The direction and uniformity of the light has a strong affect on our ability
to recognise 3-dimensional objects. If an object is seen against a background
of similar brightness, then it can only be distinguished by the light and dark
areas the light creates on it surface.
If the light is too diffuse, no shadows are cast and the object looks blurred. If, on the other hand, it is too direct, the extreme contrasts can be unpleasent to the eye and can even cause optical illusions. This is important to know in places such as sport arenas and halls where fast ball games are played.
Good modelling is also recommended in public places. People's faces can only properly distinguished when the modelling ability of the lighting allows for it. See also Directionality of the lighting