In versions prior to 3ds Max 5, there were only two possible shadow types - ShadowMap and Raytraced shadows. The type was controlled by a single boolean property which caused the respective ShadowGenerator to be assigned to the light implicitly.
Starting with 3ds Max 5, a larger number of possible shadow map generators have been introduced. The access to the shadow generation of all lights has been extended to allow explicit assignment of an instance of a shadow generator class.
The shipping shadow generator classes are:
In order to assign a shadow generator to a light, you have to create an instance of one of the above classes by calling the constructor with a pair of parentheses and assign the instance to the .shadowGenerator property of the light. Also see When do I use () after a function?
EXAMPLE
$Omni01.shadowGenerator = Area_Shadows()
For more details, see the Light Common Properties, Operators, and Methods topic.