You can use two kinds of externally referenced files (XRefs): XRef Objects and XRef Scenes. Using these external references allows for a team approach to animation, where the modeling, materials, and animation can be handled in separate files by different artists. It can also make large files much easier to deal with through the use of proxy objects.
You access XRef Objects and XRef Scenes from the File menu.
The two types of references have distinct purposes:
Referenced scenes bring in a file that cannot be selected or inadvertently changed. An animator can bring in the environment or set as a referenced scene and won’t have to worry about mistakenly selecting walls and floors while trying to animate legs and arms.
The file renders as part of the animation, but will not hinder the workflow. Referenced scenes can be bound to an object in the scene so you can scale, rotate, or reposition the scene if necessary.
Referenced objects appear in the scene and can be animated. Depending on the object's XRef settings, you might or might not be able to edit the object’s modifier stack, as well as any manipulators applied to the object. You can add modifiers or transform animation to the referenced objects, but you cannot inadvertently change the model’s structure. Referenced objects allow for the substitution of a proxy object, so you can animate a low-polygon version of a complex model and then render the polygon-intensive version.
In 3ds Max 8, you can also XRef materials. This is part of the process of referencing objects, or you can also use the special XRef material.
Note: Any atmospherics applied in an XRef object's source file will be carried into the scene.
The use of referenced objects and scenes allows you to continue to work on models and materials while the animation process is under way. You can choose to have the models and materials update automatically, as soon as changes are saved to the original file, or to update manually, on demand.
There are also tools for easy conversion of scene objects into referenced objects, and a button to merge referenced objects back into the scene as normal objects.
А если коротко и по-русски, то ты можешь делать каждую модель отдельно, а потом собирать их вместе в отдельной сцене. При этом можно собирать как из отдельных объектов так и из целых сцен (это в случае, если ты делаешь что-то вроде "Властелина колец"). Вопросы?