Intriguing aurora

[zzu]

Terragen has pretty realistic atmospheric shader by default, but a globe with a blue glow is becoming a cliche in visual industry. I kinda want to know the possible ways to create an aurora effects like the one in the picture, maybe a double atmosphere, if that's plausible? Any plausible advice is warmly welcomed.

[AP]

https://en.wikipedia.org/wiki/Airglow

That should be possible to achieve such an effect. Perhaps I can help with that.

[zzu]

Hi ApP, it'll be great if you can share some experience regarding this special technique.

[AP]

Here is a basic idea how this currently looks. I would recommend adjusting the cloud density, sharpness and altitude to start with for any possible improvements. I have no idea as to how to prevent the effect from being effected by the day side light. Perhaps some other ideas may come forth. The crude city lights are just for reference only.

[zzu]

Thank you AP for putting efforts into this, I'll study your file soon. I did a bit more research regarding the composition of airglow, here is the basic components, feel free to take a look.

One thing I got from this image is that we need basically 3 layers of airglow, first is green, then yellow and orange, and none of them have sharp edges, just naturally fading away.

Another question is, where the green tint comes from, I didn't find any green color setting in the nodes?

[AP]

I am not certain as to how to approach the other colors without having a lack of dark fading over the night side. The photographs shown are long exposure so the lighting is somewhat exaggerated. The green tint comes from the ambient color in the cloud node as the diffuse is very high but there could be other approaches to the coloring. Try the main diffuse colors and see what occurs.

[zzu]

Umm, is it possible to invert the  cloud layer, so it fades out into space?

[zzu]

I think I'm getting close now, may I ask how to render the clouds as an individual layer?

[Oshyan]

Here's an aurora setup I made quite a while ago, but still seems like a good starting point. Getting the bright green glowing color is not so hard. Creating the aurora shapes is harder, but if you just need a big diffuse glow, that should be easy with a low-octave, low-contrast fractal.

- Oshyan

[zzu]

Finally, I think this is what I expected, thanks to you AP. Also, I will check the file you posted, Oshyan.

[zzu]

At this point, I think the way to improve the current model would be adding a gradient to the glowing atmosphere, like the attached real image suggested. Any advice?

[AP]

That looks a lot better but now if you can have it glow on the night side and try to have far less on the day side as the glow would not be visible on the day side. In fact in reality it might not be visible at all on the day side but nothing wrong with some exaggeration.

[Oshyan]

I would simply suggest multiple cloud layers, one to simulate each layer of airglow. The reference image above suggests a deep, faint, red layer, and a narrower green, then yellow layer (3 in total).

- Oshyan

[AP]

I would simply suggest multiple cloud layers, one to simulate each layer of airglow. The reference image above suggests a deep, faint, red layer, and a narrower green, then yellow layer (3 in total).

- Oshyan

That could work well.

[zzu]

yea, the green is kinda intersecting with the red, need some gradient, any idea?

As regard to letting it glow only in the dark side, I'm thinking the possibility of adding a second sun, and let the sun only shine light on the cloud layer from the other side of globe, if that's plausible.