You can create meshes with different levels of detail in an external 3D application for use with Unity’s LOD system. If you name these meshes correctly, Unity automatically creates and configures a GameObjectThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary with LOD groupA component to manage level of detail (LOD) for GameObjects. More info
See in Glossary component for them when it imports the Model.
To import a Model with LODThe Level Of Detail (LOD) technique is an optimization that reduces the number of triangles that Unity has to render for a GameObject when its distance from the Camera increases. More info
See in Glossary level into Unity, you must do the following:
In your external 3D application, follow the application’s process to create as many LOD meshes as you need.
Export your Model as an FBX file. Alternatively, if you are using Maya, export the mesh group directly into Unity; to do this, go to File > Send to Unity > Selection.
Import the FBX into Unity. Unity recognizes the grouped Meshes and naming convention, and automatically creates an LOD Group component with the appropriate settings.
To learn more about importing models, see Importing models.
To learn more about creating and exporting LOD Meshes in Maya, follow the Unity tutorial Creating LODs in Maya.