Vector3 terrainPos = hit - terrain.transform.position;
        Vector3 splatMapPos = new Vector3(
            terrainPos.x / Terrain.terrainData.size.x,
            0,
            terrainPos.z / Terrain.terrainData.size.z
        );

        int x = Mathf.FloorToInt(splatMapPos.x * Terrain.terrainData.alphamapWidth);
        int z = Mathf.FloorToInt(splatMapPos.z * Terrain.terrainData.alphamapHeight);

        float[,,] alphaMap = Terrain.terrainData.GetAlphamaps(x, z, 1, 1);