I am attempting to create a reasonably realistic fully animatable model of the earth for one of my ongoing projects(see my sig). I am currently stuck on how to get an atmosphere that is only visible at the edges, but also fades out at the extreme edge, to get that “fuzzy” look. Getting it to be only visible at the edges is easy, you just need a simple fresnel effect with ray transparency. Getting it “fizzy” however, is probing much more difficult.
I think it should be able to be done with basic alpha and material nodes, but due to my unfamiliarity with the material nodes, a solution has so far eluded me. What i am wanting is to be able to vary the alpha(vary completely, from 0 to 1, not just mix a new value in like with the non node color ramps), preferably with a color ramp node, based on the angle between the normal to the surface, and the camera. That way, for extreme angles, i can make it completely transparent, fade that to mostly opaque for slightly smaller angles, then fade to transparent for the majority of the atmosphere sphere.
Any help with this would be greatly appreciated.