When writing a plug-in that derives from a base class, 3ds Max will expose much of the necessary functionality through the arguments to the virtual functions that you override. In cases where you need access to additional functionality provided by 3ds Max the global function GetCOREInterface12() can be very useful. This function returns a pointer to a global object of type Interface12, which provides access to much of the core functionality of 3ds Max.

Note: a lot of older code uses the function GetCOREInterface() which returns a pointer to an Interface object. Interface12 derives from Interface but provides additional functionality.