The Multi-Referential constraint is a way to create a type of complex Parent/Child constraint, capable of letting you use more than one transformation reference as a Source object. This lets you reassign the transformation reference of one object to any other.
Unlike other constraints, you can create a Multi-Referential constraint using the Key Controls.
The Multi-Referential constraint is useful whenever you want to change a model’s reference point. This type of referential adjustment can occur in many different situations. Here are some examples:
You can use the Multi-Referential constraint in a scene with vehicles so that a character can walk to a car model (Global referential), climb into it, and drive it to another location (Car referential).
The character can then get out of the car, get into an elevator model (Elevator referential), take it to another floor, and get aboard a moving sidewalk model (Sidewalk referential), and so on.
You can use the Multi-Referential constraint to let characters manipulate props, for example making the character switch a prop from hand to hand, or carry props in a case strapped to the character’s body, such as a gun in a holster. With this constraint props can be caught, thrown, and so on.