Programatically changing the tileSize of a SplatPrototype

Question

I have a script to which I add a Terrain object (I drag and drop the terrain in the public Terrain field).

The Terrain is already setup in Unity to have 2 PaintTextures: 1 is a Square (set up with a tile size so that it forms a checkered pattern) and the 2nd one is a grass image:

alt text

Also the Target Strength of the first PaintTexture is lowered so that the checkered pattern also reveals some of the grass underneath.

Now I want, at run time, to change the Tile Size of the first PaintTexture, i.e. have more or less checkers depending on various run time conditions. I've looked through Unity's documentation and I've seen you have the Terrain.terrainData.SplatPrototype array which allows you to change this. Also there's a RefreshPrototypes() method on the terrainData object and a Flush() method on the Terrain object. So I made a script like this:

 public class AStarTerrain : MonoBehaviour {
 
     public int aStarCellColumns, aStarCellRows; 
 
     public GameObject aStarCellHighlightPrefab;
     public GameObject aStarPathMarkerPrefab;
     public GameObject utilityRobotPrefab;
     public Terrain aStarTerrain;
 
     void Start () {
             //I've also tried NOT drag and dropping the Terrain on the public field 
             //and instead just using the commented line below, but I get the same results
         //aStarTerrain = this.GetComponents<Terrain>()[0];
         Debug.Log ("Got terrain "+aStarTerrain.name);
 
         SplatPrototype[] splatPrototypes = aStarTerrain.terrainData.splatPrototypes;
         Debug.Log("Terrain has "+splatPrototypes.Length+" splat prototypes");
         SplatPrototype aStarCellSplat = splatPrototypes[0];
         Debug.Log("Re-tyling splat prototype "+aStarCellSplat.texture.name);
         aStarCellSplat.tileSize = new Vector2(2000,2000);
         Debug.Log("Tyling is now "+aStarCellSplat.tileSize.x+"/"+aStarCellSplat.tileSize.y);
         aStarTerrain.terrainData.RefreshPrototypes();
         aStarTerrain.Flush();
     }
 
 //...

Problem is, nothing gets changed, the checker map is not re-tiled. The console outputs correctly tell me that I've got the Terrain object with the right name, that it has the right number of splat prototypes and that I'm modifying the tileSize on the SplatPrototype object corresponding to the right texture. It also tells me the value has changed. But nothing gets updated in the actual graphical view.

So please, what am I missing?

Answer 1

To change any property of any SplatPrototype of a terrain, duplicate the existing array of SplatPrototypes, ie create a new array with different instances inside, but with the same textures, tile offsets and size. Then you can change any property of the prototypes you need. Finally, assign that array back on the TerrainData.

No need to Flush() or RefreshPrototypes().

Caution: all changes made from code on a terrain while the game is running in the editor are persistent. So don't delete all your SplatPrototypes and don't mess them up by code, if you want to keep them after you stop the game in the editor.

Tested and works in Unity 4.5.4

 SplatPrototype[] oldProtos = terrain.terrainData.splatPrototypes;
 SplatPrototype[] newProtos = new SplatPrototype[oldProtos.Length];
 for(int i=0; i<oldProtos.Length; i++) {
     SplatPrototype oldProto = oldProtos[i];
     SplatPrototype newProto = new SplatPrototype();
     newProtos[i] = newProto;

     // Change what you need here
     newProto.texture = oldProto.texture;
     newProto.tileSize = oldProto.tileSize;
     newProto.tileOffset = oldProto.tileOffset;
     newProto.normalMap = oldProto.normalMap;
 
 }
 // Change what you need here
 terrain.terrainData.splatPrototypes = newProtos;

Answer 2

After working with terrains a bunch recently, I have found it's basically impossible to modify the member data of a splatPrototype directly.

What you should be able to do, however, is create a temporary splatprototype array that is basically the same as your original splat prototypes, but with different tileSize.

I've only used this method to set the terrainData of newly created terrain that hasn't had any splatPrototypes set. It may be that this doesn't work on terrain that already has has its splatPrototypes set. Sorry if that's the case, but I guess it's worth a try nonetheless.

 //After you've gotten your terrain and stored your terrains SplatPrototypes, use this code
 //Declare this first line however it needs to be in C: I'm not a C expert, 
 //so I only know the way of doing it in Unityscript
     tempSplat : SplatPrototype = new SplatPrototype();
                     
     tempSplat.texture = splatPrototypes[0].texture;
                         
     //Uncomment this line if using Unity 4.0 or greater. normal maps were only added in 4.0.                    
     //tempSplat.normalMap = splatPrototypes[0].normalMap;
                         
     tempSplat.tileSize.x = 2000;
     tempSpat.tileSize.y = 2000;
     
     tempSplat.tileOffset.x = splatPrototypes[0].tileOffset.x;
     tempSplat.tileOffset.y = splatPrototypes[0].tileOffset.y;
     
     splatPrototypes[0] = tempSplat;
     
     aStarTerrain.terrainData.RefreshPrototypes();
     aStarTerrain.Flush();

Programatically changing the tileSize of a SplatPrototype

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