ok. I’ve been working on a simple little planet animation, and in doing so have been going through a lot of atmosphere tutorials. for the most part, they all have pros and cons. Halos give u the nice falloff on the edge, using a transparent sphere gives you an easy way to get the fresnel, and a great tut that inspired me uses the node editor as well as a neat ramp shader trick. These are all great, the one that worked best (the ramp shader one) was just rediculously hard for me, but in trying to figure it out, I made a new way that I think is better. It is also very simple.
First, make your planet (if u want to know how to do that check out env’s tutorial). Next, make your atmosphere sphere. Now make a new scene that is the copy of the original (you might want to do this after you’ve done any animation or camera movement because it has to stay the same in both scenes).
Put both scenes as render layers in the node editor. (add>input>render layer). now, from the render of the planet, I added a brightness/contrast modifier because the eventual image is really dark after the two get put together.
Next, attach 2 “Soften” filters to the atmosphere. After you’ve done this, mix the two together (I used the mix>screen option because that’s what the tutorial I looked at said)
Now, this might be fine, if it isn’t I added another brightness modifier to the end and brightened it up some more.
Render, and viola!
I’ll get some pics shortly…