UnityのTerrainの平行移動とか

TerrainEditor.cs

using UnityEngine;
using UnityEditor;
using System;
using System.Reflection;
using System.Linq;
using System.Collections.Generic;

public class TerrainEditor : EditorWindow
{
    int moveX = 10;
    int moveY = 10;
    int width, height;
    public TerrainData target;

    [MenuItem("Window/Terrain Editor")]
    static void OpenTerrainEditor()
    {
        var window = EditorWindow.GetWindow<TerrainEditor>("Terrain Editor");
        window.target = Selection.activeObject as TerrainData;
    }

    void OnGUI()
    {
        target = EditorGUILayout.ObjectField(target, typeof(TerrainData), false) as TerrainData;
        if (target != null)
        {
            EditorGUILayout.LabelField("Size", "(" + target.heightmapWidth + ", " + target.heightmapHeight + ")");
            moveX = EditorGUILayout.IntField("Move X", moveX);
            moveY = EditorGUILayout.IntField("Move Y", moveY);
            if (GUILayout.Button("Move"))
            {
                MoveTerrain(target, moveX, moveY);
            }
        }
    }

    public static void MoveTerrain(TerrainData terrain, int x, int y)
    {
        var so = new SerializedObject(terrain);
        var editeds = new List<UnityEngine.Object>();

        // Undo
        var textures = so.FindProperty("m_SplatDatabase.m_AlphaTextures");
        for (int i = 0; i < textures.arraySize; i++)
        {
            editeds.Add(textures.GetArrayElementAtIndex(i).objectReferenceValue);
        }
        editeds.Add(terrain);
        Undo.RecordObjects(editeds.ToArray(), "Move Terrain");

        // Move Hightmap
        var w = terrain.heightmapWidth;
        var h = terrain.heightmapHeight;
        var heights = terrain.GetHeights(0, 0, w, h);
        terrain.SetHeights(0, 0, MoveHeights(heights, w, h, x, y));

        // Move Trees
        var moveU = (float)x / w;
        var moveV = (float)y / h;
        var trees = terrain.treeInstances;
        for (int i = 0; i < trees.Length; i++)
        {
            trees[i].position += new Vector3(moveU, 0f, moveV);
        }
        terrain.treeInstances = trees.Where(tree =>
            0f <= tree.position.x && tree.position.x <= 1f
            && 0f <= tree.position.z && tree.position.z <= 1f).ToArray();

        // Move Details

        // Move Splat
        for (int i = 0; i < textures.arraySize; i++)
        {
            var tex = textures.GetArrayElementAtIndex(i).objectReferenceValue as Texture2D;
            editeds.Add(tex);
            MoveTexture(tex, moveU, moveV);
        }
    }

    static float[,] MoveHeights(float[,] map,
                                int width, int height, int moveX, int moveY)
    {
        var result = new float[width, height];
        for (int y = 0; y < height; y++)
        {
            for (int x = 0; x < width; x++)
            {
                var srcX = x - moveX;
                var srcY = y - moveY;
                if (0 <= srcX && srcX < width && 0 <= srcY && srcY < height)
                    result[y, x] = map[srcY, srcX];
                else
                    result[y, x] = 0;
            }
        }
        return result;
    }

    static void MoveTexture(Texture2D texture, float u, float v)
    {
        Color[] colors = new Color[texture.width * texture.height];
        var uUnit = 1f / texture.width;
        var vUnit = 1f / texture.height;
        for (int y = 0; y < texture.width; y++)
        {
            for (int x = 0; x < texture.height; x++)
            {
                var dst = y * texture.width + x;
                var srcU = (x + 0.5f) * uUnit - u;
                var srcV = (y + 0.5f) * vUnit - v;
                colors[dst] = texture.GetPixelBilinear(srcU, srcV);
            }
        }
        texture.SetPixels(colors);
        texture.Apply();
    }
}