First we must to establish a set of names for the three lights that we will use. When setting up a light system following the three point lighting rules you will need to have a Key Light, a Fill Light and a Rim Light.

Each one of these can be any of the lights that are creatable within Maya. Keep in mind there is no one-way to do this, but there are certain obtainable visuals that make it work or not work.

#1 Key Light
The Key Light in a scene or setting is where the majority of the light is coming from and this light should also have the strongest shadow. In an outdoor scene there can be many light sources, but during the day the Sun is the Key Light. If we were to change the setting to an indoor environment such as an office the Key Light could then be one of two light sources, the Lamp or the Computer Monitor. The difference would depend on the intensity of each comparatively and which sheds more light, which is personal preference. In either case the Key Light has to cast the strongest shadow because it is the strongest light source.

Below in this picture depicts the Key Light, it is Yellow. I am using the Spotlight within Maya for the Key Light in this scene.

#2 Fill Light
The Fill Light in this setting is a light source that is not too intense that will shed an overall light on the object. There are few to any times when the Fill Light should be casting a shadow. In an outdoor scene the fill light is the overall brightness of the day, shadows have light within them due to the Fill Light.

Below in this picture depicts the Fill Light, it is Blue. I am using an Ambient light within Maya for the Fill Light in this scene.

#3 Rim Light The Rim Light, or some call Back Light, is used to define the furthest edge of the form from the background. Sometimes the Rim Light casts shadows, which depends on the setting. The Rim Light in some situations is almost another Key Light in the scene. But should never be more intense or shed stronger shadows then the true Key Light. In a night scene a Rim light would be very useful to separate the shadows on a character from the dark background. This allows for the silhouette to be visible even when cast in shadow. The placement of this light is almost always the opposite angle in the scene as the Key Light’s.

Below in this picture depicts the Rim light, it is Red. I am using the Spotlight within Maya for the Rim Light in this scene.

Here are all three lights working together, notice how they give the object a more solid feeling. The object now has mass because of the shadow, light source. Also the sphere has depth because of the Rim light and solidity because of the Fill light.

Here are the same lights but now they are all in the same color family giving a more realistic lighting.