Understanding Object Copies, Instances, and References

When you copy an object, you create a new, independent master object and data flow resulting in a new named object. The copy duplicates all of the data of the original object at the time it is copied. The copy has no connection to the original object.

When you instance an object, you are displaying multiple named objects based on a single modified object. Each named object instance has its own set of transforms, space warp bindings, and object properties, but it shares the object modifiers and master object with the other instances. The data flow for an instance branches just after evaluating object modifiers.

Because instances share the same master object and object modifiers, changing the creation parameters or applying a modifier to any one instance changes all related instances.

When you reference an object, you split the object modifiers into groups of shared and unique modifiers. Like instances, references share, at minimum, the same master object and possibly some object modifiers. The data flow for a reference branches just after the object modifiers but then evaluates a second set of object modifiers unique to each reference.

The data flow for references depends on where in the modifier stack the reference is made. Each time you create a reference, the data flow branches after evaluating all of the current object modifiers and adds a container for another set of object modifiers. In the modifier stack you can see where branching occurs by looking for a gray line between modifiers. This is called the derived object line.

All shared modifiers are below the derived object line and are displayed in bold. All modifiers unique to the selected reference are above the derived object line and are not bold. The original object does not have a derived object line – its creation parameters and modifiers are all shared, and all changes to this object affect all references.

Because references share the same master object, changing the creation parameters for any reference object changes all related references.

The results of changing or applying a modifier to a named object reference depends on where in the modifier stack it is applied: