How do you add terrain textures at runtime?

this was a quick test script that seemed to work. Please note this is in uJS :

 #pragma strict
 
 import System.Collections.Generic;
 
 public var terrain : Terrain;
 private var terrainData : TerrainData;
 
 public var newTerrainTexture : Texture2D[];
 var terrainTextureList : List.< SplatPrototype >; // private, public for testing
 
 function Start() 
 {
     if ( !terrain )
     {
         terrain = Terrain.activeTerrain;
     }
     
     terrainData = terrain.terrainData;
     
     // store existing textures
     var i : int = 0;
     
     terrainTextureList = new List.< SplatPrototype >();
     
     for ( i = 0; i < terrainData.splatPrototypes.Length; i ++ )
     {
         terrainTextureList.Add( terrainData.splatPrototypes[i] );
     }
     
     // add new textures
     var newSplat : SplatPrototype;
     
     for ( i = 0; i < newTerrainTexture.Length; i ++ )
     {
         newSplat = new SplatPrototype();
         
         newSplat.texture = newTerrainTexture[i];
         newSplat.tileSize = new Vector2( 15, 15 );
         newSplat.tileOffset = Vector2.zero;
         
         terrainTextureList.Add( newSplat );
     }
     
     // reapply splats to terrain
     terrainData.splatPrototypes = terrainTextureList.ToArray();
     
     // you may also need
     // terrain.terrainData.RefreshPrototypes();
     // terrain.Flush();
 }

Unity Scripting References :

• http://docs.unity3d.com/Documentation/ScriptReference/TerrainData-splatPrototypes.html

• http://docs.unity3d.com/Documentation/ScriptReference/SplatPrototype.html