This might be because your scene includes the default camera and lights. Unity started importing those with its default Blender import script starting sometime in Unity2019 and it will break a lot of prefabs.
You can either a) remove the Camera and Light and everything except the LOD group objects (properly named), or you can modify the Blender import script embedded in Unity. This means you would need to re-modify it every time you switched to a new version of Unity, but I was lazy and I do this. Here’s more about that idea:
Blender3D import FBX:
https://discussions.unity.com/t/832303/2
The script that Unity uses:
./Hub/Editor/2020.2.1f1/Unity.app/Contents/Tools/Unity-BlenderToFBX.py
More on fixing it:
https://discussions.unity.com/t/839045/4
Blender is a right-handed coordinate model, Unity is a left-handed.
When you import any Blender object you’ll see its rotation is (-90, 0,0) (or close to that).
To get a tree working with terrain, the tree must be modeled to look upright when rotation is (0,0,0) in Unity.
Try making your tree in Blender so that “up” is actually +Y on Blender’s coordinates (green line positive).
This basically involves:
- load your tree
- enter EDIT mode (not OBJECT mode!)
- select all
- make sure your pivot is correct (probably should be (0,0,0))
- rotate geometry -90 on X (keys are R X -90)
- leave EDIT mode
- save the laid-down tree
That tree should paint properly with Unity terrain.
