An intensity curve or an expression can be used to control decay. You can also create a custom brightness decay rate using an intensity curve. You can edit curves in the Expression or Graph editors.
To create a custom brightness decay
Maya creates an Intensity Curve node and connects it to the Intensity attribute.
You can create a custom color decay rate using a set of color curves (a red curve, a green curve, and a blue curve).
To create a custom color decay
Maya creates a RedCurve node, a GreenCurve node, and a BlueCurve node and connects them to the Color attribute.
You can edit intensity curves or a set of color curves either in the Attribute Editor or in the Graph Editor. Intensity or color curves display as a table of values in the Attribute Editor.
To view the table for an Intensity Curve in the Attribute Editor
To view the attribute table for Color Curves and the Intensity curve (after you create them)
When creating intensity and color curves for a light source, IPR Render the scene or part of the scene to get instant feedback on the changes you make to the light’s intensity and color curves.
To work with Intensity or Color curves in the Graph Editor