我把var terrainHeights = Terrain.activeTerrain.terrainData.GetHeights( 0, 0, xPolyDivision, zPolyDivision);

改为var terrainHeights = GetComponent(Terrain).terrainData.GetHeights( 0, 0, xPolyDivision, zPolyDivision);

这句报错：terrainHeights[i,j] = hit.point.y/Terrain.activeTerrain.terrainData.size.y;

不明白是什么原因。为什么用activeTerrain就可以呢？？ 当我在场景中创建一个Terrain时，还不都是指向同一个Terrain吗？？请高手指教！！

看来在unity3d中制作地形的方法有多了一种，那就是直接用一段程序来生成地形，这个好像很方便，不过本机测试时，导入作者提供的资源包，却没成功，不知是什么原因。有兴趣的朋友可以试试！
So I’ve been working on a simple procedural terrain script in the Unity engine. It currently defines a 2D array of floats, then assigns random values within a certain range. I then call a function that adds rows and collumns between the existing data points, generating midpoints. These midpoints are then given a new value based on the average of the two points on either side with an added noise value.