Detail 1.0, AA 3, GI 2/2
I have two ground level cloud layers for making that haze, both of them at quality 2.
I have RTA on, and receive shadows from surfaces on in all cloud layers and atmosphere itself. And I'm using soft shadows. I'm not in the same pc I have the .tgd file right now but I guess I had 18 samples for soft shadows.
This is the maximum size since I am using TG2 free... (Altough I would like too see it bigger too

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14 hour render on core i5.
Not sure if the pc entered sleep mode during this time, I wasn't using my pc, I left it rendering and came back in the other day to see the results (work pc

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One change I'm considering is to decrease foreground luminosity a little and increase overall contrast... Perhaps add a little more detail to the soil (small pebbles, cracks, etc, though I don't know how exactly to do this) and bring out the grass a little more. Also I would like to increase specular reflectivity a little on the ground. Perhaps I'll try a second iteration soon, gimme more suggestions if you want!

Cheers