Terrain Manager Script

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class TerrainManager : MonoBehaviour, ICameraObserver {

    public Terrain mainTerrain;
    public float terrainChangeRate = 0.0001f;
    public int brushArea = 20;
    public static int viewDistance = 9;
    public static Vector2 VECTOR_WILDCARD = new Vector2(-10000, -10000);

    int resolutionX;
    int resolutionY;
    float[,] heights;
    int heightEdit = 1;

    //Chunks
    List<Vector2> loadedChunks = new List<Vector2>();
    Vector2[] visibleChunks = null;
    Terrain[] chunkGraphics = new Terrain[viewDistance];
    Vector2 curChunkIndex = new Vector2();
    int chunkSizeX = 256;
    int chunkSizeY = 256;

    // Use this for initialization
    void Start () {
        resolutionX = mainTerrain.terrainData.heightmapWidth;
        resolutionY = mainTerrain.terrainData.heightmapHeight;

        heights = mainTerrain.terrainData.GetHeights(0, 0, resolutionX, resolutionY);

        Camera.main.GetComponent<RTSCamera>().Subscribe(this);
        GameObject world = new GameObject();
        world.name = "World";

        for (int i = 0; i < viewDistance; i++)
        {
            GameObject go = new GameObject();
            go.name = "Chunk_" + i;
            go.transform.SetParent(world.transform);

            chunkGraphics[i] = go.AddComponent<Terrain>();

            chunkGraphics[i].terrainData = new TerrainData();
            go.AddComponent<TerrainCollider>().terrainData = chunkGraphics[i].terrainData;

            chunkGraphics[i].terrainData.size = new Vector3((int)(chunkSizeX / 4), 600, (int)(chunkSizeY / 4));
            chunkGraphics[i].terrainData.heightmapResolution = (int)(chunkSizeX / 2);
        }
        onCameraMove(Camera.main.transform.position);
    }

    // Update is called once per frame
    void Update () {
        if (Input.GetMouseButton(0))
        {
            RaycastHit hit;
            Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
            if (Physics.Raycast(ray, out hit))
            {
                editTerrainHeight(hit.point, terrainChangeRate, brushArea);
            }
        }
    }

    void editTerrainHeight(Vector3 position, float amount, int diameter)
    {
        int terrainPosX = (int)((position.x / mainTerrain.terrainData.size.x) * resolutionX);
        int terrainPosY = (int)((position.z / mainTerrain.terrainData.size.z) * resolutionY);

        float[,] heightChange = new float[diameter, diameter];

        int radius = diameter / 2;

        if (Input.GetKey(KeyCode.LeftShift))
        {
            heightEdit = -1;
        }
        else
        {
            heightEdit = 1;
        }
        amount = amount * heightEdit;

        for (int x = 0; x < diameter; x++)
        {
            for (int y = 0; y < diameter; y++)
            {
                int x2 = x - radius;
                int y2 = y - radius;
                heightChange[y, x] = heights[terrainPosY + y2, terrainPosX + x2] + amount;
                heights[terrainPosY + y2, terrainPosX + x2] = heightChange[y, x];
            }
        }

        mainTerrain.terrainData.SetHeights(terrainPosX - radius, terrainPosY - radius, heightChange);
    }

    public void onCameraMove(Vector3 newCameraPosition)
    {
        int chunkIndexX = Mathf.FloorToInt(newCameraPosition.x / chunkSizeX);
        int chunkIndexY = Mathf.FloorToInt(newCameraPosition.z / chunkSizeY);

        if (curChunkIndex.x == chunkIndexX && curChunkIndex.y == chunkIndexY)
        {
            return;
        }

        curChunkIndex.x = chunkIndexX;
        curChunkIndex.y = chunkIndexY;

        Vector2[] newVisibleChunks = new Vector2[viewDistance];

        newVisibleChunks[0] = new Vector2(chunkIndexX - 1, chunkIndexY +1);
        newVisibleChunks[1] = new Vector2(chunkIndexX, chunkIndexY +1);
        newVisibleChunks[2] = new Vector2(chunkIndexX + 1, chunkIndexY +1);

        newVisibleChunks[3] = new Vector2(chunkIndexX -1, chunkIndexY);
        newVisibleChunks[4] = new Vector2(chunkIndexX, chunkIndexY);
        newVisibleChunks[5] = new Vector2(chunkIndexX + 1, chunkIndexY);

        newVisibleChunks[6] = new Vector2(chunkIndexX - 1, chunkIndexY -1);
        newVisibleChunks[7] = new Vector2(chunkIndexX, chunkIndexY -1);
        newVisibleChunks[8] = new Vector2(chunkIndexX + 1, chunkIndexY -1);

        Terrain[] newChunkGraphics = new Terrain[viewDistance];
        List<int> freeTerrains = new List<int>();
        List<int> loadingIndexes = new List<int>();

        for (int i = 0; i < viewDistance; i++)
        {
            bool found = false;

            for (int j = 0; j < viewDistance; j++)
            {
                if (visibleChunks == null)
                {
                    break;
                }
                if (newVisibleChunks[i].Equals(visibleChunks[j]))
                {
                    visibleChunks[j] = VECTOR_WILDCARD;
                    newChunkGraphics[i] = chunkGraphics[j];

                    found = true;
                    break;
                }
            }
            if (!found)
            {
                loadingIndexes.Add(i);
            }
        }

        if (visibleChunks != null)
        {
            for (int i = 0; i < viewDistance; i++)
            {
                if (visibleChunks[i] != VECTOR_WILDCARD)
                {
                    freeTerrains.Add(i);
                    saveChunkToMemory(chunkGraphics[i], visibleChunks[i]);
                }
            }
        }
        else
        {
            for (int i = 0; i < viewDistance; i++)
            {
                    freeTerrains.Add(i);
            }
        }

        for (int i = 0; i < loadingIndexes.Count; i++)
        {
            loadChunkFromMemory(newVisibleChunks[loadingIndexes[i]], freeTerrains[i]);
            newChunkGraphics[loadingIndexes[i]] = chunkGraphics[freeTerrains[i]];
        }

        visibleChunks = newVisibleChunks;
        chunkGraphics = newChunkGraphics;
    }

    void loadChunkFromMemory(Vector2 cordIndex, int graphicIndex)
    {
        bool found = false;
        foreach (Vector2 v in loadedChunks)
        {
            if (v == cordIndex)
            {
                found = true;
                break;
            }
        }
        GameObject terrainGO;
        if (!found)
        {
            terrainGO = generateChunk(cordIndex, graphicIndex);
        }
        else
        {
            //Load Chunk from Memory
            Debug.Log("Loading Chunk(" + cordIndex.x + "," + cordIndex.y + ")");

            terrainGO = chunkGraphics[graphicIndex].gameObject;
        }

        terrainGO.transform.position = new Vector3(chunkSizeX * cordIndex.x, 0, chunkSizeY * cordIndex.y);


    }

    GameObject generateChunk(Vector2 cordIndex, int graphicIndex)
    {
        GameObject terrainGO = chunkGraphics[graphicIndex].gameObject;

        loadedChunks.Add(cordIndex);

        setTerrainHeightMap(terrainGO.GetComponent<Terrain>(), cordIndex);

        return terrainGO;
    }

    void setTerrainHeightMap(Terrain terrain, Vector2 cordIndex)
    {
        float[,] heights = new float[terrain.terrainData.heightmapHeight, terrain.terrainData.heightmapWidth];

        heights[0, 0] = 0.5f;
        heights[terrain.terrainData.heightmapWidth - 1, 0] = 0.5f;
        heights[0, terrain.terrainData.heightmapHeight - 1] = 0.5f;
        heights[terrain.terrainData.heightmapWidth - 1, terrain.terrainData.heightmapHeight - 1] = 0.5f;

        heights = diamondSquare(heights, 0, 0, terrain.terrainData.heightmapWidth - 1, 0);

        terrain.terrainData.SetHeights(0, 0, heights);
    }

    float[,] getTerrainHeightMap(Vector2 cordIndex)
    {
          return null;
    }

    float[,] diamondSquare(float[,] heights, int offSetX, int offSetY, int squareSize, int depth)
    {
        if (squareSize == 1)
        {
            return heights;
        }

        float topLeft = heights[offSetY, offSetX];
        float topRight = heights[offSetY, offSetX + squareSize];
        float bottomLeft = heights[offSetY + squareSize, offSetX];
        float bottomRight = heights[offSetY + squareSize, offSetX + squareSize];

        int size = squareSize / 2;

        if (topLeft == 0 || topRight == 0 || bottomLeft == 0 || bottomRight == 0)
        {
            Debug.LogError("One or more Corner Seeds have not been set..");
        }

        if (heights[offSetY + size, offSetX + size] == 0)
        {
            heights[offSetY + size, offSetX + size] = getRandomHeight(depth + (int)averagePoints(topLeft, topRight, bottomLeft, bottomRight));
        }
        float centrePoint = heights[offSetY + size, offSetX + size];

        //left Diamond
        float runningAverage = averagePoints(topLeft, centrePoint, bottomLeft);

        if (offSetX - size > 0 && heights[offSetY + size, offSetX - size] != 0)
        {
            runningAverage = averagePoints(topLeft, centrePoint, bottomLeft, heights[offSetY + size, offSetX - size]);
        }

        if (heights[offSetY + size, offSetX] == 0)
        {
            heights[offSetY + size, offSetX] = runningAverage + getRandomHeight(depth);
        }

        //right Diamond
        runningAverage = averagePoints(topRight, centrePoint, bottomRight);

        if (offSetX + (squareSize * 1.5f) < heights.GetLength(1) && heights[offSetY + size, offSetX + (int)(squareSize * 1.5f)] != 0)
        {
            runningAverage = averagePoints(topRight, centrePoint, bottomRight, heights[offSetY + size, offSetX + (int)(squareSize * 1.5f)]);
        }

        if (heights[offSetY + size, offSetX + squareSize] == 0)
        {
            heights[offSetY + size, offSetX + squareSize] = runningAverage + getRandomHeight(depth);
        }

        //top Diamond
        runningAverage = averagePoints(topLeft, centrePoint, topRight);

        if (offSetY - size > 0 && heights[offSetY - size, offSetX + size] != 0)
        {
            runningAverage = averagePoints(topLeft, centrePoint, topRight, heights[offSetY - size, offSetX + size]);
        }

        if (heights[offSetY, offSetX + size] == 0)
        {
            heights[offSetY, offSetX + size] = runningAverage + getRandomHeight(depth);
        }

        //bottom Diamond
        runningAverage = averagePoints(bottomRight, centrePoint, bottomLeft);

        if (offSetY + (squareSize * 1.5f) < heights.GetLength(0) && heights[offSetY + (int)(squareSize * 1.5f), offSetX + size] != 0)
        {
            runningAverage = averagePoints(bottomRight, centrePoint, topRight, heights[offSetY + (int)(squareSize * 1.5f), offSetX + size]);
        }

        if (heights[offSetY + squareSize, offSetX + size] == 0)
        {
            heights[offSetY + squareSize, offSetX + size] = runningAverage + getRandomHeight(depth);
        }

        heights = diamondSquare(heights, offSetX, offSetY, size, depth + 1);
        heights = diamondSquare(heights, offSetX + size, offSetY, size, depth + 1);
        heights = diamondSquare(heights, offSetX, offSetY + size, size, depth + 1);
        heights = diamondSquare(heights, offSetX + size, offSetY + size, size, depth + 1);

        return heights;

     }

    float averagePoints(float p1, float p2, float p3, float p4)
    {
        return (p1 + p2 + p3 + p4) * 0.25f;
    }

    float averagePoints(float p1, float p2, float p3)
    {
        return (p1 + p2 + p3) * 0.3333f;
    }

    float getRandomHeight(int depth)
    {
        return Random.Range(-0.1f, 0.0f) / Mathf.Pow(2, depth);
    }

    void saveChunkToMemory(Terrain chunk, Vector2 index)
    {
        Debug.Log("Unloading Chunk(" + index.x + "," + index.y + ")");
    }
}