Algodoo

A test forest scenery including clouds move (even if this is paused).
If you want this to your scene then give credit.
Cloud image: Algodoo
Tree image: https://www.google.com/search?biw=2049&bih=1021&tbm=isch&sa=1&ei=6fNZWtOzJ4u98QW0-a6IDA&q=tree&oq=tree&gs_l=psy-ab.3..0i19k1l10.105600.106204.0.106729.4.4.0.0.0.0.211.411.2-2.2.0....0...1c.1.64.psy-ab..2.2.410....0.z8tSVu8wx3Y#imgrc=k9Ntjo6omnnrjM:

You don't need to copy-paste to your new scene. You could do anything and save the scene.