Save terrain grass data

Hi,

I have no idea how to save Unity terrain grass placement data. I can store every other data but not this. Here's my code

 TerrainData tdata = new TerrainData ();
         tdata.heightmapResolution = ter.terrainData.heightmapResolution;
         tdata.size = ter.terrainData.size;
         tdata.alphamapResolution = ter.terrainData.alphamapResolution;
         tdata.baseMapResolution = ter.terrainData.baseMapResolution;
             
         tdata.SetDetailResolution (ter.terrainData.detailResolution, 8);
         // Generate the heightmap
         tdata.SetHeights (0, 0, ter.terrainData.GetHeights (0, 0, ter.terrainData.heightmapWidth, ter.terrainData.heightmapHeight));
         
         tdata.splatPrototypes = ter.terrainData.splatPrototypes;
         
         tdata.treePrototypes = ter.terrainData.treePrototypes;
         tdata.treeInstances = ter.terrainData.treeInstances;
  
         tdata.wavingGrassAmount = ter.terrainData.wavingGrassAmount;
         tdata.wavingGrassSpeed = ter.terrainData.wavingGrassSpeed;
         tdata.wavingGrassStrength = ter.terrainData.wavingGrassStrength;
         tdata.wavingGrassTint = ter.terrainData.wavingGrassTint;
  
         tdata.GetDetailLayer(0, 0, ter.terrainData.detailWidth, ter.terrainData.detailHeight, 0);
         
         AssetDatabase.CreateAsset(tdata, "Assets/Terrains/"+ter.name+".asset");
         AssetDatabase.SaveAssets();
         
         
         
         // Now if we have splatmaps for this terrain, time to load them
         float[,,] splatarray = ter.terrainData.GetAlphamaps(0,0,ter.terrainData.alphamapWidth-1, ter.terrainData.alphamapHeight-1);
         SplatPrototype[] prototypes = ter.terrainData.splatPrototypes;
  
         Debug.Log (ter.terrainData.detailPrototypes.Length);
         details = new List<DetailPrototype>();
         for(int i = 0; i < ter.terrainData.detailPrototypes.Length; i++) {
             DetailPrototype prototype = new DetailPrototype();
             prototype.prototype = ter.terrainData.detailPrototypes[i].prototype;
             prototype.prototypeTexture = ter.terrainData.detailPrototypes[i].prototypeTexture;
  
             prototype.dryColor = ter.terrainData.detailPrototypes[i].dryColor;
             prototype.healthyColor = ter.terrainData.detailPrototypes[i].healthyColor;
             prototype.noiseSpread = ter.terrainData.detailPrototypes[i].noiseSpread;
             prototype.renderMode = ter.terrainData.detailPrototypes[i].renderMode;
             prototype.usePrototypeMesh = ter.terrainData.detailPrototypes[i].usePrototypeMesh;
             prototype.minWidth = ter.terrainData.detailPrototypes[i].minWidth; 
             prototype.maxWidth = ter.terrainData.detailPrototypes[i].maxWidth;
             prototype.minHeight = ter.terrainData.detailPrototypes[i].minHeight;
             prototype.maxHeight = ter.terrainData.detailPrototypes[i].maxHeight;
             details.Add(prototype); 
         }
  
  
         TerrainData td = (TerrainData)AssetDatabase.LoadAssetAtPath("Assets/Terrains/"+ter.name+".asset", typeof(TerrainData));
         
         
         td.splatPrototypes = prototypes;
         td.detailPrototypes = details.ToArray();
         td.RefreshPrototypes ();
         td.SetAlphamaps (0, 0, splatarray);
         
         AssetDatabase.SaveAssets();
         AssetDatabase.Refresh();
         
         Debug.Log (td.detailPrototypes.Length);
         ter.GetComponent<Terrain> ().terrainData = td;
         ter.GetComponent<TerrainCollider> ().terrainData = td;