There are many procedures and special effects that you can perform on models once they are a part of a 3D member. Some of these affect the appearance of models, while others have to do with the balance of quality versus performance.
Level of detail, or “lod,” is a way to get Director's 3D engine to remove polygons from a model so that it renders faster. It only works on models imported from a 3D graphics program, not primitives.