Index of refraction: light speedy variation when it hit solid objects like glass, water and other objects, for the air the IR is 1:

http://hyperphysics.phy-astr.gsu.edu/Hbase/geoopt/refr.html

Some more IE for simulate better surfaces:

http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/indrf.html

For the cloudy glass just change the color to white, I thin will work better.

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