Free Blender Rayleigh Scattering Shader
Joschka Bläker writes:
You know how you see that beautiful orange haze on pictures of earth from space where the sun is going down behind the horizon?
That haze is caused by something called “Rayleigh Scattering”, something Blender does not currently support, not natively at least, and it’s the biggest hurdle to get from stylized planet renders to realistic looking ones.
In my latest work I created a semi-realistic looking earth
Look closely and you will notice that exact same orange fade on the horizon.
To get to the point: I put in some effort and made a usable shader out of it and it’s publicly available as CC-0! Cool beans!
I’m excited to see what you come up with!
Happy Blending,
Joschka
Thanks man!
I´m sure it will be useful at some point! :D
Thank you for this. Just a detail, you talk twice about an orange haze and I only see a blue haze, unless I don’t know what you mean by horizon. Also it says on the Internet that the Rayleigh scattering is what gives the sky/atmosphere it’s blue color so I’m really confused. I guess I will have to try the shader to find out, but again thank you for the contribution.
On the land as it transitions between day and night – areas that would be seeing the sun setting – it looks good!
Hey!
Basically what the rayleigh scattering means is that when the light passes through the particles in the air, some wavelengths are absorbed like the longer ones (red) and only the short ones pass through, hence the sky is blue. Now when the light angle is more steep like on a sunset, the light has to pass through much more air than when the light comes perpendicular to the atmosphere. Since it passes through more air, other wavelengths are absorbed, this time shifting more towards the short ones while longer ones pass through. That is why the sky looks reddish-orange on a sunset.
Now on a planetary scale this is one of those unconscious things that make a big difference but are actually hard to spot without a comparison, so try and compare my render from above tho this one that I rendered with a uniformly color atmosphere:
https://i.imgur.com/THVeLU4.png
Notice how it still looks good, but more like a stylized sci-fi version of earth. That difference is only made by the rayleigh scattering giving the atmosphere a non-uniform color.
Thank you for the explanation and the comparison render, I understand now :) I also downloaded the shader and I see how the effect works now, again thank you for this.
It looks good, but is this the only real use case scenario for it? Or would it maybe work in a scene where there’s a “sun” of some sort down on the horizon?
That will definitely work, though keep in mind this is mainly just a color shader, you will need to use it on a volumetric atmosphere to get the actual scattering through the atmosphere, the shader then provides the more or less accurate coloration of that volume.
It’s main intended purpose is indeed solely the coloration of planetary rayleigh scattering, but that doesn’t mean it can’t be used for other effects, since all colors and parameters are customizable you can get some very cool looking abstract effects with it!
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