setFogMode (Exp density) = do
   fogi FogMode (marshalFogMode' Exp')
   fogf FogDensity density
setFogMode (Exp density) = do
   fogi FogMode (marshalFogMode' Exp')
   fogf FogDensity density
setFogMode (Exp density) = do
   fogi FogMode (marshalFogMode' Exp')
   fogf FogDensity density