Procedural terrain splatmap

Hey guys, I`m trying to use the cellular automata to create one procedural texture for my terrain.
I already have the cellular automata thing working, but I`m facing some problems to apply the texture to the terrain.
I know that could be a lack of math envolved, since the resolution of the terrain and size are different, but I`m really facing big problem to figure out. Can someone give one idea ?

Code (CSharp):

1. void ApplySplat()
2.     {
3.         int normX;
4.         int normY;
5.  
6.         TerrainData terrainData = terrain.terrainData;
7.         float [, ,] splatmapData = new float[terrainData.alphamapWidth, terrainData.alphamapHeight, terrainData.alphamapLayers];
8.  
9.         for ( int x = 0; x < terrainData.alphamapWidth; x++ )
10.         {
11.             for ( int y = 0; y < terrainData.alphamapHeight; y++ )
12.             {
13.                 splatmapData[ y, x, 0 ] = 0f;
14.                 splatmapData[ y, x, 1 ] = 1f;
15.             }
16.         }
17.  
18.         for ( int x = 0; x < mapWidth; x++ )
19.         {
20.             for ( int y = 0; y < mapHeight; y++ )
21.             {
22.                 normX = Mathf.RoundToInt( ( ( x - terrain.transform.position.x ) / terrain.terrainData.size.x ) * terrainData.heightmapWidth );
23.                 normY = Mathf.RoundToInt( ( ( y - terrain.transform.position.z ) / terrain.terrainData.size.z ) * terrainData.heightmapHeight );
24.  
25.                 splatmapData[ normY, normX, 0 ] = _map[ x, y ] ? 1f : 0f;
26.                 splatmapData[ normY, normX, 1 ] = _map[ x, y ] ? 0f : 1f;
27.             }
28.         }
29.  
30.         terrainData.SetAlphamaps( 0, 0, splatmapData );
31.     }

Result of the function above:

 

Bump ?

 

Found one solution
Well just posting for if someone face the same problem.
My problem was that the texture resolution should have the same size of the terrain, which should be multiples of 8.

64 / 128 / 256 / etc...