Top Down 2D Random Terrain

Hello Unity community, I've been struggling with trying to figure out how to create random top-down terrain.
I'm not trying to create complete randomness, where each tile is just random, but more procedurally generated terrain in C#.
I've tried doing two for loops, but didn't know how to randomize it.
Here's what I have:
(By the way, I have 3 GameObjects: Grass, Stone, and Water.
The following code works but I need to know how to add the rest of the GameObjects and make it procedurally random. Also, just in case you were wondering, my textures are 64x64)

Code (CSharp):

1.  
2.     public GameObject Grass;
3.     public GameObject Stone;
4.     public GameObject Water;
5.  
6.     public int x_length;
7.     public int y_length;
8.  
9.     void Start () {
10.         for(int x = 0; x < x_length; x++){
11.             for(int y = 0; y < y_length; y++){
12.                 GameObject currentObject = Instantiate(Grass,new Vector3(0,0,0),Quaternion.identity) as GameObject;
13.                 currentObject.transform.localPosition = new Vector3(x*0.64f,y*0.64f,0);
14.                 currentObject.transform.parent = transform;
15.                 currentObject.transform.name = "GrassTerrainPiece " + x + " " + y;
16.             }
17.         }
18.     }
19.  

 

Try putting the grass, stone and water objects into an array instead, then use a random index when instantiating

Code (CSharp):

1.    
2.        // public GameObject Grass;
3.        // public GameObject Stone;
4.        // public GameObject Water;
5.         public GameObject[] Tiles;
6.  
7.         public int x_length;
8.         public int y_length;
9.    
10.         void Start () {
11.             for(int x = 0; x < x_length; x++){
12.                 for(int y = 0; y < y_length; y++){
13.                     GameObject currentObject = Instantiate(Tiles[Random.Range(0,Tiles.Length)] ,new Vector3(0,0,0),Quaternion.identity) as GameObject;
14.                     currentObject.transform.localPosition = new Vector3(x*0.64f,y*0.64f,0);
15.                     currentObject.transform.parent = transform;
16.                     currentObject.transform.name = "RandomTerrainPiece " + x + " " + y;
17.                 }
18.             }
19.         }
20.    
21.  

 

Thanks for the answer.
However, how do I generate the terrain procedurally?

 

Ok, so instead of using Random.Range, you could use perlin noise
http://docs.unity3d.com/ScriptReference/Mathf.PerlinNoise.html
That way, its always generates the same every time

 

Could you give me an example of how to implement it into what I already have?

 

Here's some code which uses Perlin noise to create this. The relevant code is the nested loop in the CreateLevel function; as you can see there's not actually much to it. It's just two kinds of tiles but the idea could be extended to use more.

--Eric