The LodGroupNode contains a collection of scene nodes sorted by distance (see property Levels). Each entry represents a level of detail (LOD). A LOD may consist of a single scene node or an entire tree of scene nodes. The Levels collection of LODs is empty by default. LODs can be added or removed during runtime.

Pose (position and orientation) and scale of the individual levels of detail are synchronized with the LodGroupNode. When a scene node is assigned to the LodGroupNode its local pose and scale is overwritten!

LOD0, LOD1, ... LODn-1:
LODs can be accessed by index. The LOD with index i is called LODi. By definition, LOD0 is the highest level of detail and LODn-1 is the lowest level of detail.

Nested LOD Groups:
LOD groups can be nested. That means a LOD may contain another LodGroupNode in its subtree.

LOD Distances:
LODs are selected based on the current camera and the distance to the camera (see method SelectLod(RenderContext, Single)). The LOD distances stored in the LodCollection are view-normalized distances. This means that distance values are corrected based on the camera's field-of-view. The resulting LOD distances are independent of the current field-of-view. See GetViewNormalizedDistance(Single, Matrix44F) for more information.

The camera that serves as reference for LOD distance computations needs to be stored in the render context: See property LodCameraNode.

In addition, the render context provides additional LOD settings: see properties LodBias, LodBlendingEnabled, LodHysteresis.

IMPORTANT:
To avoid unnecessary computations the LOD selection is updated only once per frame and camera. If the position or projection of the camera is modified during rendering, the method InvalidateViewDependentData needs to be called. Likewise, if LODs are modified, added, or removed during rendering, InvalidateViewDependentData needs to be called.

However, InvalidateViewDependentData may affect other scene nodes. It is therefore not recommended to modify the camera or the LOD node during rendering of a frame! Only call InvalidateViewDependentData if absolutely necessary.

Reference