u3d change terrain textrue&height

using UnityEngine;
using System.Collections;

public class terrainTest : MonoBehaviour
{
    public int terrainDeformationTextureNum = 1;
    private Terrain terr; // terrain to modify
    protected int hmWidth; // heightmap width
    protected int hmHeight; // heightmap height
    protected int alphaMapWidth;
    protected int alphaMapHeight;
    protected int numOfAlphaLayers;
    protected const float DEPTH_METER_CONVERT = 0.05f;
    protected const float TEXTURE_SIZE_MULTIPLIER = 1.25f;
    private float[,] heightMapBackup;
    private float[, ,] alphaMapBackup;

    void Start()
    {
        terr = this.GetComponent<Terrain>();
        hmWidth = terr.terrainData.heightmapWidth;
        hmHeight = terr.terrainData.heightmapHeight;
        alphaMapWidth = terr.terrainData.alphamapWidth;
        alphaMapHeight = terr.terrainData.alphamapHeight;
        numOfAlphaLayers = terr.terrainData.alphamapLayers;
        if (Debug.isDebugBuild)
        {
            heightMapBackup = terr.terrainData.GetHeights(0, 0, hmWidth, hmHeight);
            alphaMapBackup = terr.terrainData.GetAlphamaps(0, 0, alphaMapWidth, alphaMapHeight);
        }
    }


    
    //this has to be done because terrains for some reason or another terrains don't reset after you run the app
    void OnApplicationQuit()
    {
        if (Debug.isDebugBuild)
        {
            terr.terrainData.SetHeights(0, 0, heightMapBackup);
            terr.terrainData.SetAlphamaps(0, 0, alphaMapBackup);
        }
    }

    public void DestroyTerrain(Vector3 pos, float craterSizeInMeters)
    {
        DeformTerrain(pos, craterSizeInMeters);
        TextureDeformation(pos, craterSizeInMeters * 1.5f);
    }

    public void DeformTerrain(Vector3 pos, float craterSizeInMeters)
    {
        //get the heights only once keep it and reuse, precalculate as much as possible
        Vector3 terrainPos = GetRelativeTerrainPositionFromPos(pos, terr, hmWidth, hmHeight);//terr.terrainData.heightmapResolution/terr.terrainData.heightmapWidth
        int heightMapCraterWidth = (int)(craterSizeInMeters * (hmWidth / terr.terrainData.size.x));
        int heightMapCraterLength = (int)(craterSizeInMeters * (hmHeight / terr.terrainData.size.z));
        int heightMapStartPosX = (int)(terrainPos.x - (heightMapCraterWidth / 2));
        int heightMapStartPosZ = (int)(terrainPos.z - (heightMapCraterLength / 2));

        float[,] heights = terr.terrainData.GetHeights(heightMapStartPosX, heightMapStartPosZ, heightMapCraterWidth, heightMapCraterLength);
        float circlePosX;
        float circlePosY;
        float distanceFromCenter;
        float depthMultiplier;

        float deformationDepth = (craterSizeInMeters / 3.0f) / terr.terrainData.size.y;

        // we set each sample of the terrain in the size to the desired height
        for (int i = 0; i < heightMapCraterLength; i++) //width
        {
            for (int j = 0; j < heightMapCraterWidth; j++) //height
            {

                circlePosX = (j - (heightMapCraterWidth / 2)) / (hmWidth / terr.terrainData.size.x);
                circlePosY = (i - (heightMapCraterLength / 2)) / (hmHeight / terr.terrainData.size.z);
                distanceFromCenter = Mathf.Abs(Mathf.Sqrt(circlePosX * circlePosX + circlePosY * circlePosY));
                //convert back to values without skew

                if (distanceFromCenter < (craterSizeInMeters / 2.0f))
                {
                    depthMultiplier = ((craterSizeInMeters / 2.0f - distanceFromCenter) / (craterSizeInMeters / 2.0f));

                    depthMultiplier += 0.1f;
                    depthMultiplier += Random.value * .1f;

                    depthMultiplier = Mathf.Clamp(depthMultiplier, 0, 1);

                    if(heights[i,j] <0.1)

                    heights[i, j] = Mathf.Clamp(heights[i, j] +deformationDepth * depthMultiplier, 0, 1);

                }
            }
        }

        // set the new height
        terr.terrainData.SetHeights(heightMapStartPosX, heightMapStartPosZ, heights);
    }

    public void TextureDeformation(Vector3 pos, float craterSizeInMeters)
    {
        Vector3 alphaMapTerrainPos = GetRelativeTerrainPositionFromPos(pos, terr, alphaMapWidth, alphaMapHeight);
        int alphaMapCraterWidth = (int)(craterSizeInMeters * (alphaMapWidth / terr.terrainData.size.x));
        int alphaMapCraterLength = (int)(craterSizeInMeters * (alphaMapHeight / terr.terrainData.size.z));

        int alphaMapStartPosX = (int)(alphaMapTerrainPos.x - (alphaMapCraterWidth / 2));
        int alphaMapStartPosZ = (int)(alphaMapTerrainPos.z - (alphaMapCraterLength / 2));

        float[, ,] alphas = terr.terrainData.GetAlphamaps(alphaMapStartPosX, alphaMapStartPosZ, alphaMapCraterWidth, alphaMapCraterLength);

        float circlePosX;
        float circlePosY;
        float distanceFromCenter;

        for (int i = 0; i < alphaMapCraterLength; i++) //width
        {
            for (int j = 0; j < alphaMapCraterWidth; j++) //height
            {
                circlePosX = (j - (alphaMapCraterWidth / 2)) / (alphaMapWidth / terr.terrainData.size.x);
                circlePosY = (i - (alphaMapCraterLength / 2)) / (alphaMapHeight / terr.terrainData.size.z);

                //convert back to values without skew
                distanceFromCenter = Mathf.Abs(Mathf.Sqrt(circlePosX * circlePosX + circlePosY * circlePosY));


                if (distanceFromCenter < (craterSizeInMeters / 2.0f))
                {
                    for (int layerCount = 0; layerCount < numOfAlphaLayers; layerCount++)
                    {
                        //could add blending here in the future
                        if (layerCount == terrainDeformationTextureNum)
                        {
                            alphas[i, j, layerCount] = 1;
                        }
                        else
                        {
                            alphas[i, j, layerCount] = 0;
                        }
                    }
                }
            }
        }

        terr.terrainData.SetAlphamaps(alphaMapStartPosX, alphaMapStartPosZ, alphas);
    }

    protected Vector3 GetNormalizedPositionRelativeToTerrain(Vector3 pos, Terrain terrain)
    {
        //code based on: http://answers.unity3d.com/questions/3633/modifying-terrain-height-under-a-gameobject-at-runtime
        // get the normalized position of this game object relative to the terrain
        Vector3 tempCoord = (pos - terrain.gameObject.transform.position);
        Vector3 coord;
        coord.x = tempCoord.x / terr.terrainData.size.x;
        coord.y = tempCoord.y / terr.terrainData.size.y;
        coord.z = tempCoord.z / terr.terrainData.size.z;

        return coord;
    }

    protected Vector3 GetRelativeTerrainPositionFromPos(Vector3 pos, Terrain terrain, int mapWidth, int mapHeight)
    {
        Vector3 coord = GetNormalizedPositionRelativeToTerrain(pos, terrain);
        // get the position of the terrain heightmap where this game object is
        return new Vector3((coord.x * mapWidth), 0, (coord.z * mapHeight));
    }
}