In the real world, a light’s brightness is strongest at the light source and decreases or decays further away from the light source. In Maya, a light’s brightness decays only if decay is turned on. The light’s color, however, remains the same no matter how far it is from the light source.
You can select a preset brightness decay rate by setting the Decay Rate attribute for a light. The preset brightness decay rates are usually good enough to create most types of lighting effects. In some cases, however, you may want to create a unique type of brightness decay.
Custom intensity and color decay rates
You can also create decay effects not seen in the real world. For example, you can use a custom Intensity curve to make a spot light’s brightness increase further away from the light source, or you can use a custom Color curve to make the color of a spot light change with distance.
You can use this technique only for a Spot Light.
Intensity curves and color curves are graphical representations of a light’s brightness and color with distance. You can use the Graph Editor to view them. The vertical axis represents the intensity or color intensity value, and the horizontal axis represents distance from the light source. (Intensity curves and color curves are similar to animation curves, except the horizontal axis of an animation curve represents time.)