4. Clouds texture

A cloud is as shiny as cotton therefore the texture has a very low specularity and glossiness. The shape of the cloud formations is defined by the map Earth-clouds2700.jpg. It is used as an opacity map: clouds are opaque but the surface between them is transparent.

Then a "mix" bump map is used to create the "cottonness" of the cloud formations. A regular noise with a medium wavelength creates the smaller puffs and a turbulent noise with a longer wavelength suggest bigger cloud formations.

Now, when rendering the clouds I spotted a problem: at the border between light and shadow - where the light rays hit the clouds at a very low angle - the bump map generated black spots on the cloud texture itself (ray-traced shadows) that were nowhere near photo-realistic. To tackle the problem I used the falloff texture again to apply bump to clouds proportionately to the level of light. In the transition area between light and shadow the level of bump decreases and does not generate those ugly black spots. I manually adjusted the curve using the output tab of the falloff material to achieve the best possible effect.

5. Atmosphere texture

Now to create the effect that does most of the work in creating the photo-realistic effect. The software helps us a lot with a predefined Falloff material that can simulate the Fresnel effect. The Fresnel effect is plugged as a diffuse map. Unfortunately, the Fresnel material options only offer 2 colors for the effect therefore the output characteristics have to be tweaked quite a bit to create the desired complex green-to-blue-to-black gradient.

Coming Soon...

The next step is the animation, creating the correct axis to spin the earth as well as the way the cloud layer will work in relation to the spin. This is the complicated bit, describing movement and action when you are dealing with 3D space. Plans are to have some preview renders done soon for animation tests. These will be simple renders (no textures or lighting & no-post effects) to give an idea of how the shot will work.