Tried to create realistic cloudscape for my recent demoreel, not fully satisfied though, have got some interesting ideas.
Cloud shapes are modelled and placed in Houdini, exported as separated vdb files(for-loop without any code), automatically imported inside Maya using python snippet, and rendered with Vray for maya.
In real-life clouds, internal light scattering is strong and often valley areas are brighter, so I baked concave curvature as extra fields(temperature field in this case, since Vray volume shader is a blackbox) and used them for emissive source. It's not physically correct at all, quite efficient though.
Cirrus layers were created with Maya 2d fluids with built-in texture(wispy noise type works great), placed and rendered as 3d cards inside Nuke.
Main Road Post's Mikhail Lesin provides in-depth details of VFX production for Attraction. We will go right from the early stage of pre-production through all fascinating effects. How we generate an authentic city and then destroy it, develop design of alien exoskeleton and spaceship, make genuine clouds and atmosphere, and why we need to make a CG fighter pilot. At the end you will hear how we adjusted our work principles to accomplish all this with a relatively small team of 50 people in just 1 year.