields a problem when the camera starts travelling towards or away from the surface of the planet as the glow size is fixed unless animated. There are ways around this of course, however what if we actually want to travel inside the atmosphere itself? This produces another main problem – getting the glow to adaptively “spread” above camera.

The key to creating the desired result, both dynamic in size and also so that we can travel through the atmosphere (following a spaceship, comet or (uhh) teapot coming to wipe us all out!) is to think a little more outside the box. We can use 3ds Max’s own volumetric system to simulate the atmospheric effects and control its distribution and size in 3D space using a volumetric light’s attenuation and decay for realistic effects. This also means that and close surfaces (eg the planet surface itself) will have some fogging applied to it, casting a nice desaturation of colour across its surface the further we view toward the horizon (air density desaturates colour – look out of the window to the horizon – you will notice that colours aren’t as prominent as those in the foreground), just as in real life, in addition to material effects to exaggerate it a touch such as overlaying additional material-based fogging, desaturation and opacity to blend in the atmospheric horizon volumetrics.

Our resulting scene setup is quite basic, but the key is to get a fine balance between inverse square decay settings, colour, volumetric effect density and attenuation, each of which depends on the size of the object(s) and scene scale. To add a bigger sense of scale to the scene to the close proximity shot illustrated I’ve also flattened out the surface a touch so that we get a more subtle curve around the horizon instead of a more pronounced one. The final scene has a basic camera animation applied, with an added Noise controller to its rotation, giving the effect that it is being buffeted around as it travels through the atmosphere. Note: due to copyright / distribution issues, the texture map has not been included with the scene. Please see the file properties of the accompanying 3ds max scene for information where to download it, and others.

Enlarge Screenshot The planet and atmosphere material is faded out using a Gradient Ramp map to remove any harsh edges on the horizon, therefore mixing nicely with the volumetric light effect.
Enlarge Screenshot The volumetrics are driven by a single Omni light, with its falloff controlled by an inverse square decay. When travelling through the “atmosphere”, we can see the effect update accordingly.
Download the max file! Zip file to accompany.

..::quick tip::..

Because of the close proximity of the surface of the planet, any cloud layers we add will look flat. Therefore try to use billboard particles or volumetrics for this effect.

Initially published: 3D World magazine, Issue 80, August 2006.

Copyright Pete Draper, August 2006. Reproduction without permission prohibited.