Terrain Terrain Layers API. Can you tell me the starting point?

Use of SplatPrototypes is deprecated. You will want to use the TerrainLayers portion of the Terrain/TerrainData APIs. So something like:

Code (CSharp):

1. public void AddTerrainLayer( Terrain terrain, TerrainLayer terrainLayer )
2. {
3.     // get the current array of TerrainLayers
4.     TerrainLayer[] oldLayers = terrain.terrainData.terrainLayers;
5.  
6.     // check to see that you are not adding a duplicate TerrainLayer
7.     for( int i = 0; i < oldLayers.Length; ++i )
8.     {
9.         if( oldLayers[ i ] == terrainLayer ) return;
10.     }
11.  
12.     // NOTE: probably want to track Undo step here before modifying the TerrainData
13.  
14.     TerrainLayer[] newLayers = new TerrainLayer[ oldLayers.Length + 1 ];
15.  
16.     // copy old array into new array
17.     Array.Copy( oldLayers, 0, newLayers, 0, oldLayers.Length );
18.  
19.     // add new TerrainLayer to the new array
20.     newLayers[ oldLayers.Length ] = terrainLayer;
21.     terrain.terrainData.terrainLayers = newLayers;
22. }

or you can use the PaintContext API in the UnityEngine.Experimental.TerrainAPI namespace.

Here are some examples: https://github.com/Unity-Technologies/TerrainToolSamples

 

Ah you mean to actually fill the alphamap with a terrain layer. I guess I only answered part of the question. Sorry about that.

You'd definitely want to use the PaintContext API (BeginPaintAlphamap and EndPaintAlphamap, specifically) or manually set the splat/alphamap weights using something like this:

Code (CSharp):

1.  
2. public void AddTerrainLayer( Terrain terrain, TerrainLayer terrainLayer )
3. {
4.     // get the current array of TerrainLayers
5.     TerrainLayer[] oldLayers = terrain.terrainData.terrainLayers;
6.  
7.     // check to see that you are not adding a duplicate TerrainLayer
8.     for( int i = 0; i < oldLayers.Length; ++i )
9.     {
10.         if( oldLayers[ i ] == terrainLayer ) return;
11.     }
12.  
13.     // NOTE: probably want to track Undo step here before modifying the TerrainData
14.  
15.     TerrainLayer[] newLayers = new TerrainLayer[ oldLayers.Length + 1 ];
16.  
17.     // copy old array into new array
18.     Array.Copy( oldLayers, 0, newLayers, 0, oldLayers.Length );
19.  
20.     // add new TerrainLayer to the new array
21.     newLayers[ oldLayers.Length ] = terrainLayer;
22.     terrain.terrainData.terrainLayers = newLayers;
23. }
24.  
25. public void FillTerrainLayer( Terrain terrain, TerrainLayer terrainLayer )
26. {
27.     // add the terrain layer to the terrain before filling
28.     AddTerrainLayer( terrain, terrainLayer );
29.  
30.     // get the weight data for the alphamaps
31.     int width = terrain.terrainData.alphamapWidth;
32.     int height = terrain.terrainData.alphamapHeight;
33.     float[ , , ] alphamaps = terrain.terrainData.GetAlphaMaps( 0, 0, width, height );
34.  
35.     int numAlphamaps = alphamaps.GetCount( 2 );
36.     for( int i = 0; i < numAlphamaps; ++i )
37.     {
38.         // TODO: loop through the alphamaps and set weights for your filled
39.         //       terrain layer to 1 and all other terrain layers to 0
40.     }
41.  
42.     // NOTE: normally you'd have to renormalize the weights but since you
43.     //       are filling the weights of one layer and clearing the rest, you can
44.     //       skip that step since they will technically be normalized
45.  
46.     // NOTE: probably want to track Undo step here before modifying the TerrainData
47.  
48.     // set the new alphamap weights in the terrain data
49.     terrainData.SetAlphamaps( 0, 0, alphamaps );
50. }

Does this better answer your question?

 

Using a PaintContext can be faster as that is done on the GPU