Some Terrain Wizards for Unity

using UnityEditor;
using UnityEngine;
using System.IO;

// various terrain helper tools, a collection of wizards!

public class SplatmapWizard : ScriptableWizard
{
    public Terrain targetTerrain;
    public Texture2D customSplatmap;

    private TerrainData data;
    private int w;

    [MenuItem("Terrain/Replace Splatmap...")]
    static void CreateWizard ()
    {
        var wiz = ScriptableWizard.DisplayWizard<SplatmapWizard>("Custom Splatmap", "Replace");
        wiz.targetTerrain = Terrain.activeTerrain;
    }


    void OnWizardCreate ()
    {
        data = targetTerrain.terrainData;
        int w = data.alphamapWidth;
        //data.alphamapResolution = data.GetAlphamaps(0,0,w,w);

        float[,,] splatmapData = data.GetAlphamaps(0, 0, w, w);
        Color[] mapColors = customSplatmap.GetPixels();

        int numSplatMaps = splatmapData.GetLength(2);

        for (int z=0; z<numSplatMaps; ++z)
        {
            for (int y=0; y<w; ++y)
            {
                for (int x=0; x<w; ++x)
                {
                    splatmapData[x,y,z] = mapColors[x*w + y][z];
                }
            }
        }

        data.SetAlphamaps(0, 0, splatmapData);
    }

}


public class GetSplatmapWizard : ScriptableWizard
{
    public Terrain terrain;
    public Texture2D targetTexture;

    private TerrainData data;
    private int w;

    [MenuItem("Terrain/Get Texture From Splatmap...")]
    static void CreateWizard ()
    {
        var wiz = ScriptableWizard.DisplayWizard<GetSplatmapWizard>("Custom Splatmap", "Get");
        wiz.terrain = Terrain.activeTerrain;
    }


    void OnWizardCreate ()
    {
        data = terrain.terrainData;
        int w = data.alphamapWidth;
        //data.alphamapResolution = data.GetAlphamaps(0,0,w,w);

        float[,,] splatmapData = data.GetAlphamaps(0, 0, w, w);
        Color[] mapColors = targetTexture.GetPixels();

        int numSplatMaps = splatmapData.GetLength(2);

        for (int z=0; z<numSplatMaps; ++z)
        {
            for (int y=0; y<w; ++y)
            {
                for (int x=0; x<w; ++x)
                {
                    mapColors[x*w + y][z] = splatmapData[x,y,z];
                }
            }
        }

        targetTexture.SetPixels( mapColors );
        var bytes = targetTexture.EncodeToPNG();
        File.WriteAllBytes(Application.dataPath + "/"+targetTexture.name+".png", bytes);


    }
}


public class FlattenTerrainEdgeWizard : ScriptableWizard
{
    public Terrain terrain;
    public float flattenToHeight;
    private TerrainData data;
    private int w;

    [MenuItem("Terrain/Flatten Terrain Edge...")]
    static void CreateWizard ()
    {
        var wiz = ScriptableWizard.DisplayWizard<FlattenTerrainEdgeWizard>("Flatten Terrain Edge", "Apply");

        wiz.terrain = Terrain.activeTerrain;
    }


    void OnWizardCreate ()
    {
        data = terrain.terrainData;
        int w = data.heightmapResolution;
        float[,] heights = data.GetHeights(0,0,w,w);

        for (int y=0; y<w; y += 1)
        {
            for (int x=0; x<w; x += 1)
            {
                if (x==0 || y==0 || x==w-1 || y==w-1)   heights[x,y] = flattenToHeight;
            }
        }

        data.SetHeights(0,0,heights);

    }

}



public class RaiseLowerTerrainWizard : ScriptableWizard
{
    public Terrain terrain;
    public float amount;
    private TerrainData data;
    private int w;

    [MenuItem("Terrain/Raise or Lower Terrain...")]
    static void CreateWizard ()
    {
        var wiz = ScriptableWizard.DisplayWizard<RaiseLowerTerrainWizard>("Raise or Lower Terrain", "Apply");
        wiz.terrain = Terrain.activeTerrain;
    }


    void OnWizardCreate ()
    {
        data = terrain.terrainData;
        int w = data.heightmapResolution;
        float[,] heights = data.GetHeights(0,0,w,w);

        amount /= data.heightmapScale.y;

        for (int y=0; y<w; ++y)
        {
            for (int x=0; x<w; ++x)
            {
                heights[x,y] += amount;
            }
        }

        data.SetHeights(0,0,heights);

    }

}

public class GroundAndAlignToTerrain : ScriptableWizard
{
    public Terrain terrain;
    public bool alignRotationToSurface = true;
    public float upwardsOffset = 0;
    public bool randomYRotation = false;

    [MenuItem("Terrain/Ground and align selected objects to Terrain...")]
    static void CreateWizard ()
    {
        var wiz = ScriptableWizard.DisplayWizard<GroundAndAlignToTerrain>("Ground and align selected objects to Terrain", "Apply");
        wiz.terrain = Terrain.activeTerrain;
    }


    void OnWizardCreate ()
    {
        foreach (var obj in Selection.gameObjects)
        {
            Vector3 pos = obj.transform.position;
            float height = terrain.SampleHeight(pos);
            float x = pos.x-terrain.transform.position.x;
            float z = pos.z-terrain.transform.position.z;
            Vector3 up = terrain.terrainData.GetInterpolatedNormal(x,z);

            pos.y = height;
            obj.transform.position = pos;
            if (alignRotationToSurface)
            {
                obj.transform.rotation = Quaternion.LookRotation( obj.transform.forward, up );
            }
            obj.transform.Translate( 0, upwardsOffset, 0, Space.Self );
        }

    }

}