In this image, fog effect is still there even I disable it in Environment object setting



Using "Fog.draw = false" does not help.

How can I get rid of this fog ?

make sure you "set" the environment.

changing the "Environment" members requires to call void set (); // apply these settings to graphics (this will call 'set' on all members of this class)

Perhaps this is blending to sky color.
Check Sky tab and Frac/fraction parameter.

Thanks yes it is, sky related