36. 更换unity terrain的地表贴图

设置alphamap的核心方法是TerrainData的SetAlphamaps方法，关键参数是alpha三维数组。它的前两维表示了splatmap的大小，最后一维表示layer数目，也就是所使用的splatmap的通道数

using UnityEngine;

public class Example : MonoBehaviour
{
    public Terrain t;
    // Blend the two terrain textures according to the steepness of
    // the slope at each point.
    void Start()
    {
        float[,,] map = new float[t.terrainData.alphamapWidth, t.terrainData.alphamapHeight, 2];

        // For each point on the alphamap...
        for (int y = 0; y < t.terrainData.alphamapHeight; y++)
        {
            for (int x = 0; x < t.terrainData.alphamapWidth; x++)
            {

                map[x, y, 0] = 0;
                map[x, y, 1] = 1;
            }
        }
        t.terrainData.SetAlphamaps(0, 0, map);
    }
}