A surface that is not exposed directly to a light source still will be visible if nearby objects are illuminated. In our basic illumination model, we can set a general level of brightness for a scene. This is a simple way to model the combination of light reflections from various surfaces to produce a uniform illumination called the ambient light, or background light.
Ambient light has no spatial or directional Characteristics. The amount of ambient light incident on each object is a constant for all surfaces and over all directions.
