Atmosphere Scattering Simulation Solution (AS3) is the tool which can physical simulate any height of atmosphere for your terrestrial planet.
It is based on Optical Depth Lookup Table which was introduced by Siggraph’93 paper “Display of The Earth Taking into Account Atmospheric Scattering” and GPU Gem2 “Accurate Atmospheric Scattering”. If you want to know more about the algorithm of this tool please check those papers and visit my blog: Flexible Physical Accurate Atmosphere Scattering
The goal of this tool is build a physical accurate atmosphere scattering phenomenon both from space and inside atmosphere, All of AS3 shaders can work both outer and inner atmosphere. the shaders not only work in SM3.0 but also in SM2.0. It included different solution for your need.
The results which were generated by Lookup table are much better than scale function (the GPU Gem2’s SM2.0 sample), it much more accurate and more realism. As following earth simulation, it is hard to say which one is the real earth picture (There are two pictures are real photographic):
There is a Demo to show your the Earth Simulation result in real-time:
Flexible Physical Accurate Atmosphere Scattering
You can create any atmosphere height ratio planet and also physical accurate via this tool, You can get extreme thick atmosphere even not exist in the world (there will have some interesting result, you can check in my blog).
There is another Demo to show you the result of different atmosphere height ratio planets in real-time. You can change the sun direction, camera FOV and fly in atmosphere to see sunset light scattering inside sky (you can tweak G value to see the difference of scattering direction ratio when you fly in atmosphere):
(Left: G = -0.99, Right: G = -0.75)
Real-Time Atmosphere Height & Scattering Changing
After version 1.2 you can real-time change the atmosphere height and scattering and it supports SM2.
Easy To Use
The AS3 tool is very easy to use, just one click you will get your new planet in your scene after you select sun light and make sure all setting is correctly.
Recommended Unity Version
Windows: Latest version than Unity3D 3.5
MAC OS X: Latest version than Unity3D 4.3 (since Unity3D fixed GLSL issue in this version)