Hi, it is one of the shots of my personal project. All the clouds are created and rendered (3K) in Terragen. The scene only consists of 1 atmosphere, 1 Easy Cloud (front) and 1 Easy Cloud (top).
I mainly separated 4 layers:
atmosphere with sun (single frame)
atmosphere without sun (single frame)
front cloud (sequences)
top cloud (sequences)
GI cache generation process took 30 mins per frame with all atmospheric items shown. For "front cloud" and "top cloud" layers, each took 30 mins to render its own layer with lighting passes (alpha, direct, indirect and cloudRGB). When rendering a specific cloud layer, all other clouds which are not involved in that layer has been set their primary visibility off.
The shot is composited in Nuke. "atmosphere with sun" layer subtracts from "atmosphere without sun" layer to get the sun only layer.
If you feel interested, you can click the following tags to see more:
shorturl.at/fpQT9
Cool animation, looks very realistic.
Thanks Dune. The top cloud still has some flickering issues, I am trying a higher quality render only for that layer.