Unity 5: Create stand-in geometry for Terrain trees to bake correct lightmaps

PlaceTreeShadowCasters_LOD.cs

using UnityEngine;
using UnityEngine.Rendering;
using UnityEditor;

public class PlaceTreeShadowCasters 
{
	
	[@MenuItem ("Terrain/Place Tree Shadow Casters")]
	static void Run()
	{
		Terrain terrain = Terrain.activeTerrain;
		if (terrain == null ) 
		{
			return;
		}
		
		TerrainData td = terrain.terrainData;
		
		GameObject parent = new GameObject("Tree Shadow Casters");
		foreach (TreeInstance tree in td.treeInstances) 
		{
			Vector3 pos = Vector3.Scale(tree.position, td.size) + terrain.transform.position;
			TreePrototype treeProt = td.treePrototypes[tree.prototypeIndex];
			GameObject prefab = treeProt.prefab;

			Debug.Log ("tree : " + tree.rotation);
			GameObject obj = GameObject.Instantiate(prefab, pos, Quaternion.AngleAxis(tree.rotation * Mathf.Rad2Deg, Vector3.up)) as GameObject;
			MeshRenderer renderer = obj.GetComponentInChildren<MeshRenderer>();
			renderer.receiveShadows = false;
			renderer.shadowCastingMode = ShadowCastingMode.On;
			GameObjectUtility.SetStaticEditorFlags(obj, StaticEditorFlags.LightmapStatic);
			
			Transform t = obj.transform;
			t.localScale = new Vector3(tree.widthScale, tree.heightScale, tree.widthScale);
			t.rotation = Quaternion.AngleAxis (tree.rotation * Mathf.Rad2Deg, Vector3.up);
			t.parent = parent.transform;
		}
	}  
}