In The Sims series, light is provided in two ways. It can be provided by lights in a room or area. In addition, some objects are considered to be lit, at least when in use, and may provide a certain amount of light, at least in their immediate area.
Daylight is available for approximately half of a Sim day. The outdoors are lit during daylight hours, though some areas may be in shadow. Daylight can enter a room through windows and doors that contain windows. Light can pass over a half-wall, though the half-wall may cast a shadow.
Whether they're indoors or outdoors, Sims like to be in well-lit areas. In The Sims and The Sims 2, lack of light depresses the Room/Environment motive. In The Sims 3, it produces the "It's Dark" moodlet. However, some creatures, such as vampires, do not need light.
The light engine for The Sims 3 itself has provoked some controversy among players as light does not flow from one floor to another, and often does not flow off of lots, leaving harsh visible edges on buildings and sidewalks. A higher level of bloom was introduced with The Sims 3: Ambitions.