Unity3D中的地形转成模型
起因
为什么要把地形转成模型呢？在Unity3D中创建地形很方便，用它自带的地形编辑工具，各种跌宕起伏的地形都能很容易的创建出来。但是也有一些不方便的地方，比如创建好的地形不能整体缩放，只能通过修改长宽等参数进行调整。偏偏就有这样的需求，我们要把地形放到虚拟研讨厅的桌子上当做数字沙盘去展示。如果把地形对象的长宽高都缩小的话，高度图也要缩小，地形效果就太不好了。如果地形对象能像模型对象一样，随意的缩放就好了。
解决方法
终于在网上找到了解决方法，有大神贡献了一个脚本，能够把地形对象转换成模型对象，模型格式为obj，可以直接导入到Unity3D中使用。
using UnityEngine;
using UnityEditor;
using System;
using System.Collections;
using System.IO;using System.Text;
enum SaveFormat { Triangles, Quads }
enum SaveResolution { Full=0, Half, Quarter, Eighth, Sixteenth }
class ExportTerrain : EditorWindow
{
SaveFormat saveFormat = SaveFormat.Triangles;
SaveResolution saveResolution = SaveResolution.Half;
static TerrainData terrain;
static Vector3 terrainPos;
int tCount;
int counter;
int totalCount;
int progressUpdateInterval = 10000;
[MenuItem("Terrain/Export To Obj...")]
static void Init()
{
terrain = null;
Terrain terrainObject = Selection.activeObject as Terrain;
if (!terrainObject)
{
terrainObject = Terrain.activeTerrain;
}
if (terrainObject)
{
terrain = terrainObject.terrainData;
terrainPos = terrainObject.transform.position;
}
EditorWindow.GetWindow<ExportTerrain>().Show();
}
void OnGUI()
{
if (!terrain)
{
GUILayout.Label("No terrain found");
if (GUILayout.Button("Cancel"))
{
EditorWindow.GetWindow<ExportTerrain>().Close();
}
return;
}
saveFormat = (SaveFormat) EditorGUILayout.EnumPopup("Export Format", saveFormat);
saveResolution = (SaveResolution) EditorGUILayout.EnumPopup("Resolution", saveResolution);
if (GUILayout.Button("Export"))
{
Export();
}
}
void Export()
{
string fileName = EditorUtility.SaveFilePanel("Export .obj file", "", "Terrain", "obj");
int w = terrain.heightmapWidth;
int h = terrain.heightmapHeight;
Vector3 meshScale = terrain.size;
int tRes = (int)Mathf.Pow(2, (int)saveResolution );
meshScale = new Vector3(meshScale.x / (w - 1) * tRes, meshScale.y, meshScale.z / (h - 1) * tRes);
Vector2 uvScale = new Vector2(1.0f / (w - 1), 1.0f / (h - 1));
float[,] tData = terrain.GetHeights(0, 0, w, h);
w = (w - 1) / tRes + 1;
h = (h - 1) / tRes + 1;
Vector3[] tVertices = new Vector3[w * h];
Vector2[] tUV = new Vector2[w * h];
int[] tPolys;
if (saveFormat == SaveFormat.Triangles)
{
tPolys = new int[(w - 1) * (h - 1) * 6];
}
else
{
tPolys = new int[(w - 1) * (h - 1) * 4];
}
// Build vertices and UVs
for (int y = 0; y < h; y++)
{
for (int x = 0; x < w; x++)
{
tVertices[y * w + x] = Vector3.Scale(meshScale, new Vector3(-y, tData[x * tRes, y * tRes], x)) + terrainPos;
tUV[y * w + x] = Vector2.Scale( new Vector2(x * tRes, y * tRes), uvScale);
}
}
int index = 0;
if (saveFormat == SaveFormat.Triangles)
{
// Build triangle indices: 3 indices into vertex array for each triangle
for (int y = 0; y < h - 1; y++)
{
for (int x = 0; x < w - 1; x++)
{
// For each grid cell output two triangles
tPolys[index++] = (y * w) + x;
tPolys[index++] = ((y + 1) * w) + x;
tPolys[index++] = (y * w) + x + 1;
tPolys[index++] = ((y + 1) * w) + x;
tPolys[index++] = ((y + 1) * w) + x + 1;
tPolys[index++] = (y * w) + x + 1;
}
}
}
else
{
// Build quad indices: 4 indices into vertex array for each quad
for (int y = 0; y < h - 1; y++)
{
for (int x = 0; x < w - 1; x++)
{
// For each grid cell output one quad
tPolys[index++] = (y * w) + x;
tPolys[index++] = ((y + 1) * w) + x;
tPolys[index++] = ((y + 1) * w) + x + 1;
tPolys[index++] = (y * w) + x + 1;
}
}
}
// Export to .obj
StreamWriter sw = new StreamWriter(fileName);
try
{
sw.WriteLine("# Unity terrain OBJ File");
// Write vertices
System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("en-US");
counter = tCount = 0;
totalCount = (tVertices.Length * 2 + (saveFormat == SaveFormat.Triangles ? tPolys.Length / 3 : tPolys.Length / 4)) / progressUpdateInterval;
for (int i = 0; i < tVertices.Length; i++)
{
UpdateProgress();
StringBuilder sb = new StringBuilder("v ", 20);
// StringBuilder stuff is done this way because it's faster than using the "{0} {1} {2}"etc. format
// Which is important when you're exporting huge terrains.
sb.Append(tVertices[i].x.ToString()).Append(" ").
Append(tVertices[i].y.ToString()).Append(" ").
Append(tVertices[i].z.ToString());
sw.WriteLine(sb);
}
// Write UVs
for (int i = 0; i < tUV.Length; i++)
{
UpdateProgress();
StringBuilder sb = new StringBuilder("vt ", 22);
sb.Append(tUV[i].x.ToString()).Append(" ").
Append(tUV[i].y.ToString());
sw.WriteLine(sb);
}
if (saveFormat == SaveFormat.Triangles)
{
// Write triangles
for (int i = 0; i < tPolys.Length; i += 3)
{
UpdateProgress();
StringBuilder sb = new StringBuilder("f ", 43);
sb.Append(tPolys[i] + 1).Append("/").Append(tPolys[i] + 1).Append(" ").
Append(tPolys[i + 1] + 1).Append("/").Append(tPolys[i + 1] + 1).Append(" ").
Append(tPolys[i + 2] + 1).Append("/").Append(tPolys[i + 2] + 1);
sw.WriteLine(sb);
}
}
else
{
// Write quads
for (int i = 0; i < tPolys.Length; i += 4)
{
UpdateProgress();
StringBuilder sb = new StringBuilder("f ", 57);
sb.Append(tPolys[i] + 1).Append("/").Append(tPolys[i] + 1).Append(" ").
Append(tPolys[i + 1] + 1).Append("/").Append(tPolys[i + 1] + 1).Append(" ").
Append(tPolys[i + 2] + 1).Append("/").Append(tPolys[i + 2] + 1).Append(" ").
Append(tPolys[i + 3] + 1).Append("/").Append(tPolys[i + 3] + 1);
sw.WriteLine(sb);
}
}
}
catch(Exception err)
{
Debug.Log("Error saving file: " + err.Message);
}
sw.Close();
terrain = null;
EditorUtility.DisplayProgressBar("Saving file to disc.", "This might take a while...", 1f);
EditorWindow.GetWindow<ExportTerrain>().Close();
EditorUtility.ClearProgressBar();
}
void UpdateProgress()
{
if (counter++ == progressUpdateInterval)
{
counter = 0;
EditorUtility.DisplayProgressBar("Saving...", "", Mathf.InverseLerp(0, totalCount, ++tCount));
}
}
}
使用方法
给脚本命名为ExportTerrain.cs。
这个脚本文件一定要放到工程中Assets文件夹下面的Editor文件夹中（没有的话自己创建）才能正常工作。
完成前两步之后，unity菜单项会多出一个Terrain/Export To Obj...的菜单(4.3以前的版本本来就有Terrain菜单，只是多了个子菜单；4.3版本里面默认没有Terrain菜单了)。
terrain-menu
选择场景要转成模型的地形对象。如果什么都没选的话，会使用默认的active terrain。
然后选择Terrain/Export To Obj...菜单，弹出下面的对话框，选择导出格式（triangles or quads）、Mesh分辨率（full, half, quarter, eighth or sixteenth）、文件名和路径，然后点击Export。
terrain-expoty
等待进度条跑完之后就OK了，obj文件就导出成功了。
See Also
和地形转模型的方法相反的一个操作，还有模型转地形的方法，类似的也是有脚本完成的，感兴趣可以参考Object2Terrain[2].
参考
http://wiki.unity3d.com/index.php?title=TerrainObjExporter
http://wiki.unity3d.com/index.php?title=Object2Terrain
