Terrain LOD is the distant ground and large (cell sized) bodies of water.
Use xLODGen terrain LOD beta to generate terrain LOD meshes and textures. See xLODGen for more.
At the moment DynDOLOD does not create, update or otherwise change terrain LOD or water LOD.
Terrain LOD meshes only contain the information where to show LOD water. How the LOD water looks for an entire worldspace is defined by worldspace record. How water looks in an active cell is defined by the cell record. The worldspace and cell records from the winning plugins are copied to create the DynDOLOD or Occlusion plugins. Hence the load order needs to be finalized before generating the LOD patch with DynDOLOD and/or generating Occlusion.esp.
Object LOD generation uses terrain LOD meshes to optimize the object LOD meshes by removing any triangles that are below the terrain or water planes. Hence terrain LOD should be generated before object LOD.
In Skyrim Special Edition and Skyrim VR the terrain LOD meshes are being lowered in the distance - which is baked into a shader. Presumably this is done to counter z-fighting with object LOD.
In any Skyrim version, the full terrain textures fade in a fixed circle around the current center cell to the diffuse terrain LOD texture. This fade does not use the normal map terrain LOD texture.
Settings
The distances of the terrain LOD levels can be controlled with below INI settings - either in the DynDOLOD SkyUI MCM or the Prefs INI.
fSplitDistanceMult=multiplier of object LOD Levels
The multiplier multiplies the object LOD distances for the different LOD levels in order to define the distances for the terrain LOD levels. If the multiplier is near 1, both object LOD and terrain LOD switch their LOD levels at the same, which makes it even more obvious.
Technical Information
Terrain LOD meshes generation uses the height data found on the first LAND record for a cell and the default land height from the WRLD record as fallback.
The water LOD that is generated as part of the terrain LOD meshes generation with xLODGen uses the water height found on the CELL record and default water height found on the WRLD record as fallback. The default LOD water height on the WLRD record is not used by xLODGen.
The terrain LOD texture generation uses the texture layers, the vertex color and vertex normal data found on the first LAND record for a cell. The texture layers link to LTEX records which link to TXST records which contain the actual texture filenames being used.
Terrain LOD Files
Terrain LOD meshes:
..\Meshes\Terrain\[WORLDSPACE]\[WORLDSPACE].*.*.*.BTR
Terrain LOD textures:
..\Textures\Terrain\[WORLDSPACE]\[WORLDSPACE].*.*.*.DDS
First * is the terrain LOD level 4, 8, 16 or 32. Second and third * are the cell coordinates of the west/south cell for the area the file covers.