Here you have 4 different Atmospheres. The Objects are not included. Saved as *.tgc file. A detailed description for insert the files is included. So try it! Good price, good man! :) 
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This free download is two layers of clouds in clipfile format and, the same two layers, with an alternative layer(disabled), in .tgd format. The lower is the altocumulus layer. The upper, the cirrocumulus layer. The .tgd has an extra alternative ...  
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This is a free of charge TGD providing you with a very realistic overcast sky. This is not just an atmosphere clip file. You also need to use the "ray trace everything" and other quality settings in this file. Of course you can switch off "ray trace ...  
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For barnEbiss 
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